Add new async_context abstraction and refactor cyw43_arch to use it (#1177)

* Extract all poll/threadsafe_background/freertos from cyw43_arch into new abstraction async_context:
* provides support for asynchronous events (timers/IRQ notifications) to be handled in a safe context.
* now guarantees all callbacks happen on a single core.
* is reusable by multiple different libraries (stdio_usb can now be ported to this but hasn't been yet).
* supports multiple independent instances (independent instances will not block each other).
* cyw43_arch libraries cleaned up to use the new abstraction. Note each distinct cyw43_arch type is now a very thin layer that creates the right type of context and adds cyw43_driver and lwip support as appropriate.

Additionally,

* Add new pico_time and hardware_alarm APIs
* Add from_us_since_boot()
* Add alarm_pool_create_with_unused_hardware_alarm()
* Add alarm_pool_add_alarm_at_force_in_context()
* Add hardware_alarm_claim_unused()
* Add hardware_alarm_force_irq()
* Added panic_compact() and some minor comment cleanup; moved FIRST_USER_IRQ define to platform_defs.h

docs/index.h

@@ -41,6 +41,7 @@
  * This group of libraries provide higher level functionality that isn't hardware related or provides a richer
  * set of functionality above the basic hardware interfaces
  * @{
+ * \defgroup pico_async_context pico_async_context
  * \defgroup pico_multicore pico_multicore
  * \defgroup pico_stdlib pico_stdlib
  * \defgroup pico_sync pico_sync
@@ -59,6 +60,7 @@
  * \defgroup networking Networking Libraries
  * Functions for implementing networking
  * @{
+ * \defgroup pico_cyw43_driver pico_cyw43_driver
  * \defgroup pico_lwip pico_lwip
  * \defgroup pico_cyw43_arch pico_cyw43_arch
  * @}

src/common/pico_base/include/pico/types.h

@@ -65,6 +65,18 @@ static inline void update_us_since_boot(absolute_time_t *t, uint64_t us_since_bo
 #endif
 }
 
+/*! fn from_us_since_boot
+ * \brief convert a number of microseconds since boot to an absolute_time_t
+ * \param us_since_boot number of microseconds since boot
+ * \return an absolute time equivalent to us_since_boot
+ * \ingroup timestamp
+ */
+static inline absolute_time_t from_us_since_boot(uint64_t us_since_boot) {
+    absolute_time_t t;
+    update_us_since_boot(&t, us_since_boot);
+    return t;
+}
+
 #ifdef NDEBUG
 #define ABSOLUTE_TIME_INITIALIZED_VAR(name, value) name = value
 #else

src/common/pico_time/include/pico/time.h

@@ -157,6 +157,17 @@ static inline int64_t absolute_time_diff_us(absolute_time_t from, absolute_time_
     return (int64_t)(to_us_since_boot(to) - to_us_since_boot(from));
 }
 
+/*! \brief Return the earlier of two timestamps
+ * \ingroup timestamp
+ *
+ * \param a the first timestamp
+ * \param b the second timestamp
+ * \return the earlier of the two timestamps
+ */
+static inline absolute_time_t absolute_time_min(absolute_time_t a, absolute_time_t b) {
+    return to_us_since_boot(a) < to_us_since_boot(b) ? a : b;
+}
+
 /*! \brief The timestamp representing the end of time; this is actually not the maximum possible
  * timestamp, but is set to 0x7fffffff_ffffffff microseconds to avoid sign overflows with time
  * arithmetic. This is almost 300,000 years, so should be sufficient.
@@ -397,6 +408,25 @@ alarm_pool_t *alarm_pool_get_default(void);
  */
 alarm_pool_t *alarm_pool_create(uint hardware_alarm_num, uint max_timers);
 
+/**
+ * \brief Create an alarm pool, claiming an used hardware alarm to back it.
+ *
+ * The alarm pool will call callbacks from an alarm IRQ Handler on the core of this function is called from.
+ *
+ * In many situations there is never any need for anything other than the default alarm pool, however you
+ * might want to create another if you want alarm callbacks on core 1 or require alarm pools of
+ * different priority (IRQ priority based preemption of callbacks)
+ *
+ * \note This method will hard assert if the there is no free hardware to claim.
+ *
+ * \ingroup alarm
+ * \param max_timers the maximum number of timers
+ *        \note For implementation reasons this is limited to PICO_PHEAP_MAX_ENTRIES which defaults to 255
+ * \sa alarm_pool_get_default()
+ * \sa hardware_claiming
+ */
+alarm_pool_t *alarm_pool_create_with_unused_hardware_alarm(uint max_timers);
+
 /**
  * \brief Return the hardware alarm used by an alarm pool
  * \ingroup alarm
@@ -446,6 +476,25 @@ void alarm_pool_destroy(alarm_pool_t *pool);
  */
 alarm_id_t alarm_pool_add_alarm_at(alarm_pool_t *pool, absolute_time_t time, alarm_callback_t callback, void *user_data, bool fire_if_past);
 
+/*!
+ * \brief Add an alarm callback to be called at or after a specific time
+ * \ingroup alarm
+ *
+ * The callback is called as soon as possible after the time specified from an IRQ handler
+ * on the core the alarm pool was created on. Unlike \ref alarm_pool_add_alarm_at, this method
+ * guarantees to call the callback from that core even if the time is during this method call or in the past.
+ *
+ * \note It is safe to call this method from an IRQ handler (including alarm callbacks), and from either core.
+ *
+ * @param pool the alarm pool to use for scheduling the callback (this determines which hardware alarm is used, and which core calls the callback)
+ * @param time the timestamp when (after which) the callback should fire
+ * @param callback the callback function
+ * @param user_data user data to pass to the callback function
+ * @return >0 the alarm id for an active (at the time of return) alarm
+ * @return -1 if there were no alarm slots available
+ */
+alarm_id_t alarm_pool_add_alarm_at_force_in_context(alarm_pool_t *pool, absolute_time_t time, alarm_callback_t callback,
+                                                    void *user_data);
 /*!
  * \brief Add an alarm callback to be called after a delay specified in microseconds
  * \ingroup alarm

src/common/pico_time/time.c

@@ -81,6 +81,7 @@ void alarm_pool_init_default() {
     if (!default_alarm_pool_initialized()) {
         ph_post_alloc_init(default_alarm_pool.heap, PICO_TIME_DEFAULT_ALARM_POOL_MAX_TIMERS,
                            timer_pool_entry_comparator, &default_alarm_pool);
+        hardware_alarm_claim(PICO_TIME_DEFAULT_ALARM_POOL_HARDWARE_ALARM_NUM);
         alarm_pool_post_alloc_init(&default_alarm_pool,
                                    PICO_TIME_DEFAULT_ALARM_POOL_HARDWARE_ALARM_NUM);
     }
@@ -181,12 +182,21 @@ alarm_pool_t *alarm_pool_create(uint hardware_alarm_num, uint max_timers) {
     pool->heap = ph_create(max_timers, timer_pool_entry_comparator, pool);
     pool->entries = (alarm_pool_entry_t *)calloc(max_timers, sizeof(alarm_pool_entry_t));
     pool->entry_ids_high = (uint8_t *)calloc(max_timers, sizeof(uint8_t));
+    hardware_alarm_claim(hardware_alarm_num);
     alarm_pool_post_alloc_init(pool, hardware_alarm_num);
     return pool;
 }
 
+alarm_pool_t *alarm_pool_create_with_unused_hardware_alarm(uint max_timers) {
+    alarm_pool_t *pool = (alarm_pool_t *) malloc(sizeof(alarm_pool_t));
+    pool->heap = ph_create(max_timers, timer_pool_entry_comparator, pool);
+    pool->entries = (alarm_pool_entry_t *)calloc(max_timers, sizeof(alarm_pool_entry_t));
+    pool->entry_ids_high = (uint8_t *)calloc(max_timers, sizeof(uint8_t));
+    alarm_pool_post_alloc_init(pool, (uint)hardware_alarm_claim_unused(true));
+    return pool;
+}
+
 void alarm_pool_post_alloc_init(alarm_pool_t *pool, uint hardware_alarm_num) {
-    hardware_alarm_claim(hardware_alarm_num);
     hardware_alarm_cancel(hardware_alarm_num);
     hardware_alarm_set_callback(hardware_alarm_num, alarm_pool_alarm_callback);
     pool->lock = spin_lock_instance(next_striped_spin_lock_num());
@@ -260,6 +270,26 @@ alarm_id_t alarm_pool_add_alarm_at(alarm_pool_t *pool, absolute_time_t time, ala
     return public_id;
 }
 
+alarm_id_t alarm_pool_add_alarm_at_force_in_context(alarm_pool_t *pool, absolute_time_t time, alarm_callback_t callback,
+                                                    void *user_data) {
+    bool missed = false;
+
+    uint8_t id_high = 0;
+    uint32_t save = spin_lock_blocking(pool->lock);
+
+    pheap_node_id_t id = add_alarm_under_lock(pool, time, callback, user_data, 0, true, &missed);
+    if (id) id_high = *get_entry_id_high(pool, id);
+    spin_unlock(pool->lock, save);
+    if (!id) return -1;
+    if (missed) {
+        // we want to fire the timer forcibly because it is in the past. Note that we do
+        // not care about racing with other timers, as it is harmless to have the IRQ
+        // wake up one time too many, we just need to make sure it does wake up
+        hardware_alarm_force_irq(pool->hardware_alarm_num);
+    }
+    return make_public_id(id_high, id);
+}
+
 bool alarm_pool_cancel_alarm(alarm_pool_t *pool, alarm_id_t alarm_id) {
     bool rc = false;
     uint32_t save = spin_lock_blocking(pool->lock);

src/host/hardware_timer/include/hardware/timer.h

@@ -31,10 +31,11 @@ bool time_reached(absolute_time_t t);
 typedef void (*hardware_alarm_callback_t)(uint alarm_num);
 void hardware_alarm_claim(uint alarm_num);
 void hardware_alarm_unclaim(uint alarm_num);
+int hardware_alarm_claim_unused(bool required);
 void hardware_alarm_set_callback(uint alarm_num, hardware_alarm_callback_t callback);
 bool hardware_alarm_set_target(uint alarm_num, absolute_time_t t);
 void hardware_alarm_cancel(uint alarm_num);
-
+void hardware_alarm_force_irq(uint alarm_num);
 #ifdef __cplusplus
 }
 #endif

src/host/hardware_timer/timer.c

@@ -87,6 +87,13 @@ void hardware_alarm_unclaim(uint alarm_num) {
     claimed_alarms &= ~(1u <<alarm_num);
 }
 
+int hardware_alarm_claim_unused(bool required) {
+    int alarm_id = claimed_alarms ? __builtin_clz(~claimed_alarms) : 1;
+    if (alarm_id >= NUM_TIMERS) return -1;
+    claimed_alarms |= 1u << alarm_id;
+    return alarm_id;
+}
+
 PICO_WEAK_FUNCTION_DEF(hardware_alarm_set_callback)
 void PICO_WEAK_FUNCTION_IMPL_NAME(hardware_alarm_set_callback)(uint alarm_num, hardware_alarm_callback_t callback) {
     panic_unsupported();
@@ -101,3 +108,8 @@ PICO_WEAK_FUNCTION_DEF(hardware_alarm_cancel)
 void PICO_WEAK_FUNCTION_IMPL_NAME(hardware_alarm_cancel)(uint alarm_num) {
     panic_unsupported();
 }
+
+PICO_WEAK_FUNCTION_DEF(hardware_alarm_force_irq)
+void PICO_WEAK_FUNCTION_IMPL_NAME(hardware_alarm_force_irq)(uint alarm_num) {
+    panic_unsupported();
+}

src/rp2040/hardware_regs/include/hardware/platform_defs.h

@@ -42,5 +42,7 @@
 #define XOSC_MHZ _u(12)
 #endif
 
+#define FIRST_USER_IRQ (NUM_IRQS - NUM_USER_IRQS)
+
 #endif
 

src/rp2_common/CMakeLists.txt

@@ -58,7 +58,8 @@ if (NOT PICO_BARE_METAL)
     pico_add_subdirectory(tinyusb)
     pico_add_subdirectory(pico_stdio_usb)
 
-    pico_add_subdirectory(cyw43_driver)
+    pico_add_subdirectory(pico_async_context)
+    pico_add_subdirectory(pico_cyw43_driver)
     pico_add_subdirectory(pico_lwip)
     pico_add_subdirectory(pico_cyw43_arch)
     pico_add_subdirectory(pico_mbedtls)

src/rp2_common/hardware_flash/include/hardware/flash.h

@@ -14,10 +14,11 @@
  *
  * Low level flash programming and erase API
  *
- * Note these functions are *unsafe* if you have two cores concurrently
+ * Note these functions are *unsafe* if you are using both cores, and the other 
- * executing from flash. In this case you must perform your own
+ * is executing from flash concurrently with the operation. In this could be the 
- * synchronisation to make sure no XIP accesses take place during flash
+ * case, you must perform your own synchronisation to make sure that no XIP
- * programming.
+ * accesses take place during flash programming. One option is to use the
+ * \ref multicore_lockout functions.
  *
  * Likewise they are *unsafe* if you have interrupt handlers or an interrupt
  * vector table in flash, so you must disable interrupts before calling in

src/rp2_common/hardware_irq/irq.c

@@ -435,8 +435,6 @@ void irq_init_priorities() {
 #endif
 }
 
-#define FIRST_USER_IRQ (NUM_IRQS - NUM_USER_IRQS)
-
 static uint get_user_irq_claim_index(uint irq_num) {
     invalid_params_if(IRQ, irq_num < FIRST_USER_IRQ || irq_num >= NUM_IRQS);
     // we count backwards from the last, to match the existing hard coded uses of user IRQs in the SDK which were previously using 31

src/rp2_common/hardware_timer/include/hardware/timer.h

@@ -136,6 +136,16 @@ typedef void (*hardware_alarm_callback_t)(uint alarm_num);
  */
 void hardware_alarm_claim(uint alarm_num);
 
+/*! \brief cooperatively claim the use of this hardware alarm_num
+ *  \ingroup hardware_timer
+ *
+ * This method attempts to claim an unused hardware alarm
+ *
+ * \return alarm_num the hardware alarm claimed or -1 if requires was false, and none are available
+ * \sa hardware_claiming
+ */
+int hardware_alarm_claim_unused(bool required);
+
 /*! \brief cooperatively release the claim on use of this hardware alarm_num
  *  \ingroup hardware_timer
  *
@@ -187,11 +197,23 @@ bool hardware_alarm_set_target(uint alarm_num, absolute_time_t t);
  * \brief Cancel an existing target (if any) for a given hardware_alarm
  * \ingroup hardware_timer
  *
- * @param alarm_num
+ * @param alarm_num the hardware alarm number
  */
-
 void hardware_alarm_cancel(uint alarm_num);
 
+/**
+ * \brief Force and IRQ for a specific hardware alarm
+ * \ingroup hardware_timer
+ *
+ * This method will forcibly make sure the current alarm callback (if present) for the hardware
+ * alarm is called from an IRQ context after this call. If an actual callback is due at the same
+ * time then the callback may only be called once.
+ *
+ * Calling this method does not otherwise interfere with regular callback operations.
+ *
+ * @param alarm_num the hardware alarm number
+ */
+void hardware_alarm_force_irq(uint alarm_num);
 #ifdef __cplusplus
 }
 #endif

src/rp2_common/hardware_timer/timer.c

@@ -33,6 +33,10 @@ bool hardware_alarm_is_claimed(uint alarm_num) {
     return hw_is_claimed(&claimed, alarm_num);
 }
 
+int hardware_alarm_claim_unused(bool required) {
+    return hw_claim_unused_from_range(&claimed, required, 0, NUM_TIMERS - 1, "No timers available");
+}
+
 /// tag::time_us_64[]
 uint64_t time_us_64() {
     // Need to make sure that the upper 32 bits of the timer
@@ -108,9 +112,7 @@ static inline uint harware_alarm_irq_number(uint alarm_num) {
 
 static void hardware_alarm_irq_handler(void) {
     // Determine which timer this IRQ is for
-    uint32_t ipsr;
+    uint alarm_num = __get_current_exception() - 16 - TIMER_IRQ_0;
-    __asm volatile ("mrs %0, ipsr" : "=r" (ipsr)::);
-    uint alarm_num = (ipsr & 0x3fu) - 16 - TIMER_IRQ_0;
     check_hardware_alarm_num_param(alarm_num);
 
     hardware_alarm_callback_t callback = NULL;
@@ -119,6 +121,8 @@ static void hardware_alarm_irq_handler(void) {
     uint32_t save = spin_lock_blocking(lock);
     // Clear the timer IRQ (inside lock, because we check whether we have handled the IRQ yet in alarm_set by looking at the interrupt status
     timer_hw->intr = 1u << alarm_num;
+    // Clear any forced IRQ
+    hw_clear_bits(&timer_hw->intf, 1u << alarm_num);
 
     // make sure the IRQ is still valid
     if (timer_callbacks_pending & (1u << alarm_num)) {
@@ -227,4 +231,11 @@ void hardware_alarm_cancel(uint alarm_num) {
     spin_unlock(lock, save);
 }
 
-
+void hardware_alarm_force_irq(uint alarm_num) {
+    check_hardware_alarm_num_param(alarm_num);
+    spin_lock_t *lock = spin_lock_instance(PICO_SPINLOCK_ID_TIMER);
+    uint32_t save = spin_lock_blocking(lock);
+    timer_callbacks_pending |= (uint8_t)(1u << alarm_num);
+    spin_unlock(lock, save);
+    hw_set_bits(&timer_hw->intf, 1u << alarm_num);
+}

src/rp2_common/pico_async_context/CMakeLists.txt

@@ -0,0 +1,24 @@
+add_library(pico_async_context_base INTERFACE)
+target_include_directories(pico_async_context_base INTERFACE ${CMAKE_CURRENT_LIST_DIR}/include)
+target_sources(pico_async_context_base INTERFACE
+        ${CMAKE_CURRENT_LIST_DIR}/async_context_base.c
+        )
+target_link_libraries(pico_async_context_base INTERFACE pico_platform)
+
+pico_add_impl_library(pico_async_context_poll INTERFACE)
+target_sources(pico_async_context_poll INTERFACE
+        ${CMAKE_CURRENT_LIST_DIR}/async_context_poll.c
+)
+target_link_libraries(pico_async_context_poll INTERFACE pico_async_context_base)
+
+pico_add_impl_library(pico_async_context_threadsafe_background INTERFACE)
+target_sources(pico_async_context_threadsafe_background INTERFACE
+        ${CMAKE_CURRENT_LIST_DIR}/async_context_threadsafe_background.c
+        )
+target_link_libraries(pico_async_context_threadsafe_background INTERFACE pico_async_context_base)
+
+pico_add_impl_library(pico_async_context_freertos INTERFACE)
+target_sources(pico_async_context_freertos INTERFACE
+        ${CMAKE_CURRENT_LIST_DIR}/async_context_freertos.c
+        )
+target_link_libraries(pico_async_context_freertos INTERFACE pico_async_context_base)

src/rp2_common/pico_async_context/async_context_base.c

@@ -0,0 +1,123 @@
+/*
+ * Copyright (c) 2022 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include "pico/async_context_base.h"
+
+bool async_context_base_add_at_time_worker(async_context_t *self, async_at_time_worker_t *worker) {
+    async_at_time_worker_t **prev = &self->at_time_list;
+    while (*prev) {
+        if (worker == *prev) {
+            return false;
+        }
+        prev = &(*prev)->next;
+    }
+    *prev = worker;
+    worker->next = NULL;
+    return true;
+}
+
+bool async_context_base_remove_at_time_worker(async_context_t *self, async_at_time_worker_t *worker) {
+    async_at_time_worker_t **prev = &self->at_time_list;
+    while (*prev) {
+        if (worker == *prev) {
+            *prev = worker->next;
+            return true;
+        }
+        prev = &(*prev)->next;
+    }
+    return false;
+}
+
+bool async_context_base_add_when_pending_worker(async_context_t *self, async_when_pending_worker_t *worker) {
+    async_when_pending_worker_t **prev = &self->when_pending_list;
+    while (*prev) {
+        if (worker == *prev) {
+            return false;
+        }
+        prev = &(*prev)->next;
+    }
+    *prev = worker;
+    worker->next = NULL;
+    return true;
+}
+
+bool async_context_base_remove_when_pending_worker(async_context_t *self, async_when_pending_worker_t *worker) {
+    async_when_pending_worker_t **prev = &self->when_pending_list;
+    while (*prev) {
+        if (worker == *prev) {
+            *prev = worker->next;
+            return true;
+        }
+        prev = &(*prev)->next;
+    }
+    return false;
+}
+
+async_at_time_worker_t *async_context_base_remove_ready_at_time_worker(async_context_t *self) {
+    async_at_time_worker_t **best_prev = NULL;
+    if (self->at_time_list) {
+        absolute_time_t earliest = get_absolute_time();
+        for (async_at_time_worker_t **prev = &self->at_time_list; *prev; prev = &(*prev)->next) {
+            if (absolute_time_diff_us((*prev)->next_time, earliest) >= 0) {
+                earliest = (*prev)->next_time;
+                assert(!is_at_the_end_of_time(earliest)); // should never be less than now
+                best_prev = prev;
+            }
+        }
+    }
+    async_at_time_worker_t *rc;
+    if (best_prev) {
+        rc = *best_prev;
+        *best_prev = rc->next;
+    } else {
+        rc = NULL;
+    }
+    return rc;
+}
+
+void async_context_base_refresh_next_timeout(async_context_t *self) {
+    absolute_time_t earliest = at_the_end_of_time;
+    for (async_at_time_worker_t *worker = self->at_time_list; worker; ) {
+        async_at_time_worker_t *next = worker->next;
+        if (absolute_time_diff_us(worker->next_time, earliest) > 0) {
+            earliest = worker->next_time;
+        }
+        worker = next;
+    }
+    self->next_time = earliest;
+}
+
+absolute_time_t async_context_base_execute_once(async_context_t *self) {
+    async_at_time_worker_t *at_time_worker;
+    while (NULL != (at_time_worker = async_context_base_remove_ready_at_time_worker(self))) {
+        at_time_worker->do_work(self, at_time_worker);
+    }
+    for(async_when_pending_worker_t *when_pending_worker = self->when_pending_list; when_pending_worker; when_pending_worker = when_pending_worker->next) {
+        if (when_pending_worker->work_pending) {
+            when_pending_worker->work_pending = false;
+            when_pending_worker->do_work(self, when_pending_worker);
+        }
+    }
+    async_context_base_refresh_next_timeout(self);
+    return self->next_time;
+}
+
+bool async_context_base_needs_servicing(async_context_t *self) {
+    absolute_time_t now = get_absolute_time();
+    if (self->at_time_list) {
+        for (async_at_time_worker_t *worker = self->at_time_list; worker; worker = worker->next) {
+            if (absolute_time_diff_us(worker->next_time, now) >= 0) {
+                return true;
+            }
+        }
+    }
+    for(async_when_pending_worker_t *when_pending_worker = self->when_pending_list; when_pending_worker; when_pending_worker = when_pending_worker->next) {
+        if (when_pending_worker->work_pending) {
+            return true;
+        }
+    }
+    return false;
+}

src/rp2_common/pico_async_context/async_context_freertos.c

@@ -0,0 +1,293 @@
+/*
+ * Copyright (c) 2022 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <string.h>
+#include "pico/async_context_freertos.h"
+#include "pico/async_context_base.h"
+#include "pico/sync.h"
+#include "hardware/irq.h"
+
+#include "semphr.h"
+
+#if configNUM_CORES > 1 && !defined(configUSE_CORE_AFFINITY)
+#error async_context_freertos requires configUSE_CORE_AFFINITY under SMP
+#endif
+
+static const async_context_type_t template;
+
+static void async_context_freertos_acquire_lock_blocking(async_context_t *self_base);
+static void async_context_freertos_release_lock(async_context_t *self_base);
+static void async_context_freertos_lock_check(async_context_t *self_base);
+
+static TickType_t sensible_ticks_until(absolute_time_t until) {
+    TickType_t ticks;
+    int64_t delay_us = absolute_time_diff_us(get_absolute_time(), until);
+    if (delay_us <= 0) {
+        ticks = 0;
+    } else {
+        static const uint32_t max_delay = 60000000;
+        uint32_t delay_us_32 = delay_us > max_delay ? max_delay : (uint32_t) delay_us;
+        ticks = pdMS_TO_TICKS((delay_us_32+999)/1000);
+        // we want to round up, as both rounding down to zero is wrong (may produce no delays
+        // where delays are needed), but also we don't want to wake up, and then realize there
+        // is no work to do yet!
+        ticks++;
+    }
+    return ticks;
+}
+
+static void process_under_lock(async_context_freertos_t *self) {
+#ifndef NDEBUG
+    async_context_freertos_lock_check(&self->core);
+#endif
+    bool repeat;
+    do {
+        repeat = false;
+        absolute_time_t next_time = async_context_base_execute_once(&self->core);
+        TickType_t ticks;
+        if (is_at_the_end_of_time(next_time)) {
+            ticks = portMAX_DELAY;
+        } else {
+            ticks = sensible_ticks_until(next_time);
+        }
+        if (ticks) {
+            // last parameter (timeout) is also 'ticks', since there is no point waiting to change the period
+            // for longer than the period itself!
+            repeat = pdFALSE == xTimerChangePeriod(self->timer_handle, ticks, ticks);
+        } else {
+            repeat = true;
+        }
+    } while (repeat);
+}
+
+static void async_context_task(__unused void *vself) {
+    async_context_freertos_t *self = (async_context_freertos_t *)vself;
+    do {
+        ulTaskNotifyTake(pdFALSE, portMAX_DELAY);
+        if (self->task_should_exit) break;
+        async_context_freertos_acquire_lock_blocking(&self->core);
+        process_under_lock(self);
+        async_context_freertos_release_lock(&self->core);
+        __sev(); // it is possible regular code is waiting on a WFE on the other core
+    } while (!self->task_should_exit);
+    vTaskDelete(NULL);
+}
+
+static void async_context_freertos_wake_up(async_context_t *self_base) {
+    async_context_freertos_t *self = (async_context_freertos_t *)self_base;
+    if (self->task_handle) {
+        if (portCHECK_IF_IN_ISR()) {
+            vTaskNotifyGiveFromISR(self->task_handle, NULL);
+            xSemaphoreGiveFromISR(self->work_needed_sem, NULL);
+        } else {
+            // we don't want to wake ourselves up (we will only ever be called
+            // from the async_context_task if we own the lock, in which case processing
+            // will already happen when the lock is finally unlocked
+            if (xTaskGetCurrentTaskHandle() != self->task_handle) {
+                xTaskNotifyGive(self->task_handle);
+                xSemaphoreGive(self->work_needed_sem);
+            } else {
+#ifndef NDEBUG
+                async_context_freertos_lock_check(self_base);
+#endif
+            }
+        }
+    }
+}
+
+static void timer_handler(__unused TimerHandle_t handle)
+{
+    async_context_freertos_t *self = (async_context_freertos_t *)pvTimerGetTimerID(handle);
+    async_context_freertos_wake_up(&self->core);
+}
+
+bool async_context_freertos_init(async_context_freertos_t *self, async_context_freertos_config_t *config) {
+    memset(self, 0, sizeof(*self));
+    self->core.type = &template;
+    self->core.flags = ASYNC_CONTEXT_FLAG_CALLBACK_FROM_NON_IRQ;
+    self->core.core_num = get_core_num();
+    self->lock_mutex = xSemaphoreCreateRecursiveMutex();
+    self->work_needed_sem = xSemaphoreCreateBinary();
+    self->timer_handle = xTimerCreate( "async_context_timer",       // Just a text name, not used by the kernel.
+                                    portMAX_DELAY,
+                                    pdFALSE,        // The timers will auto-reload themselves when they expire.
+                                    self,
+                                    timer_handler);
+
+    if (!self->lock_mutex ||
+        !self->work_needed_sem ||
+        !self->timer_handle ||
+        pdPASS != xTaskCreate(async_context_task, "async_context_task", config->task_stack_size, self,
+                config->task_priority, &self->task_handle)) {
+        async_context_deinit(&self->core);
+        return false;
+    }
+#if configNUM_CORES > 1
+    UBaseType_t core_id = config->task_core_id;
+    if (core_id == (UBaseType_t)-1) {
+        core_id = portGET_CORE_ID();
+    }
+    // we must run on a single core
+    vTaskCoreAffinitySet(self->task_handle, 1u << core_id);
+#endif
+    return true;
+}
+
+static uint32_t end_task_func(void *param) {
+    async_context_freertos_t *self = (async_context_freertos_t *)param;
+    // we will immediately exit
+    self->task_should_exit = true;
+    return 0;
+}
+
+void async_context_freertos_deinit(async_context_t *self_base) {
+    async_context_freertos_t *self = (async_context_freertos_t *)self_base;
+    if (self->task_handle) {
+        async_context_execute_sync(self_base, end_task_func, self_base);
+    }
+    if (self->timer_handle) {
+        xTimerDelete(self->timer_handle, 0);
+    }
+    if (self->lock_mutex) {
+        vSemaphoreDelete(self->lock_mutex);
+    }
+    if (self->work_needed_sem) {
+        vSemaphoreDelete(self->work_needed_sem);
+    }
+    memset(self, 0, sizeof(*self));
+}
+
+void async_context_freertos_acquire_lock_blocking(async_context_t *self_base) {
+    async_context_freertos_t *self = (async_context_freertos_t *)self_base;
+    // Lock the other core and stop low_prio_irq running
+    assert(!portCHECK_IF_IN_ISR());
+    xSemaphoreTakeRecursive(self->lock_mutex, portMAX_DELAY);
+    self->nesting++;
+}
+
+void async_context_freertos_lock_check(async_context_t *self_base) {
+    async_context_freertos_t *self = (async_context_freertos_t *)self_base;
+    // Lock the other core and stop low_prio_irq running
+    assert(xSemaphoreGetMutexHolder(self->lock_mutex) == xTaskGetCurrentTaskHandle());
+}
+
+typedef struct sync_func_call{
+    async_when_pending_worker_t worker;
+    SemaphoreHandle_t sem;
+    uint32_t (*func)(void *param);
+    void *param;
+    uint32_t rc;
+} sync_func_call_t;
+
+static void handle_sync_func_call(async_context_t *context, async_when_pending_worker_t *worker) {
+    sync_func_call_t *call = (sync_func_call_t *)worker;
+    call->rc = call->func(call->param);
+    xSemaphoreGive(call->sem);
+    async_context_remove_when_pending_worker(context, worker);
+}
+
+uint32_t async_context_freertos_execute_sync(async_context_t *self_base, uint32_t (*func)(void *param), void *param) {
+    async_context_freertos_t *self = (async_context_freertos_t*)self_base;
+    hard_assert(xSemaphoreGetMutexHolder(self->lock_mutex) != xTaskGetCurrentTaskHandle());
+    sync_func_call_t call;
+    call.worker.do_work = handle_sync_func_call;
+    call.func = func;
+    call.param = param;
+    call.sem = xSemaphoreCreateBinary();
+    async_context_add_when_pending_worker(self_base, &call.worker);
+    async_context_set_work_pending(self_base, &call.worker);
+    xSemaphoreTake(call.sem, portMAX_DELAY);
+    vSemaphoreDelete(call.sem);
+    return call.rc;
+}
+
+void async_context_freertos_release_lock(async_context_t *self_base) {
+    async_context_freertos_t *self = (async_context_freertos_t *)self_base;
+    bool do_wakeup = false;
+    if (self->nesting == 1) {
+        // note that we always do a processing on outermost lock exit, to facilitate cases
+        // like lwIP where we have no notification when lwIP timers are added.
+        //
+        // this operation must be done from the right task
+        if (self->task_handle != xTaskGetCurrentTaskHandle()) {
+            // note we defer the wakeup until after we release the lock, otherwise it can be wasteful
+            // (waking up the task, but then having it block immediately on us)
+            do_wakeup = true;
+        } else {
+            process_under_lock(self);
+        }
+    }
+    --self->nesting;
+    xSemaphoreGiveRecursive(self->lock_mutex);
+    if (do_wakeup) {
+        async_context_freertos_wake_up(self_base);
+    }
+}
+
+static bool async_context_freertos_add_at_time_worker(async_context_t *self_base, async_at_time_worker_t *worker) {
+    async_context_freertos_acquire_lock_blocking(self_base);
+    bool rc = async_context_base_add_at_time_worker(self_base, worker);
+    async_context_freertos_release_lock(self_base);
+    return rc;
+}
+
+static bool async_context_freertos_remove_at_time_worker(async_context_t *self_base, async_at_time_worker_t *worker) {
+    async_context_freertos_acquire_lock_blocking(self_base);
+    bool rc = async_context_base_remove_at_time_worker(self_base, worker);
+    async_context_freertos_release_lock(self_base);
+    return rc;
+}
+
+static bool async_context_freertos_add_when_pending_worker(async_context_t *self_base, async_when_pending_worker_t *worker) {
+    async_context_freertos_acquire_lock_blocking(self_base);
+    bool rc = async_context_base_add_when_pending_worker(self_base, worker);
+    async_context_freertos_release_lock(self_base);
+    return rc;
+}
+
+static bool async_context_freertos_remove_when_pending_worker(async_context_t *self_base, async_when_pending_worker_t *worker) {
+    async_context_freertos_acquire_lock_blocking(self_base);
+    bool rc = async_context_base_remove_when_pending_worker(self_base, worker);
+    async_context_freertos_release_lock(self_base);
+    return rc;
+}
+
+static void async_context_freertos_set_work_pending(async_context_t *self_base, async_when_pending_worker_t *worker) {
+    worker->work_pending = true;
+    async_context_freertos_wake_up(self_base);
+}
+
+static void async_context_freertos_wait_until(async_context_t *self_base, absolute_time_t until) {
+    assert(!portCHECK_IF_IN_ISR());
+    TickType_t ticks = sensible_ticks_until(until);
+    vTaskDelay(ticks);
+}
+
+static void async_context_freertos_wait_for_work_until(async_context_t *self_base, absolute_time_t until) {
+    async_context_freertos_t *self = (async_context_freertos_t *)self_base;
+    assert(!portCHECK_IF_IN_ISR());
+    while (!time_reached(until)) {
+        TickType_t ticks = sensible_ticks_until(until);
+        if (!ticks || xSemaphoreTake(self->work_needed_sem, ticks)) return;
+    }
+}
+
+static const async_context_type_t template = {
+        .type = ASYNC_CONTEXT_FREERTOS,
+        .acquire_lock_blocking = async_context_freertos_acquire_lock_blocking,
+        .release_lock = async_context_freertos_release_lock,
+        .lock_check = async_context_freertos_lock_check,
+        .execute_sync = async_context_freertos_execute_sync,
+        .add_at_time_worker = async_context_freertos_add_at_time_worker,
+        .remove_at_time_worker = async_context_freertos_remove_at_time_worker,
+        .add_when_pending_worker = async_context_freertos_add_when_pending_worker,
+        .remove_when_pending_worker = async_context_freertos_remove_when_pending_worker,
+        .set_work_pending = async_context_freertos_set_work_pending,
+        .poll = 0,
+        .wait_until = async_context_freertos_wait_until,
+        .wait_for_work_until = async_context_freertos_wait_for_work_until,
+        .deinit = async_context_freertos_deinit,
+};

src/rp2_common/pico_async_context/async_context_poll.c

@@ -0,0 +1,73 @@
+/*
+ * Copyright (c) 2022 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <string.h>
+#include "pico/async_context_poll.h"
+#include "pico/async_context_base.h"
+#include "pico/sync.h"
+
+static void noop(__unused async_context_t *context) { }
+
+static const async_context_type_t template;
+
+bool async_context_poll_init_with_defaults(async_context_poll_t *self) {
+    memset(self, 0, sizeof(*self));
+    self->core.core_num = get_core_num();
+    self->core.type = &template;
+    self->core.flags = ASYNC_CONTEXT_FLAG_POLLED | ASYNC_CONTEXT_FLAG_CALLBACK_FROM_NON_IRQ;
+    sem_init(&self->sem, 1, 1);
+    return true;
+}
+
+static void async_context_poll_wake_up(async_context_t *self_base) {
+    sem_release(&((async_context_poll_t *)self_base)->sem);
+}
+
+static void async_context_poll_requires_update(async_context_t *self_base, async_when_pending_worker_t *worker) {
+    worker->work_pending = true;
+    async_context_poll_wake_up(self_base);
+}
+
+static void async_context_poll_poll(async_context_t *self_base) {
+    async_context_base_execute_once(self_base);
+}
+
+static void async_context_poll_wait_until(__unused async_context_t *self_base, absolute_time_t until) {
+    sleep_until(until);
+}
+
+static void async_context_poll_wait_for_work_until(async_context_t *self_base, absolute_time_t until) {
+    absolute_time_t next_time = self_base->next_time;
+    async_context_poll_t *self = (async_context_poll_t *)self_base;
+    sem_acquire_block_until(&self->sem, absolute_time_min(next_time, until));
+}
+
+static void async_context_poll_lock_check(async_context_t *self_base) {
+    if (__get_current_exception() || get_core_num() != self_base->core_num) {
+        panic("async_context_poll context check failed (IRQ or wrong core)");
+    }
+}
+
+uint32_t async_context_poll_execute_sync(__unused async_context_t *context, uint32_t (*func)(void *param), void *param) {
+    return func(param);
+}
+
+static const async_context_type_t template = {
+        .type = ASYNC_CONTEXT_POLL,
+        .acquire_lock_blocking = noop,
+        .release_lock = noop,
+        .lock_check = async_context_poll_lock_check,
+        .execute_sync = async_context_poll_execute_sync,
+        .add_at_time_worker = async_context_base_add_at_time_worker,
+        .remove_at_time_worker = async_context_base_remove_at_time_worker,
+        .add_when_pending_worker = async_context_base_add_when_pending_worker,
+        .remove_when_pending_worker = async_context_base_remove_when_pending_worker,
+        .set_work_pending = async_context_poll_requires_update,
+        .poll = async_context_poll_poll,
+        .wait_until = async_context_poll_wait_until,
+        .wait_for_work_until = async_context_poll_wait_for_work_until,
+        .deinit = noop,
+};

src/rp2_common/pico_async_context/async_context_threadsafe_background.c

@@ -0,0 +1,369 @@
+/*
+ * Copyright (c) 2022 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <string.h>
+#include "pico/async_context_threadsafe_background.h"
+#include "pico/async_context_base.h"
+#include "pico/sync.h"
+#include "hardware/irq.h"
+
+static const async_context_type_t template;
+static async_context_threadsafe_background_t *async_contexts_by_user_irq[NUM_USER_IRQS];
+
+static void low_priority_irq_handler(void);
+static void process_under_lock(async_context_threadsafe_background_t *self);
+static int64_t alarm_handler(alarm_id_t id, void *user_data);
+
+#ifndef ASYNC_CONTEXT_THREADSAFE_BACKGROUND_DEFAULT_LOW_PRIORITY_IRQ_HANDLER_PRIORITY
+#define ASYNC_CONTEXT_THREADSAFE_BACKGROUND_DEFAULT_LOW_PRIORITY_IRQ_HANDLER_PRIORITY PICO_LOWEST_IRQ_PRIORITY
+#endif
+
+#ifndef ASYNC_CONTEXT_THREADSAFE_BACKGROUND_ALARM_POOL_MAX_ALARMS
+#define ASYNC_CONTEXT_THREADSAFE_BACKGROUND_ALARM_POOL_MAX_ALARMS 4
+#endif
+
+async_context_threadsafe_background_config_t async_context_threadsafe_background_default_config(void) {
+    async_context_threadsafe_background_config_t config = {
+            .low_priority_irq_handler_priority = ASYNC_CONTEXT_THREADSAFE_BACKGROUND_DEFAULT_LOW_PRIORITY_IRQ_HANDLER_PRIORITY,
+            .custom_alarm_pool = NULL,
+    };
+    return config;
+}
+
+static inline uint recursive_mutex_enter_count(recursive_mutex_t *mutex) {
+    return mutex->enter_count;
+}
+
+static inline lock_owner_id_t recursive_mutex_owner(recursive_mutex_t *mutex) {
+    return mutex->owner;
+}
+
+static void async_context_threadsafe_background_wake_up(async_context_t *self_base) {
+    async_context_threadsafe_background_t *self = (async_context_threadsafe_background_t *)self_base;
+#if ASYNC_CONTEXT_THREADSAFE_BACKGROUND_MULTI_CORE
+    if (self_base->core_num == get_core_num()) {
+        // on same core, can dispatch directly
+        irq_set_pending(self->low_priority_irq_num);
+    } else {
+        // remove the existing alarm (it may have already fired) so we don't overflow the pool with repeats
+        //
+        // note that force_alarm_id is not protected here, however if we miss removing one, they will fire
+        // almost immediately anyway (since they were set in the past)
+        alarm_id_t force_alarm_id = self->force_alarm_id;
+        if (force_alarm_id > 0) {
+            alarm_pool_cancel_alarm(self->alarm_pool, force_alarm_id);
+        }
+        // we cause an early timeout (0 is always in the past) on the alarm_pool core
+        // note that by the time this returns, the timer may already have fired, so we
+        // may end up setting self->force_alarm_id to a stale timer id, but that is fine as we
+        // will harmlessly cancel it again next time
+        self->force_alarm_id = alarm_pool_add_alarm_at_force_in_context(self->alarm_pool, from_us_since_boot(0),
+                                                                        alarm_handler, self);
+    }
+#else
+    // on same core, can dispatch directly
+    irq_set_pending(self->low_priority_irq_num);
+#endif
+    sem_release(&self->work_needed_sem);
+}
+
+// Prevent background processing in pensv and access by the other core
+// These methods are called in pensv context and on either core
+// They can be called recursively
+static inline void lock_acquire(async_context_threadsafe_background_t *self) {
+    // Lock the other core and stop low_prio_irq running
+    recursive_mutex_enter_blocking(&self->lock_mutex);
+}
+
+static void async_context_threadsafe_background_lock_check(async_context_t *self_base) {
+    async_context_threadsafe_background_t *self = (async_context_threadsafe_background_t *)self_base;
+    // Lock the other core and stop low_prio_irq running
+    if (recursive_mutex_enter_count(&self->lock_mutex) < 1 || recursive_mutex_owner(&self->lock_mutex) != lock_get_caller_owner_id()) {
+        panic_compact("async_context lock_check failed");
+    }
+}
+
+typedef struct sync_func_call{
+    async_when_pending_worker_t worker;
+    semaphore_t sem;
+    uint32_t (*func)(void *param);
+    void *param;
+    uint32_t rc;
+} sync_func_call_t;
+
+static void handle_sync_func_call(async_context_t *context, async_when_pending_worker_t *worker) {
+    sync_func_call_t *call = (sync_func_call_t *)worker;
+    call->rc = call->func(call->param);
+    sem_release(&call->sem);
+    async_context_remove_when_pending_worker(context, worker);
+}
+
+
+static void lock_release(async_context_threadsafe_background_t *self) {
+    bool outermost = 1 == recursive_mutex_enter_count(&self->lock_mutex);
+    // note that it is *not* a requirement to have low_prio_irq_missed handled on the
+    // same core and in low-priority riq, as we are only *logically* a single thread. the user
+    // is already free to call from either core, and this would only happen on a different
+    // core, if the user *themselves* is acquiring the lock from other cores anyway
+
+#if ASYNC_CONTEXT_THREADSAFE_BACKGROUND_MULTI_CORE
+    bool wake_other_core = false;
+#endif
+    if (outermost) {
+        // note that we always do a processing on outermost lock exit, to facilitate cases
+        // like lwIP where we have no notification when lwIP timers are added.
+#if ASYNC_CONTEXT_THREADSAFE_BACKGROUND_MULTI_CORE
+        if (self->core.core_num == get_core_num()) {
+            process_under_lock(self);
+        } else if (async_context_base_needs_servicing(&self->core)) {
+            // have to wake up other core
+            wake_other_core = true;
+        }
+#else
+        process_under_lock(self);
+#endif
+    }
+    recursive_mutex_exit(&self->lock_mutex);
+#if ASYNC_CONTEXT_THREADSAFE_BACKGROUND_MULTI_CORE
+    if (wake_other_core) {
+        async_context_threadsafe_background_wake_up(&self->core);
+    }
+#endif
+}
+
+uint32_t async_context_threadsafe_background_execute_sync(async_context_t *self_base, uint32_t (*func)(void *param), void *param) {
+    async_context_threadsafe_background_t *self = (async_context_threadsafe_background_t*)self_base;
+#if ASYNC_CONTEXT_THREADSAFE_BACKGROUND_MULTI_CORE
+    if (self_base->core_num != get_core_num()) {
+        hard_assert(!recursive_mutex_enter_count(&self->lock_mutex));
+        sync_func_call_t call;
+        call.worker.do_work = handle_sync_func_call;
+        call.func = func;
+        call.param = param;
+        sem_init(&call.sem, 0, 1);
+        async_context_add_when_pending_worker(self_base, &call.worker);
+        async_context_set_work_pending(self_base, &call.worker);
+        sem_acquire_blocking(&call.sem);
+        return call.rc;
+    }
+#endif
+    // short-circuit if we are on the right core
+    lock_acquire(self);
+    uint32_t rc = func(param);
+    lock_release(self);
+    return rc;
+}
+
+static bool low_prio_irq_init(async_context_threadsafe_background_t  *self, uint8_t priority) {
+    assert(get_core_num() == self->core.core_num);
+    int irq = user_irq_claim_unused(false);
+    if (irq < 0) return false;
+    self->low_priority_irq_num = (uint8_t) irq;
+    uint index = irq - FIRST_USER_IRQ;
+    assert(index < count_of(async_contexts_by_user_irq));
+    async_contexts_by_user_irq[index] = self;
+    irq_set_exclusive_handler(self->low_priority_irq_num, low_priority_irq_handler);
+    irq_set_enabled(self->low_priority_irq_num, true);
+    irq_set_priority(self->low_priority_irq_num, priority);
+    return true;
+}
+
+static void low_prio_irq_deinit(async_context_threadsafe_background_t *self) {
+    if (self->low_priority_irq_num > 0) {
+        assert(get_core_num() == self->core.core_num);
+        irq_set_enabled(self->low_priority_irq_num, false);
+        irq_remove_handler(self->low_priority_irq_num, low_priority_irq_handler);
+        user_irq_unclaim(self->low_priority_irq_num);
+        self->low_priority_irq_num = 0;
+    }
+}
+
+static int64_t alarm_handler(__unused alarm_id_t id, void *user_data) {
+    async_context_threadsafe_background_t *self = (async_context_threadsafe_background_t*)user_data;
+#if ASYNC_CONTEXT_THREADSAFE_BACKGROUND_MULTI_CORE
+    self->force_alarm_id = 0;
+#endif
+    self->alarm_pending = false;
+    async_context_threadsafe_background_wake_up(&self->core);
+    return 0;
+}
+
+bool async_context_threadsafe_background_init(async_context_threadsafe_background_t *self, async_context_threadsafe_background_config_t *config) {
+    memset(self, 0, sizeof(*self));
+    self->core.type = &template;
+    self->core.flags = ASYNC_CONTEXT_FLAG_CALLBACK_FROM_IRQ | ASYNC_CONTEXT_FLAG_CALLBACK_FROM_NON_IRQ;
+    self->core.core_num = get_core_num();
+    if (config->custom_alarm_pool) {
+        self->alarm_pool = config->custom_alarm_pool;
+    } else {
+#if PICO_TIME_DEFAULT_ALARM_POOL_DISABLED
+        self->alarm_pool = alarm_pool_create_with_unused_hardware_alarm(ASYNC_CONTEXT_THREADSAFE_BACKGROUND_ALARM_POOL_MAX_ALARMS);
+        self->alarm_pool_owned = true;
+#else
+        self->alarm_pool = alarm_pool_get_default();
+#if ASYNC_CONTEXT_THREADSAFE_BACKGROUND_MULTI_CORE
+        if (self->core.core_num != alarm_pool_core_num(self->alarm_pool)) {
+            self->alarm_pool = alarm_pool_create_with_unused_hardware_alarm(ASYNC_CONTEXT_THREADSAFE_BACKGROUND_ALARM_POOL_MAX_ALARMS);
+            self->alarm_pool_owned = true;
+        }
+#endif
+#endif
+    }
+    assert(self->core.core_num == alarm_pool_core_num(self->alarm_pool));
+    sem_init(&self->work_needed_sem, 1, 1);
+    recursive_mutex_init(&self->lock_mutex);
+    bool ok = low_prio_irq_init(self, config->low_priority_irq_handler_priority);
+    return ok;
+}
+
+static void async_context_threadsafe_background_set_work_pending(async_context_t *self_base, async_when_pending_worker_t *worker) {
+    worker->work_pending = true;
+    async_context_threadsafe_background_wake_up(self_base);
+}
+
+static void async_context_threadsafe_background_deinit(async_context_t *self_base) {
+    async_context_threadsafe_background_t *self = (async_context_threadsafe_background_t *)self_base;
+    // todo we do not currently handle this correctly; we could, but seems like a rare case
+    assert(get_core_num() == self_base->core_num);
+    low_prio_irq_deinit(self);
+    if (self->alarm_id > 0) alarm_pool_cancel_alarm(self->alarm_pool, self->alarm_id);
+#if ASYNC_CONTEXT_THREADSAFE_BACKGROUND_MULTI_CORE
+    if (self->alarm_pool_owned) {
+        alarm_pool_destroy(self->alarm_pool);
+    }
+#endif
+    // acquire the lock to make sure the callback is not running (we have already disabled the IRQ
+    recursive_mutex_enter_blocking(&self->lock_mutex);
+    recursive_mutex_exit(&self->lock_mutex);
+    memset(self, 0, sizeof(*self));
+}
+
+static void process_under_lock(async_context_threadsafe_background_t *self) {
+#ifndef NDEBUG
+    async_context_threadsafe_background_lock_check(&self->core);
+    assert(self->core.core_num == get_core_num());
+#endif
+    do {
+        absolute_time_t next_time = async_context_base_execute_once(&self->core);
+        // if the next wakeup time is in the past then loop
+        if (absolute_time_diff_us(get_absolute_time(), next_time) <= 0) continue;
+        // if there is no next wakeup time, we're done
+        if (is_at_the_end_of_time(next_time)) {
+            // cancel the alarm early (we will have been called soon after an alarm wakeup), so that
+            // we don't risk alarm_id collision.
+            if (self->alarm_id > 0) {
+                alarm_pool_cancel_alarm(self->alarm_pool, self->alarm_id);
+                self->alarm_id = 0;
+            }
+            break;
+        }
+        // the following is an optimization; we are often called much more frequently than timeouts actually change,
+        // and removing and re-adding the timers has some non-trivial overhead (10s of microseconds), we choose
+        // to allow the existing timeout to run to completion, and then re-asses from there, unless the new wakeup
+        // time is before the last one set.
+        //
+        // note that alarm_pending is not protected, however, if it is wrong, it is wrong in the sense that it is
+        // false when it should be true, so if it is wrong due to a race, we will cancel and re-add the alarm which is safe.
+        if (self->alarm_pending && absolute_time_diff_us(self->last_set_alarm_time, next_time) > 0) break;
+        // cancel the existing alarm (it may no longer exist)
+        if (self->alarm_id > 0) alarm_pool_cancel_alarm(self->alarm_pool, self->alarm_id);
+        self->last_set_alarm_time = next_time;
+        self->alarm_pending = true;
+        self->alarm_id = alarm_pool_add_alarm_at(self->alarm_pool, next_time, alarm_handler, self, false);
+        if (self->alarm_id > 0) break;
+        self->alarm_pending = false;
+    } while (true);
+}
+
+// Low priority interrupt handler to perform background processing
+static void low_priority_irq_handler(void) {
+    uint index = __get_current_exception() - 16 - FIRST_USER_IRQ;
+    assert(index < count_of(async_contexts_by_user_irq));
+    async_context_threadsafe_background_t *self = async_contexts_by_user_irq[index];
+    if (!self) return;
+    assert(self->core.core_num == get_core_num());
+    if (recursive_mutex_try_enter(&self->lock_mutex, NULL)) {
+        // if the recurse count is not 1 then we have pre-empted something which held the lock on the same core,
+        // so we cannot do processing here (however processing will be done when that lock is released)
+        if (recursive_mutex_enter_count(&self->lock_mutex) == 1) {
+            process_under_lock(self);
+        }
+        recursive_mutex_exit(&self->lock_mutex);
+    }
+}
+
+static void async_context_threadsafe_background_wait_until(__unused async_context_t *self_base, absolute_time_t until) {
+    // can be called in IRQs, in which case we just have to wait
+    if (__get_current_exception()) {
+        busy_wait_until(until);
+    } else {
+        sleep_until(until);
+    }
+}
+
+static void async_context_threadsafe_background_wait_for_work_until(async_context_t *self_base, absolute_time_t until) {
+    async_context_threadsafe_background_t *self = (async_context_threadsafe_background_t *)self_base;
+    sem_acquire_block_until(&self->work_needed_sem, until);
+}
+
+static bool async_context_threadsafe_background_add_at_time_worker(async_context_t *self_base, async_at_time_worker_t *worker) {
+    async_context_threadsafe_background_t *self = (async_context_threadsafe_background_t *)self_base;
+    lock_acquire(self);
+    bool rc = async_context_base_add_at_time_worker(self_base, worker);
+    lock_release(self);
+    return rc;
+}
+
+static bool async_context_threadsafe_background_remove_at_time_worker(async_context_t *self_base, async_at_time_worker_t *worker) {
+    async_context_threadsafe_background_t *self = (async_context_threadsafe_background_t *)self_base;
+    lock_acquire(self);
+    bool rc = async_context_base_remove_at_time_worker(self_base, worker);
+    lock_release(self);
+    return rc;
+}
+
+static bool async_context_threadsafe_background_add_when_pending_worker(async_context_t *self_base, async_when_pending_worker_t *worker) {
+    async_context_threadsafe_background_t *self = (async_context_threadsafe_background_t *)self_base;
+    lock_acquire(self);
+    bool rc = async_context_base_add_when_pending_worker(self_base, worker);
+    lock_release(self);
+    return rc;
+}
+
+static bool async_context_threadsafe_background_when_pending_worker(async_context_t *self_base, async_when_pending_worker_t *worker) {
+    async_context_threadsafe_background_t *self = (async_context_threadsafe_background_t *)self_base;
+    lock_acquire(self);
+    bool rc = async_context_base_remove_when_pending_worker(self_base, worker);
+    lock_release(self);
+    return rc;
+}
+
+static void async_context_threadsafe_background_acquire_lock_blocking(async_context_t *self_base) {
+    lock_acquire((async_context_threadsafe_background_t *) self_base);
+}
+
+static void async_context_threadsafe_background_release_lock(async_context_t *self_base) {
+    lock_release((async_context_threadsafe_background_t *)self_base);
+}
+
+static const async_context_type_t template = {
+        .type = ASYNC_CONTEXT_THREADSAFE_BACKGROUND,
+        .acquire_lock_blocking = async_context_threadsafe_background_acquire_lock_blocking,
+        .release_lock = async_context_threadsafe_background_release_lock,
+        .lock_check = async_context_threadsafe_background_lock_check,
+        .execute_sync = async_context_threadsafe_background_execute_sync,
+        .add_at_time_worker = async_context_threadsafe_background_add_at_time_worker,
+        .remove_at_time_worker = async_context_threadsafe_background_remove_at_time_worker,
+        .add_when_pending_worker = async_context_threadsafe_background_add_when_pending_worker,
+        .remove_when_pending_worker = async_context_threadsafe_background_when_pending_worker,
+        .set_work_pending = async_context_threadsafe_background_set_work_pending,
+        .poll = 0,
+        .wait_until = async_context_threadsafe_background_wait_until,
+        .wait_for_work_until = async_context_threadsafe_background_wait_for_work_until,
+        .deinit = async_context_threadsafe_background_deinit,
+};
+
+

src/rp2_common/pico_async_context/include/pico/async_context.h

@@ -0,0 +1,462 @@
+/*
+ * Copyright (c) 2022 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+/** \file pico/async_context.h
+ *  \defgroup pico_async_context pico_async_context
+ *
+ * An \ref async_context provides a logically single-threaded context for performing work, and responding
+ * to asynchronous events. Thus an async_context instance is suitable for servicing third-party libraries
+ * that are not re-entrant.
+ *
+ * The "context" in async_context refers to the fact that when calling workers or timeouts within the
+ * async_context various pre-conditions hold:
+ *
+ * <ol>
+ * <li>That there is a single logical thread of execution; i.e. that the context does not call any worker
+ * functions concurrently.
+ * <li>That the context always calls workers from the same processor core, as most uses of async_context rely on interaction
+ * with IRQs which are themselves core-specific.
+ * </ol>
+ *
+ * THe async_context provides two mechanisms for asynchronous work:
+ *
+ * * <em>when_pending</em> workers, which are processed whenever they have work pending. See \ref async_context_add_when_pending_worker,
+ * \ref async_context_remove_when_pending_worker, and \ref async_context_set_work_pending, the latter of which can be used from an interrupt handler
+ * to signal that servicing work is required to be performed by the worker from the regular async_context.
+ * * <em>at_time</em> workers, that are executed after at a specific time.
+ *
+ * Note: "when pending" workers with work pending are executed before "at time" workers.
+ *
+ * The async_context provides locking mechanisms, see \ref async_context_acquire_lock_blocking,
+ * \ref async_context_release_lock and \ref async_context_check_lock which can be used by
+ * external code to ensure execution of external code does not happen concurrently with worker code.
+ * Locked code runs on the calling core, however \ref async_context_execute_sync is provided to
+ * synchronously run a function from the core of the async_context.
+ *
+ * The SDK ships with the following default async_contexts:
+ *
+ * async_context_poll - this context is not thread-safe, and the user is responsible for calling
+ * \ref async_context_poll() periodically, and can use async_context_wait_for_work_until() to sleep
+ * between calls until work is needed if the user has nothing else to do.
+ *
+ * async_context_threadsafe_background - in order to work in the background, a low priority IRQ is used
+ * to handle callbacks. Code is usually invoked from this IRQ context, but may be invoked after any other code
+ * that uses the async context in another (non-IRQ) context on the same core. Calling \ref async_context_poll() is
+ * not required, and is a no-op. This context implements async_context locking and is thus safe to call
+ * from either core, according to the specific notes on each API.
+ *
+ * async_context_freertos - Work is performed from a separate "async_context" task, however once again, code may
+ * also be invoked after a direct use of the async_context on the same core that the async_context belongs to. Calling
+ * \ref async_context_poll() is not required, and is a no-op. This context implements async_context locking and is thus
+ * safe to call from any task, and from either core, according to the specific notes on each API.
+ *
+ * Each async_context provides bespoke methods of instantiation which are provided in the corresponding headers (e.g.
+ * async_context_poll.h, async_context_threadsafe_background.h, asycn_context_freertos.h).
+ * async_contexts are de-initialized by the common async_context_deint() method.
+ *
+ * Multiple async_context instances can be used by a single application, and they will operate independently.
+ */
+
+#ifndef _PICO_ASYNC_CONTEXT_H
+#define _PICO_ASYNC_CONTEXT_H
+
+#include "pico.h"
+#include "pico/time.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+enum {
+    ASYNC_CONTEXT_POLL = 1,
+    ASYNC_CONTEXT_THREADSAFE_BACKGROUND = 2,
+    ASYNC_CONTEXT_FREERTOS = 3,
+};
+
+typedef struct async_context async_context_t;
+
+/*! \brief A "timeout" instance used by an async_context
+ *  \ingroup pico_async_context
+ *
+ *  A "timeout" represents some future action that must be taken at a specific time.
+ *  It's methods are called from the async_context under lock at the given time
+ *
+ * \see async_context_add_worker_at
+ * \see async_context_add_worker_in_ms
+ */
+typedef struct async_work_on_timeout {
+    /*!
+     * private link list pointer
+     */
+    struct async_work_on_timeout *next;
+    /*!
+     * Method called when the timeout is reached; may not be NULL
+     *
+     * Note, that when this method is called, the timeout has been removed from the async_context, so
+     * if you want the timeout to repeat, you should re-add it during this callback
+     * @param context
+     * @param timeout
+     */
+    void (*do_work)(async_context_t *context, struct async_work_on_timeout *timeout);
+    /*!
+     * The next timeout time; this should only be modified during the above methods
+     * or via async_context methods
+     */
+    absolute_time_t next_time;
+    /*!
+     * User data associated with the timeout instance
+     */
+    void *user_data;
+} async_at_time_worker_t;
+
+/*! \brief A "worker" instance used by an async_context
+ *  \ingroup pico_async_context
+ *
+ *  A "worker" represents some external entity that must do work in response
+ *  to some external stimulus (usually an IRQ).
+ *  It's methods are called from the async_context under lock at the given time
+ *
+ * \see async_context_add_worker_at
+ * \see async_context_add_worker_in_ms
+ */
+typedef struct async_when_pending_worker {
+    /*!
+     * private link list pointer
+     */
+    struct async_when_pending_worker *next;
+    /*!
+     * Called by the async_context when the worker has been marked as having "work pending"
+     *
+     * @param context the async_context
+     * @param worker the function to be called when work is pending
+     */
+    void (*do_work)(async_context_t *context, struct async_when_pending_worker *worker);
+    /**
+     * True if the worker need do_work called
+     */
+    bool work_pending;
+} async_when_pending_worker_t;
+
+#define ASYNC_CONTEXT_FLAG_CALLBACK_FROM_NON_IRQ 0x1
+#define ASYNC_CONTEXT_FLAG_CALLBACK_FROM_IRQ 0x2
+#define ASYNC_CONTEXT_FLAG_POLLED 0x4
+
+/*!
+ * \brief Implementation of an async_context
+ * \ingroup pico_async_context
+ */
+typedef struct async_context_type {
+    uint16_t type;
+    // see wrapper functions for documentation
+    void (*acquire_lock_blocking)(async_context_t *self);
+    void (*release_lock)(async_context_t *self);
+    void (*lock_check)(async_context_t *self);
+    uint32_t (*execute_sync)(async_context_t *context, uint32_t (*func)(void *param), void *param);
+    bool (*add_at_time_worker)(async_context_t *self, async_at_time_worker_t *worker);
+    bool (*remove_at_time_worker)(async_context_t *self, async_at_time_worker_t *worker);
+    bool (*add_when_pending_worker)(async_context_t *self, async_when_pending_worker_t *worker);
+    bool (*remove_when_pending_worker)(async_context_t *self, async_when_pending_worker_t *worker);
+    void (*set_work_pending)(async_context_t *self, async_when_pending_worker_t *worker);
+    void (*poll)(async_context_t *self); // may be NULL
+    void (*wait_until)(async_context_t *self, absolute_time_t until);
+    void (*wait_for_work_until)(async_context_t *self, absolute_time_t until);
+    void (*deinit)(async_context_t *self);
+} async_context_type_t;
+
+struct async_context {
+    const async_context_type_t *type;
+    async_when_pending_worker_t *when_pending_list;
+    async_at_time_worker_t *at_time_list;
+    absolute_time_t next_time;
+    uint16_t flags;
+    uint8_t  core_num;
+};
+
+/*!
+ * \brief Acquire the async_context lock
+ * \ingroup pico_async_context
+ *
+ * The owner of the async_context lock is the logic owner of the async_context
+ * and other work related to this async_context will not happen concurrently.
+ *
+ * This method may be called in a nested fashion by the the lock owner.
+ *
+ * \note the async_context lock is nestable by the same caller, so an internal count is maintained
+ * 
+ * \note for async_contexts that provide locking (not async_context_poll), this method is threadsafe. and may be called from within any 
+ * worker method called by the async_context or from any other non-IRQ context.
+ *
+ * \param context the async_context
+ *
+ * \see async_context_release_lock
+ */
+static inline void async_context_acquire_lock_blocking(async_context_t *context) {
+    context->type->acquire_lock_blocking(context);
+}
+
+/*!
+ * \brief Release the async_context lock
+ * \ingroup pico_async_context
+ *
+ * \note the async_context lock may be called in a nested fashion, so an internal count is maintained. On the outermost
+ * release, When the outermost lock is released, a check is made for work which might have been skipped while the lock was held,
+ * and any such work may be performed during this call IF the call is made from the same core that the async_context belongs to.
+ *
+ * \note for async_contexts that provide locking (not async_context_poll), this method is threadsafe. and may be called from within any 
+ * worker method called by the async_context or from any other non-IRQ context.
+ *
+ * \param context the async_context
+ *
+ * \see async_context_acquire_lock_blocking
+ */
+static inline void async_context_release_lock(async_context_t *context) {
+    context->type->release_lock(context);
+}
+
+/*!
+ * \brief Assert if the caller does not own the lock for the async_context
+ * \ingroup pico_async_context
+ * \note this method is thread-safe
+ *
+ * \param context the async_context
+ */
+static inline void async_context_lock_check(async_context_t *context) {
+    context->type->lock_check(context);
+}
+
+/*!
+ * \brief Execute work synchronously on the core the async_context belongs to.
+ * \ingroup pico_async_context
+ *
+ * This method is intended for code external to the async_context (e.g. another thread/task) to
+ * execute a function with the same guarantees (single core, logical thread of execution) that
+ * async_context workers are called with.
+ *
+ * \note you should NOT call this method while holding the async_context's lock
+ *
+ * \param context the async_context
+ * \param func the function to call
+ * \param parm the paramter to pass to the function
+ * \return the return value from func
+ */
+static inline uint32_t async_context_execute_sync(async_context_t *context, uint32_t (*func)(void *param), void *param) {
+    return context->type->execute_sync(context, func, param);
+}
+
+/*!
+ * \brief Add an "at time" worker to a context
+ * \ingroup pico_async_context
+ *
+ * An "at time" worker will run at or after a specific point in time, and is automatically when (just before) it runs.
+ *
+ * The time to fire is specified in the next_time field of the worker.
+ *
+ * \note for async_contexts that provide locking (not async_context_poll), this method is threadsafe. and may be called from within any 
+ * worker method called by the async_context or from any other non-IRQ context.
+ *
+ * \param context the async_context
+ * \param worker the "at time" worker to add
+ * \return true if the worker was added, false if the worker was already present.
+ */
+static inline bool async_context_add_at_time_worker(async_context_t *context, async_at_time_worker_t *worker) {
+    return context->type->add_at_time_worker(context, worker);
+}
+
+/*!
+ * \brief Add an "at time" worker to a context
+ * \ingroup pico_async_context
+ *
+ * An "at time" worker will run at or after a specific point in time, and is automatically when (just before) it runs.
+ *
+ * The time to fire is specified by the at parameter.
+ *
+ * \note for async_contexts that provide locking (not async_context_poll), this method is threadsafe. and may be called from within any 
+ * worker method called by the async_context or from any other non-IRQ context.
+ *
+ * \param context the async_context
+ * \param worker the "at time" worker to add
+ * \param at the time to fire at
+ * \return true if the worker was added, false if the worker was already present.
+ */
+static inline bool async_context_add_at_time_worker_at(async_context_t *context, async_at_time_worker_t *worker, absolute_time_t at) {
+    worker->next_time = at;
+    return context->type->add_at_time_worker(context, worker);
+}
+
+/*!
+ * \brief Add an "at time" worker to a context
+ * \ingroup pico_async_context
+ *
+ * An "at time" worker will run at or after a specific point in time, and is automatically when (just before) it runs.
+ *
+ * The time to fire is specified by a delay via the ms parameter 
+ *
+ * \note for async_contexts that provide locking (not async_context_poll), this method is threadsafe. and may be called from within any 
+ * worker method called by the async_context or from any other non-IRQ context.
+ *
+ * \param context the async_context
+ * \param worker the "at time" worker to add
+ * \param ms the number of milliseconds from now to fire after
+ * \return true if the worker was added, false if the worker was already present.
+ */
+static inline bool async_context_add_at_time_worker_in_ms(async_context_t *context, async_at_time_worker_t *worker, uint32_t ms) {
+    worker->next_time = make_timeout_time_ms(ms);
+    return context->type->add_at_time_worker(context, worker);
+}
+
+/*!
+ * \brief Remove an "at time" worker from a context
+ * \ingroup pico_async_context
+ *
+ * \note for async_contexts that provide locking (not async_context_poll), this method is threadsafe. and may be called from within any 
+ * worker method called by the async_context or from any other non-IRQ context.
+ *
+ * \param context the async_context
+ * \param worker the "at time" worker to remove
+ * \return true if the worker was removed, false if the instance not present.
+ */
+static inline bool async_context_remove_at_time_worker(async_context_t *context, async_at_time_worker_t *worker) {
+    return context->type->remove_at_time_worker(context, worker);
+}
+
+/*!
+ * \brief Add a "when pending" worker to a context
+ * \ingroup pico_async_context
+ *
+ * An "when pending" worker will run when it is pending (can be set via \ref async_context_set_work_pending), and
+ * is NOT automatically removed when it runs.
+ *
+ * The time to fire is specified by a delay via the ms parameter
+ *
+ * \note for async_contexts that provide locking (not async_context_poll), this method is threadsafe. and may be called from within any 
+ * worker method called by the async_context or from any other non-IRQ context.
+ *
+ * \param context the async_context
+ * \param worker the "when pending" worker to add
+ * \return true if the worker was added, false if the worker was already present.
+ */
+static inline bool async_context_add_when_pending_worker(async_context_t *context, async_when_pending_worker_t *worker) {
+    return context->type->add_when_pending_worker(context, worker);
+}
+
+/*!
+ * \brief Remove a "when pending" worker from a context
+ * \ingroup pico_async_context
+ *
+ * \note for async_contexts that provide locking (not async_context_poll), this method is threadsafe. and may be called from within any 
+ * worker method called by the async_context or from any other non-IRQ context.
+ *
+ * \param context the async_context
+ * \param worker the "when pending" worker to remove
+ * \return true if the worker was removed, false if the instance not present.
+ */
+static inline bool async_context_remove_when_pending_worker(async_context_t *context, async_when_pending_worker_t *worker) {
+    return context->type->remove_when_pending_worker(context, worker);
+}
+
+/*!
+ * \brief Mark a "when pending" worker as having work pending
+ * \ingroup pico_async_context
+ *
+ * The worker will be run from the async_context at a later time.
+ *
+ * \note this method may be called from any context including IRQs
+ *
+ * \param context the async_context
+ * \param worker the "when pending" worker to mark as pending.
+ */
+static inline void async_context_set_work_pending(async_context_t *context, async_when_pending_worker_t *worker) {
+    context->type->set_work_pending(context, worker);
+}
+
+/*!
+ * \brief Perform any pending work for polling style async_context
+ * \ingroup pico_async_context
+ * 
+ * For a polled async_context (e.g. \ref async_context_poll) the user is responsible for calling this method
+ * periodically to perform any required work.
+ * 
+ * This method may immediately perform outstanding work on other context types, but is not required to.
+ *
+ * \param context the async_context
+ */
+static inline void async_context_poll(async_context_t *context) {
+    if (context->type->poll) context->type->poll(context);
+}
+
+/*!
+ * \brief sleep until the specified time in an async_context callback safe way
+ * \ingroup pico_async_context
+ *
+ * \note for async_contexts that provide locking (not async_context_poll), this method is threadsafe. and may be called from within any
+ * worker method called by the async_context or from any other non-IRQ context.
+ *
+ * \param context the async_context
+ * \param until the time to sleep until
+ */
+static inline void async_context_wait_until(async_context_t *context, absolute_time_t until) {
+    context->type->wait_until(context, until);
+}
+
+/*!
+ * \brief Block until work needs to be done or the specified time has been reached
+ * \ingroup pico_async_context
+ *
+ * \note this method should not be called from a worker callback
+ *
+ * \param context the async_context
+ * \param until the time to return at if no work is required
+ */
+static inline void async_context_wait_for_work_until(async_context_t *context, absolute_time_t until) {
+    context->type->wait_for_work_until(context, until);
+}
+
+/*!
+ * \brief Block until work needs to be done or the specified number of milliseconds have passed
+ * \ingroup pico_async_context
+ *
+ * \note this method should not be called from a worker callback
+ *
+ * \param context the async_context
+ * \param ms the number of milliseconds to return after if no work is required
+ */
+static inline void async_context_wait_for_work_ms(async_context_t *context, uint32_t ms) {
+    async_context_wait_for_work_until(context, make_timeout_time_ms(ms));
+}
+
+/*!
+ * \brief Return the processor core this async_context belongs to
+ * \ingroup pico_async_context
+ *
+ * \param context the async_context
+ * \return the physical core number
+ */
+static inline uint async_context_core_num(const async_context_t *context) {
+    return context->core_num;
+}
+
+/*!
+ * \brief End async_context processing, and free any resources
+ * \ingroup pico_async_context
+ *
+ * Note the user should clean up any resources associated with workers
+ * in the async_context themselves.
+ *
+ * Asynchronous (non-polled) async_contexts guarantee that no
+ * callback is being called once this method returns.
+ *
+ * \param context the async_context
+ * \return the physical core number
+ */
+static inline void async_context_deinit(async_context_t *context) {
+    context->type->deinit(context);
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

src/rp2_common/pico_async_context/include/pico/async_context_base.h

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2022 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef _PICO_ASYNC_CONTEXT_BASE_H
+#define _PICO_ASYNC_CONTEXT_BASE_H
+
+#include "pico/async_context.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// common functions for async_context implementations to use
+bool async_context_base_add_at_time_worker(async_context_t *self, async_at_time_worker_t *worker);
+bool async_context_base_remove_at_time_worker(async_context_t *self, async_at_time_worker_t *worker);
+
+bool async_context_base_add_when_pending_worker(async_context_t *self, async_when_pending_worker_t *worker);
+bool async_context_base_remove_when_pending_worker(async_context_t *self, async_when_pending_worker_t *worker);
+
+async_at_time_worker_t *async_context_base_remove_ready_at_time_worker(async_context_t *self);
+void async_context_base_refresh_next_timeout(async_context_t *self);
+
+absolute_time_t async_context_base_execute_once(async_context_t *self);
+bool async_context_base_needs_servicing(async_context_t *self);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

src/rp2_common/pico_async_context/include/pico/async_context_freertos.h

@@ -0,0 +1,120 @@
+/*
+ * Copyright (c) 2022 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef _PICO_ASYNC_CONTEXT_FREERTOS_H
+#define _PICO_ASYNC_CONTEXT_FREERTOS_H
+
+/** \file pico/async_context.h
+ *  \defgroup async_context_freertos async_context_freertos
+ *  \ingroup pico_async_context
+ *  
+ * async_context_freertos provides an implementation of \ref async_context that handles asynchronous
+ * work in a separate FreeRTOS task.
+ */
+#include "pico/async_context.h"
+
+// FreeRTOS includes
+#include "FreeRTOS.h"
+#include "semphr.h"
+#include "timers.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef ASYNC_CONTEXT_DEFAULT_FREERTOS_TASK_PRIORITY
+#define ASYNC_CONTEXT_DEFAULT_FREERTOS_TASK_PRIORITY ( tskIDLE_PRIORITY + 4)
+#endif
+
+#ifndef ASYNC_CONTEXT_DEFAULT_FREERTOS_TASK_STACK_SIZE
+#define ASYNC_CONTEXT_DEFAULT_FREERTOS_TASK_STACK_SIZE configMINIMAL_STACK_SIZE
+#endif
+
+typedef struct async_context_freertos async_context_freertos_t;
+
+/** 
+ * \brief Configuration object for async_context_freertos instances.
+ */
+typedef struct async_context_freertos_config {
+    /**
+     * Task priority for the async_context task
+     */
+    UBaseType_t task_priority;
+    /**
+     * Stack size for the async_context task
+     */
+    configSTACK_DEPTH_TYPE task_stack_size;
+    /**
+     * the core ID (see \ref portGET_CORE_ID()) to pin the task to.
+     * This is only relevant in SMP mode.
+     */
+#if configUSE_CORE_AFFINITY && configNUM_CORES > 1
+    UBaseType_t task_core_id;
+#endif
+} async_context_freertos_config_t;
+
+struct async_context_freertos {
+    async_context_t core;
+    SemaphoreHandle_t lock_mutex;
+    SemaphoreHandle_t work_needed_sem;
+    TimerHandle_t timer_handle;
+    TaskHandle_t task_handle;
+    uint8_t nesting;
+    volatile bool task_should_exit;
+};
+
+/*!
+ * \brief Initialize an async_context_freertos instance using the specified configuration
+ * \ingroup async_context_freertos
+ *
+ * If this method succeeds (returns true), then the async_context is available for use
+ * and can be de-initialized by calling async_context_deinit().
+ * 
+ * \param self a pointer to async_context_freertos structure to initialize
+ * \param config the configuration object specifying characteristics for the async_context
+ * \return true if initialization is successful, false otherwise
+ */
+bool async_context_freertos_init(async_context_freertos_t *self, async_context_freertos_config_t *config);
+
+/*!
+ * \brief Return a copy of the default configuration object used by \ref async_context_freertos_init_with_defaults() 
+ * \ingroup async_context_freertos
+ *
+ * The caller can then modify just the settings it cares about, and call \ref async_context_threasafe_background_init()
+ * \return the default configuration object
+ */
+ static inline async_context_freertos_config_t async_context_freertos_default_config(void) {
+    async_context_freertos_config_t config = {
+            .task_priority = ASYNC_CONTEXT_DEFAULT_FREERTOS_TASK_PRIORITY,
+            .task_stack_size = ASYNC_CONTEXT_DEFAULT_FREERTOS_TASK_STACK_SIZE,
+#if configUSE_CORE_AFFINITY
+            .task_core_id = (UBaseType_t)-1, // none
+#endif
+    };
+    return config;
+
+}
+
+/*!
+ * \brief Initialize an async_context_freertos instance with default values
+ * \ingroup async_context_freertos
+ *
+ * If this method succeeds (returns true), then the async_context is available for use
+ * and can be de-initialized by calling async_context_deinit().
+ * 
+ * \param self a pointer to async_context_freertos structure to initialize
+ * \return true if initialization is successful, false otherwise
+ */
+ static inline bool async_context_freertos_init_with_defaults(async_context_freertos_t *self) {
+    async_context_freertos_config_t config = async_context_freertos_default_config();
+    return async_context_freertos_init(self, &config);
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

src/rp2_common/pico_async_context/include/pico/async_context_poll.h

@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2022 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef _PICO_ASYNC_CONTEXT_POLL_H
+#define _PICO_ASYNC_CONTEXT_POLL_H
+
+/** \file pico/async_context.h
+ *  \defgroup async_context_poll async_context_poll
+ *  \ingroup pico_async_context
+ *
+ * async_context_poll provides an implementation of \ref async_context that is intended for use with a simple
+ * polling loop on one core. It is not thread safe.
+ *
+ * The \ref async_context_poll() method must be called periodically to handle asynchronous work that may now be
+ * pending. \ref async_context_wait_for_work_until() may be used to block a polling loop until there is work to do,
+ * and prevent tight spinning.
+ */
+#include "pico/async_context.h"
+#include "pico/sem.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct async_context_poll {
+    async_context_t core;
+    semaphore_t sem;
+} async_context_poll_t;
+
+/*!
+ * \brief Initialize an async_context_poll instance with default values
+ * \ingroup async_context_poll
+ *
+ * If this method succeeds (returns true), then the async_context is available for use
+ * and can be de-initialized by calling async_context_deinit().
+ *
+ * \param self a pointer to async_context_poll structure to initialize
+ * \return true if initialization is successful, false otherwise
+ */
+bool async_context_poll_init_with_defaults(async_context_poll_t *self);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

src/rp2_common/pico_async_context/include/pico/async_context_threadsafe_background.h

@@ -0,0 +1,112 @@
+/*
+ * Copyright (c) 2022 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef _PICO_ASYNC_CONTEXT_THREADSAFE_BACKGROUND_H
+#define _PICO_ASYNC_CONTEXT_THREADSAFE_BACKGROUND_H
+
+/** \file pico/async_context.h
+ *  \defgroup async_context_threadsafe_background async_context_threadsafe_background
+ *  \ingroup pico_async_context
+ *  
+ * async_context_threadsafe_background provides an implementation of \ref async_context that handles asynchronous
+ * work in a low priority IRQ, and there is no need for the user to poll for work.
+ *
+ * \note The workers used with this async_context MUST be safe to call from an IRQ.
+ */
+
+#include "pico/async_context.h"
+#include "pico/sem.h"
+#include "pico/mutex.h"
+#include "hardware/irq.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef ASYNC_CONTEXT_THREADSAFE_BACKGROUND_MULTI_CORE
+#define ASYNC_CONTEXT_THREADSAFE_BACKGROUND_MULTI_CORE LIB_PICO_MULTICORE
+#endif
+
+typedef struct async_context_threadsafe_background async_context_threadsafe_background_t;
+
+/**
+ * \brief Configuration object for async_context_threadsafe_background instances.
+ */
+typedef struct async_context_threadsafe_background_config {
+/**
+ * the priority of the low priority IRQ
+ */
+    uint8_t low_priority_irq_handler_priority;
+    /**
+     * a specific alarm pool to use (or NULL to use ta default)
+     *
+     * \note this alarm pool MUST be on the same core as the async_context
+     *
+     * The default alarm pool used is the "default alarm pool" (see
+     * \ref alarm_pool_get_default()) if available, and if that is on the same
+     * core, otherwise a private alarm_pool instance created during
+     * initialization.
+     */
+    alarm_pool_t *custom_alarm_pool;
+} async_context_threadsafe_background_config_t;
+
+struct async_context_threadsafe_background {
+    async_context_t core;
+    alarm_pool_t *alarm_pool; // this must be on the same core as core_num
+    absolute_time_t last_set_alarm_time;
+    recursive_mutex_t lock_mutex;
+    semaphore_t work_needed_sem;
+    volatile alarm_id_t alarm_id;
+#if ASYNC_CONTEXT_THREADSAFE_BACKGROUND_MULTI_CORE
+    volatile alarm_id_t force_alarm_id;
+    bool alarm_pool_owned;
+#endif
+    uint8_t low_priority_irq_num;
+    volatile bool alarm_pending;
+};
+
+/*!
+ * \brief Initialize an async_context_threadsafe_background instance using the specified configuration
+ * \ingroup async_context_threadsafe_background
+ *
+ * If this method succeeds (returns true), then the async_context is available for use
+ * and can be de-initialized by calling async_context_deinit().
+ * 
+ * \param self a pointer to async_context_threadsafe_background structure to initialize
+ * \param config the configuration object specifying characteristics for the async_context
+ * \return true if initialization is successful, false otherwise
+ */
+bool async_context_threadsafe_background_init(async_context_threadsafe_background_t *self, async_context_threadsafe_background_config_t *config);
+
+/*!
+ * \brief Return a copy of the default configuration object used by \ref async_context_threadsafe_background_init_with_defaults() 
+ * \ingroup async_context_threadsafe_background
+ *
+ * The caller can then modify just the settings it cares about, and call \ref async_context_threasafe_background_init()
+ * \return the default configuration object
+ */
+async_context_threadsafe_background_config_t async_context_threadsafe_background_default_config(void);
+
+/*!
+ * \brief Initialize an async_context_threadsafe_background instance with default values
+ * \ingroup async_context_threadsafe_background
+ *
+ * If this method succeeds (returns true), then the async_context is available for use
+ * and can be de-initialized by calling async_context_deinit().
+ * 
+ * \param self a pointer to async_context_threadsafe_background structure to initialize
+ * \return true if initialization is successful, false otherwise
+ */
+static inline bool async_context_threadsafe_background_init_with_defaults(async_context_threadsafe_background_t *self) {
+    async_context_threadsafe_background_config_t config = async_context_threadsafe_background_default_config();
+    return async_context_threadsafe_background_init(self, &config);
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

src/rp2_common/pico_bootrom/include/pico/bootrom.h

@@ -130,7 +130,7 @@ static inline void *rom_hword_as_ptr(uint16_t rom_address) {
 #endif
 
 /*!
- * \brief Lookup a bootrom function by code. This method is forceably inlined into the caller for FLASH/RAM sensitive code usage
+ * \brief Lookup a bootrom function by code. This method is forcibly inlined into the caller for FLASH/RAM sensitive code usage
  * \ingroup pico_bootrom
  * \param code the code
  * \return a pointer to the function, or NULL if the code does not match any bootrom function

src/rp2_common/pico_cyw43_arch/CMakeLists.txt

@@ -1,7 +1,5 @@
 if (PICO_CYW43_SUPPORTED) # set by BOARD=pico-w
     if (TARGET cyw43_driver_picow)
-        message("Enabling build support for Pico W wireless.")
-
         pico_add_impl_library(pico_cyw43_arch)
         target_sources(pico_cyw43_arch INTERFACE
                 ${CMAKE_CURRENT_LIST_DIR}/cyw43_arch.c
@@ -15,45 +13,70 @@ if (PICO_CYW43_SUPPORTED) # set by BOARD=pico-w
 
         target_link_libraries(pico_cyw43_arch INTERFACE
                 pico_unique_id
-                cyw43_driver_picow)
+                cyw43_driver_picow # driver for pico w
+                pico_cyw43_driver # integration with async_context
+                )
 
         if (NOT TARGET pico_lwip)
-            message(WARNING "lwIP is not available; Full Pico W wireless support will be unavailable too")
+            message(WARNING "lwIP is not available; Full Pico W wireless support will be unavailable")
         else()
-            add_library(pico_cyw43_arch_lwip_poll INTERFACE)
+            message("Pico W wireless build support available.")
-            target_link_libraries(pico_cyw43_arch_lwip_poll INTERFACE
+            add_library(pico_cyw43_arch_poll INTERFACE)
+            target_link_libraries(pico_cyw43_arch_poll INTERFACE
                     pico_cyw43_arch
-                    pico_lwip
+                    pico_async_context_poll)
-                    pico_lwip_nosys)
+            target_compile_definitions(pico_cyw43_arch_poll INTERFACE
-            target_compile_definitions(pico_cyw43_arch_lwip_poll INTERFACE
-                    CYW43_LWIP=1
                     PICO_CYW43_ARCH_POLL=1
                     )
 
-            add_library(pico_cyw43_arch_lwip_threadsafe_background INTERFACE)
+            add_library(pico_cyw43_arch_lwip_poll INTERFACE)
-            target_link_libraries(pico_cyw43_arch_lwip_threadsafe_background INTERFACE
+            target_link_libraries(pico_cyw43_arch_lwip_poll INTERFACE
+                    pico_lwip_nosys
+                    pico_cyw43_arch_poll)
+            target_compile_definitions(pico_cyw43_arch_lwip_poll INTERFACE
+                    CYW43_LWIP=1
+                    )
+
+            add_library(pico_cyw43_arch_threadsafe_background INTERFACE)
+            target_link_libraries(pico_cyw43_arch_threadsafe_background INTERFACE
                     pico_cyw43_arch
-                    pico_lwip
+                    pico_async_context_threadsafe_background)
-                    pico_lwip_nosys)
+            target_compile_definitions(pico_cyw43_arch_threadsafe_background INTERFACE
+                    PICO_CYW43_ARCH_THREADSAFE_BACKGROUND=1
+                    )
+            add_library(pico_cyw43_arch_lwip_threadsafe_background INTERFACE)
+
+            target_link_libraries(pico_cyw43_arch_lwip_threadsafe_background INTERFACE
+                    pico_lwip_nosys
+                    pico_cyw43_arch_threadsafe_background)
             target_compile_definitions(pico_cyw43_arch_lwip_threadsafe_background INTERFACE
                     CYW43_LWIP=1
-                    PICO_CYW43_ARCH_THREADSAFE_BACKGROUND=1
+                    )
+
+            add_library(pico_cyw43_arch_sys_freertos INTERFACE)
+            target_link_libraries(pico_cyw43_arch_sys_freertos INTERFACE
+                    pico_cyw43_arch
+                    pico_async_context_freertos)
+            target_compile_definitions(pico_cyw43_arch_sys_freertos INTERFACE
+                    PICO_CYW43_ARCH_FREERTOS=1
                     )
 
             add_library(pico_cyw43_arch_lwip_sys_freertos INTERFACE)
             target_link_libraries(pico_cyw43_arch_lwip_sys_freertos INTERFACE
-                    pico_cyw43_arch
+                    pico_lwip_freertos
-                    pico_lwip
+                    pico_cyw43_arch_sys_freertos)
-                    pico_lwip_contrib_freertos)
             target_compile_definitions(pico_cyw43_arch_lwip_sys_freertos INTERFACE
                     CYW43_LWIP=1
                     LWIP_PROVIDE_ERRNO=1
-                    PICO_CYW43_ARCH_FREERTOS=1
+                    # now the default
+                    #PICO_LWIP_CUSTOM_LOCK_TCPIP_CORE=1 # we want to override the lwip locking mechanism to use our mutex
                     )
         endif()
 
         add_library(pico_cyw43_arch_none INTERFACE)
-        target_link_libraries(pico_cyw43_arch_none INTERFACE pico_cyw43_arch)
+        target_link_libraries(pico_cyw43_arch_none INTERFACE
+                pico_cyw43_arch
+                pico_async_context_threadsafe_background)
         target_compile_definitions(pico_cyw43_arch_none INTERFACE
                 CYW43_LWIP=0
                 PICO_CYW43_ARCH_THREADSAFE_BACKGROUND=1 # none still uses threadsafe_background to make gpio use easy

src/rp2_common/pico_cyw43_arch/cyw43_arch.c

@@ -14,7 +14,7 @@
 #include "cyw43_ll.h"
 #include "cyw43_stats.h"
 
-#if CYW43_ARCH_DEBUG_ENABLED
+#if PICO_CYW43_ARCH_DEBUG_ENABLED
 #define CYW43_ARCH_DEBUG(...) printf(__VA_ARGS__)
 #else
 #define CYW43_ARCH_DEBUG(...) ((void)0)
@@ -22,6 +22,12 @@
 
 static uint32_t country_code = PICO_CYW43_ARCH_DEFAULT_COUNTRY_CODE;
 
+static async_context_t *async_context;
+
+void cyw43_arch_set_async_context(async_context_t *context) {
+    async_context = context;
+}
+
 void cyw43_arch_enable_sta_mode() {
     assert(cyw43_is_initialized(&cyw43_state));
     cyw43_wifi_set_up(&cyw43_state, CYW43_ITF_STA, true, cyw43_arch_get_country_code());
@@ -39,9 +45,9 @@ void cyw43_arch_enable_ap_mode(const char *ssid, const char *password, uint32_t
     cyw43_wifi_set_up(&cyw43_state, CYW43_ITF_AP, true, cyw43_arch_get_country_code());
 }
 
-#if CYW43_ARCH_DEBUG_ENABLED
+#if PICO_CYW43_ARCH_DEBUG_ENABLED
 // Return a string for the wireless state
-static const char* status_name(int status)
+const char* cyw43_tcpip_link_status_name(int status)
 {
     switch (status) {
     case CYW43_LINK_DOWN:
@@ -79,14 +85,14 @@ int cyw43_arch_wifi_connect_until(const char *ssid, const char *pw, uint32_t aut
         int new_status = cyw43_tcpip_link_status(&cyw43_state, CYW43_ITF_STA);
         if (new_status != status) {
             status = new_status;
-            CYW43_ARCH_DEBUG("connect status: %s\n", status_name(status));
+            CYW43_ARCH_DEBUG("connect status: %s\n", cyw43_tcpip_link_status_name(status));
         }
-        // in case polling is required
-        cyw43_arch_poll();
-        best_effort_wfe_or_timeout(until);
         if (time_reached(until)) {
             return PICO_ERROR_TIMEOUT;
         }
+        // Do polling
+        cyw43_arch_poll();
+        cyw43_arch_wait_for_work_until(until);
     }
     return status == CYW43_LINK_UP ? 0 : status;
 }
@@ -143,3 +149,64 @@ bool cyw43_arch_gpio_get(uint wl_gpio) {
     cyw43_gpio_get(&cyw43_state, (int)wl_gpio, &value);
     return value;
 }
+
+async_context_t *cyw43_arch_async_context(void) {
+    return async_context;
+}
+
+void cyw43_arch_poll(void)
+{
+    async_context_poll(async_context);
+}
+
+void cyw43_arch_wait_for_work_until(absolute_time_t until) {
+    async_context_wait_for_work_until(async_context, until);
+}
+
+// Prevent background processing in pensv and access by the other core
+// These methods are called in pensv context and on either core
+// They can be called recursively
+void cyw43_thread_enter(void) {
+    async_context_acquire_lock_blocking(async_context);
+}
+
+void cyw43_thread_exit(void) {
+    async_context_release_lock(async_context);
+}
+
+#ifndef NDEBUG
+void cyw43_thread_lock_check(void) {
+    async_context_lock_check(async_context);
+}
+#endif
+
+void cyw43_await_background_or_timeout_us(uint32_t timeout_us) {
+    async_context_wait_for_work_until(async_context, make_timeout_time_us(timeout_us));
+}
+
+void cyw43_delay_ms(uint32_t ms) {
+    async_context_wait_until(async_context, make_timeout_time_ms(ms));
+}
+
+void cyw43_delay_us(uint32_t us) {
+    async_context_wait_until(async_context, make_timeout_time_us(us));
+}
+
+#if !CYW43_LWIP
+static void no_lwip_fail() {
+    panic("cyw43 has no ethernet interface");
+}
+void __attribute__((weak)) cyw43_cb_tcpip_init(cyw43_t *self, int itf) {
+}
+void __attribute__((weak)) cyw43_cb_tcpip_deinit(cyw43_t *self, int itf) {
+}
+void __attribute__((weak)) cyw43_cb_tcpip_set_link_up(cyw43_t *self, int itf) {
+    no_lwip_fail();
+}
+void __attribute__((weak)) cyw43_cb_tcpip_set_link_down(cyw43_t *self, int itf) {
+    no_lwip_fail();
+}
+void __attribute__((weak)) cyw43_cb_process_ethernet(void *cb_data, int itf, size_t len, const uint8_t *buf) {
+    no_lwip_fail();
+}
+#endif

src/rp2_common/pico_cyw43_arch/cyw43_arch_freertos.c

@@ -4,250 +4,71 @@
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
-#include <stdio.h>
+#if PICO_CYW43_ARCH_FREERTOS
 
 #include "pico/cyw43_arch.h"
-
+#include "pico/cyw43_driver.h"
-#include "hardware/gpio.h"
+#include "pico/async_context_freertos.h"
-#include "hardware/irq.h"
-#include "hardware/sync.h"
-
-#include "cyw43_stats.h"
 
 #if CYW43_LWIP
+#include "pico/lwip_freertos.h"
 #include <lwip/tcpip.h>
 #endif
 
-#if PICO_CYW43_ARCH_FREERTOS
-
-// FreeRTOS includes
-#include "FreeRTOS.h"
-#include "timers.h"
-#include "semphr.h"
-
 #if NO_SYS
-#error example_cyw43_arch_frertos_sys requires NO_SYS=0
+#error example_cyw43_arch_freetos_sys requires NO_SYS=0
 #endif
 
-#ifndef CYW43_TASK_PRIORITY
+static async_context_freertos_t cyw43_async_context_freertos;
-#define CYW43_TASK_PRIORITY ( tskIDLE_PRIORITY + 4)
+
+async_context_t *cyw43_arch_init_default_async_context(void) {
+    async_context_freertos_config_t config = async_context_freertos_default_config();
+#ifdef CYW43_TASK_PRIORITY
+    config.task_priority = CYW43_TASK_PRIORITY;
 #endif
-
+#ifdef CYW43_TASK_STACK_SIZE
-#ifndef CYW43_SLEEP_CHECK_MS
+    config.task_stack_size = CYW43_TASK_STACK_SIZE;
-#define CYW43_SLEEP_CHECK_MS 50 // How often to run lwip callback
 #endif
-
+    if (async_context_freertos_init(&cyw43_async_context_freertos, &config))
-#define CYW43_GPIO_IRQ_HANDLER_PRIORITY 0x40
+        return &cyw43_async_context_freertos.core;
-
+    return NULL;
-static void signal_cyw43_task(void);
-
-#if !LWIP_TCPIP_CORE_LOCKING_INPUT
-static SemaphoreHandle_t cyw43_mutex;
-#endif
-static TimerHandle_t timer_handle;
-static TaskHandle_t cyw43_task_handle;
-static volatile bool cyw43_task_should_exit;
-static SemaphoreHandle_t cyw43_worker_ran_sem;
-static uint8_t cyw43_core_num;
-
-// Called in low priority pendsv interrupt only to do lwip processing and check cyw43 sleep
-static void periodic_worker(__unused TimerHandle_t handle)
-{
-#if CYW43_USE_STATS
-    static uint32_t counter;
-    if (counter++ % (30000 / LWIP_SYS_CHECK_MS) == 0) {
-        cyw43_dump_stats();
-    }
-#endif
-
-    CYW43_STAT_INC(LWIP_RUN_COUNT);
-    if (cyw43_poll) {
-        if (cyw43_sleep > 0) {
-            if (--cyw43_sleep == 0) {
-                signal_cyw43_task();
-            }
-        }
-    }
-}
-
-void cyw43_await_background_or_timeout_us(uint32_t timeout_us) {
-    // if we are called from within an IRQ, then don't wait (we are only ever called in a polling loop)
-    assert(!portCHECK_IF_IN_ISR());
-    xSemaphoreTake(cyw43_worker_ran_sem, pdMS_TO_TICKS(timeout_us / 1000));
-}
-
-// GPIO interrupt handler to tell us there's cyw43 has work to do
-static void gpio_irq_handler(void)
-{
-    uint32_t events = gpio_get_irq_event_mask(CYW43_PIN_WL_HOST_WAKE);
-    if (events & GPIO_IRQ_LEVEL_HIGH) {
-        // As we use a high level interrupt, it will go off forever until it's serviced
-        // So disable the interrupt until this is done. It's re-enabled again by CYW43_POST_POLL_HOOK
-        // which is called at the end of cyw43_poll_func
-        gpio_set_irq_enabled(CYW43_PIN_WL_HOST_WAKE, GPIO_IRQ_LEVEL_HIGH, false);
-        signal_cyw43_task();
-        CYW43_STAT_INC(IRQ_COUNT);
-    }
-}
-
-// Low priority interrupt handler to perform background processing
-static void cyw43_task(__unused void *param) {
-    do {
-        ulTaskNotifyTake(pdFALSE, portMAX_DELAY);
-        if (cyw43_task_should_exit) break;
-        cyw43_thread_enter();
-        if (cyw43_poll) cyw43_poll();
-        cyw43_thread_exit();
-        xSemaphoreGive(cyw43_worker_ran_sem);
-        __sev(); // it is possible regular code is waiting on a WFE on the other core
-    } while (true);
-    vTaskDelete(NULL);
-}
-
-static void tcpip_init_done(void *param) {
-    xSemaphoreGive((SemaphoreHandle_t)param);
 }
 
 int cyw43_arch_init(void) {
-    cyw43_core_num = get_core_num();
+    async_context_t *context = cyw43_arch_async_context();
-#if configUSE_CORE_AFFINITY && configNUM_CORES > 1
+    if (!context) {
-    TaskHandle_t task_handle = xTaskGetCurrentTaskHandle();
+        context = cyw43_arch_init_default_async_context();
-    UBaseType_t affinity = vTaskCoreAffinityGet(task_handle);
+        if (!context) return PICO_ERROR_GENERIC;
-    // we must bind the main task to one core during init
+        cyw43_arch_set_async_context(context);
-    vTaskCoreAffinitySet(task_handle, 1 << portGET_CORE_ID());
-#endif
-#if !LWIP_TCPIP_CORE_LOCKING_INPUT
-    cyw43_mutex = xSemaphoreCreateRecursiveMutex();
-#endif
-    cyw43_init(&cyw43_state);
-    cyw43_worker_ran_sem = xSemaphoreCreateBinary();
-
-#if CYW43_LWIP
-    SemaphoreHandle_t init_sem = xSemaphoreCreateBinary();
-    tcpip_init(tcpip_init_done, init_sem);
-    xSemaphoreTake(init_sem, portMAX_DELAY);
-#endif
-
-    timer_handle = xTimerCreate(    "cyw43_sleep_timer",       // Just a text name, not used by the kernel.
-                                    pdMS_TO_TICKS(CYW43_SLEEP_CHECK_MS),
-                                    pdTRUE,        // The timers will auto-reload themselves when they expire.
-                                    NULL,
-                                    periodic_worker);
-
-    if (!timer_handle) {
-        return PICO_ERROR_GENERIC;
     }
-
+    bool ok = cyw43_driver_init(context);
-    gpio_add_raw_irq_handler_with_order_priority(CYW43_PIN_WL_HOST_WAKE, gpio_irq_handler, CYW43_GPIO_IRQ_HANDLER_PRIORITY);
+#if CYW43_LWIP
-    gpio_set_irq_enabled(CYW43_PIN_WL_HOST_WAKE, GPIO_IRQ_LEVEL_HIGH, true);
+    ok &= lwip_freertos_init(context);
-    irq_set_enabled(IO_IRQ_BANK0, true);
-
-    cyw43_task_should_exit = false;
-    xTaskCreate(cyw43_task, "CYW43 Worker", configMINIMAL_STACK_SIZE, NULL, CYW43_TASK_PRIORITY, &cyw43_task_handle);
-#if configUSE_CORE_AFFINITY && configNUM_CORES > 1
-    // the cyw43 task mus tbe on the same core so it can restore IRQs
-    vTaskCoreAffinitySet(cyw43_task_handle, 1 << portGET_CORE_ID());
 #endif
-
+    if (!ok) {
-#if configUSE_CORE_AFFINITY && configNUM_CORES > 1
+        cyw43_arch_deinit();
-    vTaskCoreAffinitySet(task_handle, affinity);
+        return PICO_ERROR_GENERIC;
-#endif
+    } else {
-
+        return 0;
-    return PICO_OK;
+    }
 }
 
 void cyw43_arch_deinit(void) {
-    assert(cyw43_core_num == get_core_num());
+    async_context_t *context = cyw43_arch_async_context();
-    if (timer_handle) {
+    // there is a bit of a circular dependency here between lwIP and cyw43_driver. We
-        xTimerDelete(timer_handle, 0);
+    // shut down cyw43_driver first as it has IRQs calling back into lwIP. Also lwIP itself
-        timer_handle = 0;
+    // does not actually get shut down.
-    }
+    // todo add a "pause" method to async_context if we need to provide some atomicity (we
-    if (cyw43_task_handle) {
+    //      don't want to take the lock as these methods may invoke execute_sync()
-        cyw43_task_should_exit = true;
+    cyw43_driver_deinit(context);
-        signal_cyw43_task();
+#if CYW43_LWIP
-    }
+    lwip_freertos_deinit(context);
-    gpio_set_irq_enabled(CYW43_PIN_WL_HOST_WAKE, GPIO_IRQ_LEVEL_HIGH, false);
+#endif
-    gpio_remove_raw_irq_handler(CYW43_PIN_WL_HOST_WAKE, gpio_irq_handler);
+    // if it is our context, then we de-init it.
-    cyw43_deinit(&cyw43_state);
+    if (context == &cyw43_async_context_freertos.core) {
-}
+        async_context_deinit(context);
-
+        cyw43_arch_set_async_context(NULL);
-void cyw43_post_poll_hook(void) {
-    assert(cyw43_core_num == get_core_num());
-    gpio_set_irq_enabled(CYW43_PIN_WL_HOST_WAKE, GPIO_IRQ_LEVEL_HIGH, true);
-}
-
-// This is called in the gpio and low_prio_irq interrupts and on either core
-static void signal_cyw43_task(void) {
-    if (cyw43_task_handle) {
-        if (portCHECK_IF_IN_ISR()) {
-            vTaskNotifyGiveFromISR(cyw43_task_handle, NULL);
-        } else {
-            xTaskNotifyGive(cyw43_task_handle);
-        }
     }
 }
 
-void cyw43_schedule_internal_poll_dispatch(void (*func)(void)) {
-    assert(func == cyw43_poll);
-    signal_cyw43_task();
-}
-
-static int nesting;
-// Prevent background processing in pensv and access by the other core
-// These methods are called in pensv context and on either core
-// They can be called recursively
-void cyw43_thread_enter(void) {
-    // Lock the other core and stop low_prio_irq running
-    assert(!portCHECK_IF_IN_ISR());
-#if LWIP_TCPIP_CORE_LOCKING_INPUT
-    // we must share their mutex otherwise we can get deadlocks with two different recursive mutexes
-    LOCK_TCPIP_CORE();
-#else
-    xSemaphoreTakeRecursive(cyw43_mutex, portMAX_DELAY);
-#endif
-    nesting++;
-}
-
-#ifndef NDEBUG
-void cyw43_thread_lock_check(void) {
-    // Lock the other core and stop low_prio_irq running
-#if LWIP_TCPIP_CORE_LOCKING_INPUT
-    assert(xSemaphoreGetMutexHolder(lock_tcpip_core.mut) == xTaskGetCurrentTaskHandle());
-#else
-    assert(xSemaphoreGetMutexHolder(cyw43_mutex) == xTaskGetCurrentTaskHandle());
-#endif
-}
-#endif
-
-// Re-enable background processing
-void cyw43_thread_exit(void) {
-    // Run low_prio_irq if needed
-    --nesting;
-#if LWIP_TCPIP_CORE_LOCKING_INPUT
-    // we must share their mutex otherwise we can get deadlocks with two different recursive mutexes
-    UNLOCK_TCPIP_CORE();
-#else
-    xSemaphoreGiveRecursive(cyw43_mutex);
-#endif
-
-    if (!nesting && cyw43_task_handle != xTaskGetCurrentTaskHandle())
-        signal_cyw43_task();
-}
-
-void cyw43_delay_ms(uint32_t ms) {
-    assert(!portCHECK_IF_IN_ISR());
-    vTaskDelay(pdMS_TO_TICKS(ms));
-}
-
-void cyw43_delay_us(uint32_t us) {
-    if (us >= 1000) {
-        cyw43_delay_ms(us / 1000);
-    } else {
-        vTaskDelay(1);
-    }
-}
-
-void cyw43_arch_poll() {
-}
-
 #endif

src/rp2_common/pico_cyw43_arch/cyw43_arch_poll.c

@@ -4,110 +4,62 @@
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
-#include <stdio.h>
-#include "hardware/gpio.h"
-#include "hardware/irq.h"
-#include "pico/sem.h"
 #include "pico/cyw43_arch.h"
-#include "cyw43_stats.h"
+#include "pico/cyw43_driver.h"
 
 #if PICO_CYW43_ARCH_POLL
-#include <lwip/init.h>
+#include "pico/async_context_poll.h"
-#include "lwip/timeouts.h"
+#if CYW43_LWIP
+#include "pico/lwip_nosys.h"
+#endif
 
 #if CYW43_LWIP && !NO_SYS
 #error PICO_CYW43_ARCH_POLL requires lwIP NO_SYS=1
 #endif
 
-#define CYW43_GPIO_IRQ_HANDLER_PRIORITY 0x40
+static async_context_poll_t cyw43_async_context_poll;
 
-#ifndef NDEBUG
+async_context_t *cyw43_arch_init_default_async_context(void) {
-uint8_t cyw43_core_num;
+    if (async_context_poll_init_with_defaults(&cyw43_async_context_poll))
-#endif
+        return &cyw43_async_context_poll.core;
-
+    return NULL;
-bool cyw43_poll_required;
-
-// GPIO interrupt handler to tell us there's cyw43 has work to do
-static void gpio_irq_handler(void)
-{
-    uint32_t events = gpio_get_irq_event_mask(CYW43_PIN_WL_HOST_WAKE);
-    if (events & GPIO_IRQ_LEVEL_HIGH) {
-        // As we use a high level interrupt, it will go off forever until it's serviced
-        // So disable the interrupt until this is done. It's re-enabled again by CYW43_POST_POLL_HOOK
-        // which is called at the end of cyw43_poll_func
-        gpio_set_irq_enabled(CYW43_PIN_WL_HOST_WAKE, GPIO_IRQ_LEVEL_HIGH, false);
-        // also clear the force bit which we use to programmatically cause this handler to fire (on the right core)
-        io_irq_ctrl_hw_t *irq_ctrl_base = get_core_num() ?
-                                          &iobank0_hw->proc1_irq_ctrl : &iobank0_hw->proc0_irq_ctrl;
-        hw_clear_bits(&irq_ctrl_base->intf[CYW43_PIN_WL_HOST_WAKE/8], GPIO_IRQ_LEVEL_HIGH << (4 * (CYW43_PIN_WL_HOST_WAKE & 7)));
-        cyw43_schedule_internal_poll_dispatch(cyw43_poll);
-        CYW43_STAT_INC(IRQ_COUNT);
-    }
-}
-
-void cyw43_post_poll_hook(void) {
-    gpio_set_irq_enabled(CYW43_PIN_WL_HOST_WAKE, GPIO_IRQ_LEVEL_HIGH, true);
 }
 
 int cyw43_arch_init(void) {
-#ifndef NDEBUG
+    async_context_t *context = cyw43_arch_async_context();
-    cyw43_core_num = (uint8_t)get_core_num();
+    if (!context) {
-#endif
+        context = cyw43_arch_init_default_async_context();
-    cyw43_init(&cyw43_state);
+        if (!context) return PICO_ERROR_GENERIC;
-    static bool done_lwip_init;
+        cyw43_arch_set_async_context(context);
-    if (!done_lwip_init) {
-        lwip_init();
-        done_lwip_init = true;
     }
-    gpio_add_raw_irq_handler_with_order_priority(CYW43_PIN_WL_HOST_WAKE, gpio_irq_handler, CYW43_GPIO_IRQ_HANDLER_PRIORITY);
+    bool ok = cyw43_driver_init(context);
-    gpio_set_irq_enabled(CYW43_PIN_WL_HOST_WAKE, GPIO_IRQ_LEVEL_HIGH, true);
+#if CYW43_LWIP
-    irq_set_enabled(IO_IRQ_BANK0, true);
+    ok &= lwip_nosys_init(context);
+#endif
+    if (!ok) {
+        cyw43_arch_deinit();
+        return PICO_ERROR_GENERIC;
+    } else {
         return 0;
+    }
 }
 
 void cyw43_arch_deinit(void) {
-    gpio_set_irq_enabled(CYW43_PIN_WL_HOST_WAKE, GPIO_IRQ_LEVEL_HIGH, false);
+    async_context_t *context = cyw43_arch_async_context();
-    gpio_remove_raw_irq_handler(CYW43_PIN_WL_HOST_WAKE, gpio_irq_handler);
+    // there is a bit of a circular dependency here between lwIP and cyw43_driver. We
-    cyw43_deinit(&cyw43_state);
+    // shut down cyw43_driver first as it has IRQs calling back into lwIP. Also lwIP itself
-}
+    // does not actually get shut down.
-
+    // todo add a "pause" method to async_context if we need to provide some atomicity (we
-
+    //      don't want to take the lock as these methods may invoke execute_sync()
-void cyw43_schedule_internal_poll_dispatch(__unused void (*func)(void)) {
+    cyw43_driver_deinit(context);
-    cyw43_poll_required = true;
+#if CYW43_LWIP
-}
+    lwip_nosys_deinit(context);
-
-void cyw43_arch_poll(void)
-{
-    CYW43_STAT_INC(LWIP_RUN_COUNT);
-    sys_check_timeouts();
-    if (cyw43_poll) {
-        if (cyw43_sleep > 0) {
-            // todo check this; but we don't want to advance too quickly
-            static absolute_time_t last_poll_time;
-            absolute_time_t current = get_absolute_time();
-            if (absolute_time_diff_us(last_poll_time, current) > 1000) {
-                if (--cyw43_sleep == 0) {
-                    cyw43_poll_required = 1;
-                }
-                last_poll_time = current;
-            }
-        }
-        // todo graham i removed this because otherwise polling can do nothing during connect.
-        //  in the polling only case, the caller is responsible for throttling how often they call anyway.
-        //  The alternative would be to have the call to this function from the init set the poll_required flag first
-//        if (cyw43_poll_required) {
-            cyw43_poll();
-//            cyw43_poll_required = false;
-//        }
-    }
-}
-
-#ifndef NDEBUG
-void cyw43_thread_check() {
-    if (__get_current_exception() || get_core_num() != cyw43_core_num) {
-        panic("cyw43_thread_lock_check failed");
-    }
-}
 #endif
+    // if it is our context, then we de-init it.
+    if (context == &cyw43_async_context_poll.core) {
+        async_context_deinit(context);
+        cyw43_arch_set_async_context(NULL);
+    }
+}
 
 #endif

src/rp2_common/pico_cyw43_arch/cyw43_arch_threadsafe_background.c

@@ -4,317 +4,68 @@
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
-#include <stdio.h>
-
-#include "pico/cyw43_arch.h"
-#include "pico/mutex.h"
-#include "pico/sem.h"
-
-#include "hardware/gpio.h"
-#include "hardware/irq.h"
-
-#include "cyw43_stats.h"
-
-#if CYW43_LWIP
-#include <lwip/init.h>
-#include "lwip/timeouts.h"
-#endif
-
-// note same code
 #if PICO_CYW43_ARCH_THREADSAFE_BACKGROUND
 
-#if PICO_CYW43_ARCH_THREADSAFE_BACKGROUND && CYW43_LWIP && !NO_SYS
+#include "pico/cyw43_arch.h"
+#include "pico/cyw43_driver.h"
+#include "pico/async_context_threadsafe_background.h"
+
+#if CYW43_LWIP
+#include "pico/lwip_nosys.h"
+#endif
+
+#if CYW43_LWIP && !NO_SYS
 #error PICO_CYW43_ARCH_THREADSAFE_BACKGROUND requires lwIP NO_SYS=1
 #endif
-#if PICO_CYW43_ARCH_THREADSAFE_BACKGROUND && CYW43_LWIP && MEM_LIBC_MALLOC
+#if CYW43_LWIP && MEM_LIBC_MALLOC
+// would attempt to use malloc from IRQ context
 #error MEM_LIBC_MALLOC is incompatible with PICO_CYW43_ARCH_THREADSAFE_BACKGROUND
 #endif
-// todo right now we are now always doing a cyw43_dispatch along with a lwip one when hopping cores in low_prio_irq_schedule_dispatch
 
-#ifndef CYW43_SLEEP_CHECK_MS
+static async_context_threadsafe_background_t cyw43_async_context_threadsafe_background;
-#define CYW43_SLEEP_CHECK_MS 50 // How often to run lwip callback
-#endif
-static alarm_id_t periodic_alarm = -1;
 
-static inline uint recursive_mutex_enter_count(recursive_mutex_t *mutex) {
+async_context_t *cyw43_arch_init_default_async_context(void) {
-    return mutex->enter_count;
+    async_context_threadsafe_background_config_t config = async_context_threadsafe_background_default_config();
-}
+    if (async_context_threadsafe_background_init(&cyw43_async_context_threadsafe_background, &config))
-
+        return &cyw43_async_context_threadsafe_background.core;
-static inline lock_owner_id_t recursive_mutex_owner(recursive_mutex_t *mutex) {
+    return NULL;
-    return mutex->owner;
-}
-
-#define CYW43_GPIO_IRQ_HANDLER_PRIORITY 0x40
-
-enum {
-    CYW43_DISPATCH_SLOT_CYW43 = 0,
-    CYW43_DISPATCH_SLOT_ADAPTER,
-    CYW43_DISPATCH_SLOT_ENUM_COUNT
-};
-#ifndef CYW43_DISPATCH_SLOT_COUNT
-#define CYW43_DISPATCH_SLOT_COUNT CYW43_DISPATCH_SLOT_ENUM_COUNT
-#endif
-
-typedef void (*low_prio_irq_dispatch_t)(void);
-static void low_prio_irq_schedule_dispatch(size_t slot, low_prio_irq_dispatch_t f);
-
-static uint8_t cyw43_core_num;
-#ifndef NDEBUG
-static bool in_low_priority_irq;
-#endif
-static uint8_t low_priority_irq_num;
-static bool low_priority_irq_missed;
-static low_prio_irq_dispatch_t low_priority_irq_dispatch_slots[CYW43_DISPATCH_SLOT_COUNT];
-static recursive_mutex_t cyw43_mutex;
-semaphore_t cyw43_irq_sem;
-
-// Called in low priority pendsv interrupt only to do lwip processing and check cyw43 sleep
-static void periodic_worker(void)
-{
-#if CYW43_USE_STATS
-    static uint32_t counter;
-    if (counter++ % (30000 / LWIP_SYS_CHECK_MS) == 0) {
-        cyw43_dump_stats();
-    }
-#endif
-
-    CYW43_STAT_INC(LWIP_RUN_COUNT);
-#if CYW43_LWIP
-    sys_check_timeouts();
-#endif
-    if (cyw43_poll) {
-        if (cyw43_sleep > 0) {
-            if (--cyw43_sleep == 0) {
-                low_prio_irq_schedule_dispatch(CYW43_DISPATCH_SLOT_CYW43, cyw43_poll);
-            }
-        }
-    }
-}
-
-// Regular callback to get lwip to check for timeouts
-static int64_t periodic_alarm_handler(__unused alarm_id_t id, __unused void *user_data)
-{
-    // Do lwip processing in low priority pendsv interrupt
-    low_prio_irq_schedule_dispatch(CYW43_DISPATCH_SLOT_ADAPTER, periodic_worker);
-    return CYW43_SLEEP_CHECK_MS * 1000;
-}
-
-void cyw43_await_background_or_timeout_us(uint32_t timeout_us) {
-    // if we are called from within an IRQ, then don't wait (we are only ever called in a polling loop)
-    if (!__get_current_exception()) {
-        sem_acquire_timeout_us(&cyw43_irq_sem, timeout_us);
-    }
-}
-
-// GPIO interrupt handler to tell us there's cyw43 has work to do
-static void gpio_irq_handler(void)
-{
-    uint32_t events = gpio_get_irq_event_mask(CYW43_PIN_WL_HOST_WAKE);
-    if (events & GPIO_IRQ_LEVEL_HIGH) {
-        // As we use a high level interrupt, it will go off forever until it's serviced
-        // So disable the interrupt until this is done. It's re-enabled again by CYW43_POST_POLL_HOOK
-        // which is called at the end of cyw43_poll_func
-        gpio_set_irq_enabled(CYW43_PIN_WL_HOST_WAKE, GPIO_IRQ_LEVEL_HIGH, false);
-        // also clear the force bit which we use to progratically cause this handler to fire (on the right core)
-        io_irq_ctrl_hw_t *irq_ctrl_base = get_core_num() ?
-                                          &iobank0_hw->proc1_irq_ctrl : &iobank0_hw->proc0_irq_ctrl;
-        hw_clear_bits(&irq_ctrl_base->intf[CYW43_PIN_WL_HOST_WAKE/8], GPIO_IRQ_LEVEL_HIGH << (4 * (CYW43_PIN_WL_HOST_WAKE & 7)));
-        low_prio_irq_schedule_dispatch(CYW43_DISPATCH_SLOT_CYW43, cyw43_poll);
-        CYW43_STAT_INC(IRQ_COUNT);
-    }
-}
-
-// Low priority interrupt handler to perform background processing
-static void low_priority_irq_handler(void) {
-    assert(cyw43_core_num == get_core_num());
-    if (recursive_mutex_try_enter(&cyw43_mutex, NULL)) {
-        if (recursive_mutex_enter_count(&cyw43_mutex) != 1) {
-            low_priority_irq_missed = true;
-            CYW43_STAT_INC(PENDSV_DISABLED_COUNT);
-        } else {
-            CYW43_STAT_INC(PENDSV_RUN_COUNT);
-#ifndef NDEBUG
-            in_low_priority_irq = true;
-#endif
-            for (size_t i = 0; i < count_of(low_priority_irq_dispatch_slots); i++) {
-                if (low_priority_irq_dispatch_slots[i] != NULL) {
-                    low_prio_irq_dispatch_t f = low_priority_irq_dispatch_slots[i];
-                    low_priority_irq_dispatch_slots[i] = NULL;
-                    f();
-                }
-            }
-#ifndef NDEBUG
-            in_low_priority_irq = false;
-#endif
-        }
-        recursive_mutex_exit(&cyw43_mutex);
-    } else {
-        CYW43_STAT_INC(PENDSV_DISABLED_COUNT);
-        low_priority_irq_missed = true;
-    }
-    sem_release(&cyw43_irq_sem);
-}
-
-static bool low_prio_irq_init(uint8_t priority) {
-    assert(get_core_num() == cyw43_core_num);
-    int irq = user_irq_claim_unused(false);
-    if (irq < 0) return false;
-    low_priority_irq_num = (uint8_t) irq;
-    irq_set_exclusive_handler(low_priority_irq_num, low_priority_irq_handler);
-    irq_set_enabled(low_priority_irq_num, true);
-    irq_set_priority(low_priority_irq_num, priority);
-    return true;
-}
-
-static void low_prio_irq_deinit(void) {
-    if (low_priority_irq_num > 0) {
-        irq_set_enabled(low_priority_irq_num, false);
-        irq_remove_handler(low_priority_irq_num, low_priority_irq_handler);
-        user_irq_unclaim(low_priority_irq_num);
-        low_priority_irq_num = 0;
-    }
 }
 
 int cyw43_arch_init(void) {
-    cyw43_core_num = get_core_num();
+    async_context_t *context = cyw43_arch_async_context();
-    recursive_mutex_init(&cyw43_mutex);
+    if (!context) {
-    cyw43_init(&cyw43_state);
+        context = cyw43_arch_init_default_async_context();
-    sem_init(&cyw43_irq_sem, 0, 1);
+        if (!context) return PICO_ERROR_GENERIC;
-
+        cyw43_arch_set_async_context(context);
-    // Start regular lwip callback to handle timeouts
-    periodic_alarm = add_alarm_in_us(CYW43_SLEEP_CHECK_MS * 1000, periodic_alarm_handler, NULL, true);
-    if (periodic_alarm < 0) {
-        return PICO_ERROR_GENERIC;
     }
-
+    bool ok = cyw43_driver_init(context);
-    gpio_add_raw_irq_handler_with_order_priority(CYW43_PIN_WL_HOST_WAKE, gpio_irq_handler, CYW43_GPIO_IRQ_HANDLER_PRIORITY);
-    gpio_set_irq_enabled(CYW43_PIN_WL_HOST_WAKE, GPIO_IRQ_LEVEL_HIGH, true);
-    irq_set_enabled(IO_IRQ_BANK0, true);
-
 #if CYW43_LWIP
-    lwip_init();
+    ok &= lwip_nosys_init(context);
 #endif
-    // start low priority handler (no background work is done before this)
-    bool ok = low_prio_irq_init(PICO_LOWEST_IRQ_PRIORITY);
     if (!ok) {
         cyw43_arch_deinit();
         return PICO_ERROR_GENERIC;
+    } else {
+        return 0;
     }
-    return PICO_OK;
 }
 
 void cyw43_arch_deinit(void) {
-    if (periodic_alarm >= 0) {
+    async_context_t *context = cyw43_arch_async_context();
-        cancel_alarm(periodic_alarm);
+    // there is a bit of a circular dependency here between lwIP and cyw43_driver. We
-        periodic_alarm = -1;
+    // shut down cyw43_driver first as it has IRQs calling back into lwIP. Also lwIP itself
-    }
+    // does not actually get shut down.
-    gpio_set_irq_enabled(CYW43_PIN_WL_HOST_WAKE, GPIO_IRQ_LEVEL_HIGH, false);
+    // todo add a "pause" method to async_context if we need to provide some atomicity (we
-    gpio_remove_raw_irq_handler(CYW43_PIN_WL_HOST_WAKE, gpio_irq_handler);
+    //      don't want to take the lock as these methods may invoke execute_sync()
-    low_prio_irq_deinit();
+    cyw43_driver_deinit(context);
-    cyw43_deinit(&cyw43_state);
+#if CYW43_LWIP
-}
+    lwip_nosys_deinit(context);
-
-void cyw43_post_poll_hook(void) {
-    gpio_set_irq_enabled(CYW43_PIN_WL_HOST_WAKE, GPIO_IRQ_LEVEL_HIGH, true);
-}
-
-// This is called in the gpio and low_prio_irq interrupts and on either core
-static void low_prio_irq_schedule_dispatch(size_t slot, low_prio_irq_dispatch_t f) {
-    assert(slot < count_of(low_priority_irq_dispatch_slots));
-    low_priority_irq_dispatch_slots[slot] = f;
-    if (cyw43_core_num == get_core_num()) {
-        //on same core, can dispatch directly
-        irq_set_pending(low_priority_irq_num);
-    } else {
-        // on wrong core, so force via GPIO IRQ which itself calls this method for the CYW43 slot.
-        // since the CYW43 slot always uses the same function, this is fine with the addition of an
-        // extra (but harmless) CYW43 slot call when another SLOT is invoked.
-        // We could do better, but would have to track why the IRQ was called.
-        io_irq_ctrl_hw_t *irq_ctrl_base = cyw43_core_num ?
-                                          &iobank0_hw->proc1_irq_ctrl : &iobank0_hw->proc0_irq_ctrl;
-        hw_set_bits(&irq_ctrl_base->intf[CYW43_PIN_WL_HOST_WAKE/8], GPIO_IRQ_LEVEL_HIGH << (4 * (CYW43_PIN_WL_HOST_WAKE & 7)));
-    }
-}
-
-void cyw43_schedule_internal_poll_dispatch(void (*func)(void)) {
-    low_prio_irq_schedule_dispatch(CYW43_DISPATCH_SLOT_CYW43, func);
-}
-
-// Prevent background processing in pensv and access by the other core
-// These methods are called in pensv context and on either core
-// They can be called recursively
-void cyw43_thread_enter(void) {
-    // Lock the other core and stop low_prio_irq running
-    recursive_mutex_enter_blocking(&cyw43_mutex);
-}
-
-#ifndef NDEBUG
-void cyw43_thread_lock_check(void) {
-    // Lock the other core and stop low_prio_irq running
-    if (recursive_mutex_enter_count(&cyw43_mutex) < 1 || recursive_mutex_owner(&cyw43_mutex) != lock_get_caller_owner_id()) {
-        panic("cyw43_thread_lock_check failed");
-    }
-}
 #endif
-
+    // if it is our context, then we de-init it.
-// Re-enable background processing
+    if (context == &cyw43_async_context_threadsafe_background.core) {
-void cyw43_thread_exit(void) {
+        async_context_deinit(context);
-    // Run low_prio_irq if needed
+        cyw43_arch_set_async_context(NULL);
-    if (1 == recursive_mutex_enter_count(&cyw43_mutex)) {
-        // note the outer release of the mutex is not via cyw43_exit in the low_priority_irq case (it is a direct mutex exit)
-        assert(!in_low_priority_irq);
-//        if (low_priority_irq_missed) {
-//            low_priority_irq_missed = false;
-            if (low_priority_irq_dispatch_slots[CYW43_DISPATCH_SLOT_CYW43]) {
-                low_prio_irq_schedule_dispatch(CYW43_DISPATCH_SLOT_CYW43, cyw43_poll);
-            }
-//        }
-    }
-    recursive_mutex_exit(&cyw43_mutex);
-}
-
-
-static void cyw43_delay_until(absolute_time_t until) {
-    // sleep can be called in IRQs, so there's not much we can do there
-    if (__get_current_exception()) {
-        busy_wait_until(until);
-    } else {
-        sleep_until(until);
     }
 }
 
-void cyw43_delay_ms(uint32_t ms) {
-    cyw43_delay_until(make_timeout_time_ms(ms));
-}
-
-void cyw43_delay_us(uint32_t us) {
-    cyw43_delay_until(make_timeout_time_us(us));
-}
-
-void cyw43_arch_poll() {
-    // should not be necessary
-//    if (cyw43_poll) {
-//        low_prio_irq_schedule_dispatch(CYW43_DISPATCH_SLOT_CYW43, cyw43_poll);
-//    }
-}
-
-#if !CYW43_LWIP
-static void no_lwip_fail() {
-    panic("You cannot use IP with pico_cyw43_arch_none");
-}
-void cyw43_cb_tcpip_init(cyw43_t *self, int itf) {
-}
-void cyw43_cb_tcpip_deinit(cyw43_t *self, int itf) {
-}
-void cyw43_cb_tcpip_set_link_up(cyw43_t *self, int itf) {
-    no_lwip_fail();
-}
-void cyw43_cb_tcpip_set_link_down(cyw43_t *self, int itf) {
-    no_lwip_fail();
-}
-void cyw43_cb_process_ethernet(void *cb_data, int itf, size_t len, const uint8_t *buf) {
-    no_lwip_fail();
-}
-#endif
-
 #endif

src/rp2_common/pico_cyw43_arch/include/pico/cyw43_arch.h

@@ -104,12 +104,12 @@ extern "C" {
 #define PARAM_ASSERTIONS_ENABLED_CYW43_ARCH 0
 #endif
 
-// PICO_CONFIG: CYW43_ARCH_DEBUG_ENABLED, Enable/disable some debugging output in the pico_cyw43_arch module, type=bool, default=1 in debug builds, group=pico_cyw43_arch
+// PICO_CONFIG: PICO_CYW43_ARCH_DEBUG_ENABLED, Enable/disable some debugging output in the pico_cyw43_arch module, type=bool, default=1 in debug builds, group=pico_cyw43_arch
-#ifndef CYW43_ARCH_DEBUG_ENABLED
+#ifndef PICO_CYW43_ARCH_DEBUG_ENABLED
 #ifndef NDEBUG
-#define CYW43_ARCH_DEBUG_ENABLED 1
+#define PICO_CYW43_ARCH_DEBUG_ENABLED 1
 #else
-#define CYW43_ARCH_DEBUG_ENABLED 0
+#define PICO_CYW43_ARCH_DEBUG_ENABLED 0
 #endif
 #endif
 
@@ -129,6 +129,11 @@ extern "C" {
  * \note this method initializes wireless with a country code of \c PICO_CYW43_ARCH_DEFAULT_COUNTRY_CODE
  * which defaults to \c CYW43_COUNTRY_WORLDWIDE. Worldwide settings may not give the best performance; consider
  * setting PICO_CYW43_ARCH_DEFAULT_COUNTRY_CODE to a different value or calling \ref cyw43_arch_init_with_country
+ *
+ * By default this method initializes the cyw43_arch code's own \ref async_context by calling
+ * \ref cyw43_arch_init_default_async_context, however the user can specify use of their own async_context
+ * by calling \ref cyw43_arch_set_async_context() before calling this method
+ *
  * \return 0 if the initialization is successful, an error code otherwise \see pico_error_codes
  */
 int cyw43_arch_init(void);
@@ -141,31 +146,15 @@ int cyw43_arch_init(void);
  * was enabled at build time). This method must be called prior to using any other \c pico_cyw43_arch,
  * \c cyw43_driver or lwIP functions.
  *
+ * By default this method initializes the cyw43_arch code's own \ref async_context by calling
+ * \ref cyw43_arch_init_default_async_context, however the user can specify use of their own async_context
+ * by calling \ref cyw43_arch_set_async_context() before calling this method
+ *
  * \param country the country code to use (see \ref CYW43_COUNTRY_)
  * \return 0 if the initialization is successful, an error code otherwise \see pico_error_codes
  */
 int cyw43_arch_init_with_country(uint32_t country);
 
-/*!
- * \brief Enables Wi-Fi STA (Station) mode.
- * \ingroup pico_cyw43_arch
- *
- * This enables the Wi-Fi in \em Station mode such that connections can be made to other Wi-Fi Access Points
- */
-void cyw43_arch_enable_sta_mode(void);
-
-/*!
- * \brief Enables Wi-Fi AP (Access point) mode.
- * \ingroup pico_cyw43_arch
- *
- * This enables the Wi-Fi in \em Access \em Point mode such that connections can be made to the device by  other Wi-Fi clients
- * \param ssid the name for the access point
- * \param password the password to use or NULL for no password.
- * \param auth the authorization type to use when the password is enabled. Values are \ref CYW43_AUTH_WPA_TKIP_PSK,
- *             \ref CYW43_AUTH_WPA2_AES_PSK, or \ref CYW43_AUTH_WPA2_MIXED_PSK (see \ref CYW43_AUTH_)
- */
-void cyw43_arch_enable_ap_mode(const char *ssid, const char *password, uint32_t auth);
-
 /*!
  * \brief De-initialize the CYW43 architecture
  * \ingroup pico_cyw43_arch
@@ -173,80 +162,41 @@ void cyw43_arch_enable_ap_mode(const char *ssid, const char *password, uint32_t
  * This method de-initializes the `cyw43_driver` code and de-initializes the lwIP stack (if it
  * was enabled at build time). Note this method should always be called from the same core (or RTOS
  * task, depending on the environment) as \ref cyw43_arch_init.
+ *
+ * Additionally if the cyw43_arch is using its own async_context instance, then that instance is de-initialized.
  */
 void cyw43_arch_deinit(void);
 
 /*!
- * \brief Attempt to connect to a wireless access point, blocking until the network is joined or a failure is detected.
+ * \brief Return the current async_context currently in use by the cyw43_arch code
  * \ingroup pico_cyw43_arch
  *
- * \param ssid the network name to connect to
+ * \return the async_context.
- * \param pw the network password or NULL if there is no password required
- * \param auth the authorization type to use when the password is enabled. Values are \ref CYW43_AUTH_WPA_TKIP_PSK,
- *             \ref CYW43_AUTH_WPA2_AES_PSK, or \ref CYW43_AUTH_WPA2_MIXED_PSK (see \ref CYW43_AUTH_)
- *
- * \return 0 if the initialization is successful, an error code otherwise \see pico_error_codes
  */
-int cyw43_arch_wifi_connect_blocking(const char *ssid, const char *pw, uint32_t auth);
+async_context_t *cyw43_arch_async_context(void);
 
 /*!
- * \brief Attempt to connect to a wireless access point, blocking until the network is joined, a failure is detected or a timeout occurs
+ * \brief Set the async_context to be used by the cyw43_arch_init
  * \ingroup pico_cyw43_arch
  *
- * \param ssid the network name to connect to
+ * \note This method must be called before calling cyw43_arch_init or cyw43_arch_init_with_country
- * \param pw the network password or NULL if there is no password required
+ * if you wish to use a custom async_context instance.
- * \param auth the authorization type to use when the password is enabled. Values are \ref CYW43_AUTH_WPA_TKIP_PSK,
- *             \ref CYW43_AUTH_WPA2_AES_PSK, or \ref CYW43_AUTH_WPA2_MIXED_PSK (see \ref CYW43_AUTH_)
  *
- * \return 0 if the initialization is successful, an error code otherwise \see pico_error_codes
+ * \param context the async_context to be used
  */
-int cyw43_arch_wifi_connect_timeout_ms(const char *ssid, const char *pw, uint32_t auth, uint32_t timeout_ms);
+void cyw43_arch_set_async_context(async_context_t *context);
 
 /*!
- * \brief Start attempting to connect to a wireless access point
+ * \brief Initialize the default \ref async_context for the current cyw43_arch type
  * \ingroup pico_cyw43_arch
  *
- * This method tells the CYW43 driver to start connecting to an access point. You should subsequently check the
+ * This method initializes and returns a pointer to the static async_context associated
- * status by calling \ref cyw43_wifi_link_status.
+ * with cyw43_arch. This method is called by \ref cyw43_arch_init automatically
+ * if a different async_context has not been set by \ref cyw43_arch_set_async_context
  *
- * \param ssid the network name to connect to
+ * \return the context or NULL if initialization failed.
- * \param pw the network password or NULL if there is no password required
- * \param auth the authorization type to use when the password is enabled. Values are \ref CYW43_AUTH_WPA_TKIP_PSK,
- *             \ref CYW43_AUTH_WPA2_AES_PSK, or \ref CYW43_AUTH_WPA2_MIXED_PSK (see \ref CYW43_AUTH_)
- *
- * \return 0 if the scan was started successfully, an error code otherwise \see pico_error_codes
  */
-int cyw43_arch_wifi_connect_async(const char *ssid, const char *pw, uint32_t auth);
+async_context_t *cyw43_arch_init_default_async_context(void);
-
-/*!
- * \brief Return the country code used to initialize cyw43_arch
- * \ingroup pico_cyw43_arch
- *
- * \return the country code (see \ref CYW43_COUNTRY_)
- */
-uint32_t cyw43_arch_get_country_code(void);
-
-/*!
- * \brief Set a GPIO pin on the wireless chip to a given value
- * \ingroup pico_cyw43_arch
- * \note this method does not check for errors setting the GPIO. You can use the lower level \ref cyw43_gpio_set instead if you wish
- * to check for errors.
- *
- * \param wl_gpio the GPIO number on the wireless chip
- * \param value true to set the GPIO, false to clear it.
- */
-void cyw43_arch_gpio_put(uint wl_gpio, bool value);
-
-/*!
- * \brief Read the value of a GPIO pin on the wireless chip
- * \ingroup pico_cyw43_arch
- * \note this method does not check for errors setting the GPIO. You can use the lower level \ref cyw43_gpio_get instead if you wish
- * to check for errors.
- *
- * \param wl_gpio the GPIO number on the wireless chip
- * \return true if the GPIO is high, false otherwise
- */
-bool cyw43_arch_gpio_get(uint wl_gpio);
 
 /*!
  * \brief Perform any processing required by the \c cyw43_driver or the TCP/IP stack
@@ -258,6 +208,18 @@ bool cyw43_arch_gpio_get(uint wl_gpio);
  */
 void cyw43_arch_poll(void);
 
+/*!
+ * \brief Sleep until there is cyw43_driver work to be done
+ * \ingroup pico_cyw43_arch
+ *
+ * This method may be called by code that is waiting for an event to
+ * come from the cyw43_driver, and has no work to do, but would like
+ * to sleep without blocking any background work associated with the cyw43_driver.
+ *
+ * \param until the time to wait until if there is no work to do.
+ */
+void cyw43_arch_wait_for_work_until(absolute_time_t until);
+
 /*!
  * \fn cyw43_arch_lwip_begin
  * \brief Acquire any locks required to call into lwIP
@@ -321,6 +283,98 @@ void cyw43_arch_poll(void);
  * \sa cyw43_arch_lwip_protect
  */
 
+/*!
+ * \brief Return the country code used to initialize cyw43_arch
+ * \ingroup pico_cyw43_arch
+ *
+ * \return the country code (see \ref CYW43_COUNTRY_)
+ */
+uint32_t cyw43_arch_get_country_code(void);
+
+/*!
+ * \brief Enables Wi-Fi STA (Station) mode.
+ * \ingroup pico_cyw43_arch
+ *
+ * This enables the Wi-Fi in \emStation mode such that connections can be made to other Wi-Fi Access Points
+ */
+void cyw43_arch_enable_sta_mode(void);
+
+/*!
+ * \brief Enables Wi-Fi AP (Access point) mode.
+ * \ingroup pico_cyw43_arch
+ *
+ * This enables the Wi-Fi in \em Access \em Point mode such that connections can be made to the device by  other Wi-Fi clients
+ * \param ssid the name for the access point
+ * \param password the password to use or NULL for no password.
+ * \param auth the authorization type to use when the password is enabled. Values are \ref CYW43_AUTH_WPA_TKIP_PSK,
+ *             \ref CYW43_AUTH_WPA2_AES_PSK, or \ref CYW43_AUTH_WPA2_MIXED_PSK (see \ref CYW43_AUTH_)
+ */
+void cyw43_arch_enable_ap_mode(const char *ssid, const char *password, uint32_t auth);
+
+/*!
+ * \brief Attempt to connect to a wireless access point, blocking until the network is joined or a failure is detected.
+ * \ingroup pico_cyw43_arch
+ *
+ * \param ssid the network name to connect to
+ * \param pw the network password or NULL if there is no password required
+ * \param auth the authorization type to use when the password is enabled. Values are \ref CYW43_AUTH_WPA_TKIP_PSK,
+ *             \ref CYW43_AUTH_WPA2_AES_PSK, or \ref CYW43_AUTH_WPA2_MIXED_PSK (see \ref CYW43_AUTH_)
+ *
+ * \return 0 if the initialization is successful, an error code otherwise \see pico_error_codes
+ */
+int cyw43_arch_wifi_connect_blocking(const char *ssid, const char *pw, uint32_t auth);
+
+/*!
+ * \brief Attempt to connect to a wireless access point, blocking until the network is joined, a failure is detected or a timeout occurs
+ * \ingroup pico_cyw43_arch
+ *
+ * \param ssid the network name to connect to
+ * \param pw the network password or NULL if there is no password required
+ * \param auth the authorization type to use when the password is enabled. Values are \ref CYW43_AUTH_WPA_TKIP_PSK,
+ *             \ref CYW43_AUTH_WPA2_AES_PSK, or \ref CYW43_AUTH_WPA2_MIXED_PSK (see \ref CYW43_AUTH_)
+ *
+ * \return 0 if the initialization is successful, an error code otherwise \see pico_error_codes
+ */
+int cyw43_arch_wifi_connect_timeout_ms(const char *ssid, const char *pw, uint32_t auth, uint32_t timeout);
+
+/*!
+ * \brief Start attempting to connect to a wireless access point
+ * \ingroup pico_cyw43_arch
+ *
+ * This method tells the CYW43 driver to start connecting to an access point. You should subsequently check the
+ * status by calling \ref cyw43_wifi_link_status.
+ *
+ * \param ssid the network name to connect to
+ * \param pw the network password or NULL if there is no password required
+ * \param auth the authorization type to use when the password is enabled. Values are \ref CYW43_AUTH_WPA_TKIP_PSK,
+ *             \ref CYW43_AUTH_WPA2_AES_PSK, or \ref CYW43_AUTH_WPA2_MIXED_PSK (see \ref CYW43_AUTH_)
+ *
+ * \return 0 if the scan was started successfully, an error code otherwise \see pico_error_codes
+ */
+int cyw43_arch_wifi_connect_async(const char *ssid, const char *pw, uint32_t auth);
+
+/*!
+ * \brief Set a GPIO pin on the wireless chip to a given value
+ * \ingroup pico_cyw43_arch
+ * \note this method does not check for errors setting the GPIO. You can use the lower level \ref cyw43_gpio_set instead if you wish
+ * to check for errors.
+ *
+ * \param wl_gpio the GPIO number on the wireless chip
+ * \param value true to set the GPIO, false to clear it.
+ */
+void cyw43_arch_gpio_put(uint wl_gpio, bool value);
+
+/*!
+ * \brief Read the value of a GPIO pin on the wireless chip
+ * \ingroup pico_cyw43_arch
+ * \note this method does not check for errors setting the GPIO. You can use the lower level \ref cyw43_gpio_get instead if you wish
+ * to check for errors.
+ *
+ * \param wl_gpio the GPIO number on the wireless chip
+ * \return true if the GPIO is high, false otherwise
+ */
+bool cyw43_arch_gpio_get(uint wl_gpio);
+
 #ifdef __cplusplus
 }
 #endif

src/rp2_common/pico_cyw43_arch/include/pico/cyw43_arch/arch_common.h

@@ -11,6 +11,7 @@
 #include "pico/time.h"
 #include "hardware/gpio.h"
 #include "pico/error.h"
+#include "pico/async_context.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -66,6 +67,62 @@ void cyw43_hal_get_mac(int idx, uint8_t buf[6]);
 
 void cyw43_hal_generate_laa_mac(int idx, uint8_t buf[6]);
 
+
+void cyw43_thread_enter(void);
+void cyw43_thread_exit(void);
+
+#define CYW43_THREAD_ENTER cyw43_thread_enter();
+#define CYW43_THREAD_EXIT cyw43_thread_exit();
+#ifndef NDEBUG
+void cyw43_thread_lock_check(void);
+#define cyw43_arch_lwip_check() cyw43_thread_lock_check()
+#define CYW43_THREAD_LOCK_CHECK cyw43_arch_lwip_check();
+#else
+#define cyw43_arch_lwip_check() ((void)0)
+#define CYW43_THREAD_LOCK_CHECK
+#endif
+
+void cyw43_await_background_or_timeout_us(uint32_t timeout_us);
+// todo not 100% sure about the timeouts here; MP uses __WFI which will always wakeup periodically
+#define CYW43_SDPCM_SEND_COMMON_WAIT cyw43_await_background_or_timeout_us(1000);
+#define CYW43_DO_IOCTL_WAIT cyw43_await_background_or_timeout_us(1000);
+
+void cyw43_delay_ms(uint32_t ms);
+void cyw43_delay_us(uint32_t us);
+
+void cyw43_schedule_internal_poll_dispatch(void (*func)(void));
+
+void cyw43_post_poll_hook(void);
+#define CYW43_POST_POLL_HOOK cyw43_post_poll_hook();
+
+static inline void cyw43_arch_lwip_begin(void) {
+    cyw43_thread_enter();
+}
+
+static inline void cyw43_arch_lwip_end(void) {
+    cyw43_thread_exit();
+}
+
+static inline int cyw43_arch_lwip_protect(int (*func)(void *param), void *param) {
+    cyw43_arch_lwip_begin();
+    int rc = func(param);
+    cyw43_arch_lwip_end();
+    return rc;
+}
+
+#if CYW43_USE_BTSTACK
+static inline int cyw43_bt_init(void) { return 0; }
+static inline void cyw43_bt_deinit(void) {}
+
+static inline void cyw43_arch_btstack_begin(void) {
+    cyw43_thread_enter();
+}
+
+static inline void cyw43_arch_btstack_end(void) {
+    cyw43_thread_exit();
+}
+#endif
+
 #ifdef __cplusplus
 }
 #endif

src/rp2_common/pico_cyw43_arch/include/pico/cyw43_arch/arch_freertos.h

@@ -13,46 +13,15 @@
 extern "C" {
 #endif
 
-void cyw43_thread_enter(void);
+// PICO_CONFIG: CYW43_TASK_STACK_SIZE, Stack size for the CYW43 FreeRTOS task in 4-byte words, type=int, default=1024, group=pico_cyw43_arch
-void cyw43_thread_exit(void);
+#ifndef CYW43_TASK_STACK_SIZE
-
+#define CYW43_TASK_STACK_SIZE 1024
-#define CYW43_THREAD_ENTER cyw43_thread_enter();
-#define CYW43_THREAD_EXIT cyw43_thread_exit();
-#ifndef NDEBUG
-void cyw43_thread_lock_check(void);
-#define cyw43_arch_lwip_check() cyw43_thread_lock_check()
-#define CYW43_THREAD_LOCK_CHECK cyw43_arch_lwip_check();
-#else
-#define cyw43_arch_lwip_check() ((void)0)
-#define CYW43_THREAD_LOCK_CHECK
 #endif
 
-void cyw43_await_background_or_timeout_us(uint32_t timeout_us);
+// PICO_CONFIG: CYW43_TASK_PRIORITY, Priority for the CYW43 FreeRTOS task, type=int default=4, group=pico_cyw43_arch
-// todo not 100% sure about the timeouts here; MP uses __WFI which will always wakeup periodically
+#ifndef CYW43_TASK_PRIORITY
-#define CYW43_SDPCM_SEND_COMMON_WAIT cyw43_await_background_or_timeout_us(1000);
+#define CYW43_TASK_PRIORITY (tskIDLE_PRIORITY + 4)
-#define CYW43_DO_IOCTL_WAIT cyw43_await_background_or_timeout_us(1000);
+#endif
-
-void cyw43_delay_ms(uint32_t ms);
-void cyw43_delay_us(uint32_t us);
-
-void cyw43_schedule_internal_poll_dispatch(void (*func)(void));
-
-void cyw43_post_poll_hook(void);
-#define CYW43_POST_POLL_HOOK cyw43_post_poll_hook();
-
-static inline void cyw43_arch_lwip_begin(void) {
-    cyw43_thread_enter();
-}
-static inline void cyw43_arch_lwip_end(void) {
-    cyw43_thread_exit();
-}
-
-static inline int cyw43_arch_lwip_protect(int (*func)(void *param), void *param) {
-    cyw43_arch_lwip_begin();
-    int rc = func(param);
-    cyw43_arch_lwip_end();
-    return rc;
-}
 
 #ifdef __cplusplus
 }

src/rp2_common/pico_cyw43_arch/include/pico/cyw43_arch/arch_poll.h

@@ -15,42 +15,6 @@
 extern "C" {
 #endif
 
-#define CYW43_THREAD_ENTER
-#define CYW43_THREAD_EXIT
-#ifndef NDEBUG
-
-void cyw43_thread_check(void);
-
-#define cyw43_arch_lwip_check() cyw43_thread_check()
-#define CYW43_THREAD_LOCK_CHECK cyw43_arch_lwip_check();
-#else
-#define cyw43_arch_lwip_check() ((void)0)
-#define CYW43_THREAD_LOCK_CHECK
-#endif
-
-#define CYW43_SDPCM_SEND_COMMON_WAIT cyw43_poll_required = true;
-#define CYW43_DO_IOCTL_WAIT cyw43_poll_required = true;
-
-#define cyw43_delay_ms sleep_ms
-#define cyw43_delay_us sleep_us
-
-void cyw43_schedule_internal_poll_dispatch(void (*func)(void));
-
-void cyw43_post_poll_hook(void);
-
-extern bool cyw43_poll_required;
-
-#define CYW43_POST_POLL_HOOK cyw43_post_poll_hook();
-#endif
-
-#ifndef DOXYGEN_GENERATION // multiple definitions in separate headers seems to confused doxygen
-#define cyw43_arch_lwip_begin() ((void)0)
-#define cyw43_arch_lwip_end() ((void)0)
-
-static inline int cyw43_arch_lwip_protect(int (*func)(void *param), void *param) {
-    return func(param);
-}
-
 #ifdef __cplusplus
 }
 #endif

src/rp2_common/pico_cyw43_arch/include/pico/cyw43_arch/arch_threadsafe_background.h

@@ -13,53 +13,6 @@
 extern "C" {
 #endif
 
-void cyw43_thread_enter(void);
-
-void cyw43_thread_exit(void);
-
-#define CYW43_THREAD_ENTER cyw43_thread_enter();
-#define CYW43_THREAD_EXIT cyw43_thread_exit();
-#ifndef NDEBUG
-
-void cyw43_thread_lock_check(void);
-
-#define cyw43_arch_lwip_check() cyw43_thread_lock_check()
-#define CYW43_THREAD_LOCK_CHECK cyw43_arch_lwip_check();
-#else
-#define cyw43_arch_lwip_check() ((void)0)
-#define CYW43_THREAD_LOCK_CHECK
-#endif
-
-void cyw43_await_background_or_timeout_us(uint32_t timeout_us);
-// todo not 100% sure about the timeouts here; MP uses __WFI which will always wakeup periodically
-#define CYW43_SDPCM_SEND_COMMON_WAIT cyw43_await_background_or_timeout_us(1000);
-#define CYW43_DO_IOCTL_WAIT cyw43_await_background_or_timeout_us(1000);
-
-void cyw43_delay_ms(uint32_t ms);
-
-void cyw43_delay_us(uint32_t us);
-
-void cyw43_schedule_internal_poll_dispatch(void (*func)(void));
-
-void cyw43_post_poll_hook(void);
-
-#define CYW43_POST_POLL_HOOK cyw43_post_poll_hook();
-
-static inline void cyw43_arch_lwip_begin(void) {
-    cyw43_thread_enter();
-}
-
-static inline void cyw43_arch_lwip_end(void) {
-    cyw43_thread_exit();
-}
-
-static inline int cyw43_arch_lwip_protect(int (*func)(void *param), void *param) {
-    cyw43_arch_lwip_begin();
-    int rc = func(param);
-    cyw43_arch_lwip_end();
-    return rc;
-}
-
 #ifdef __cplusplus
 }
 #endif

src/rp2_common/pico_cyw43_driver/CMakeLists.txt

@@ -21,19 +21,24 @@ if (EXISTS ${PICO_CYW43_DRIVER_PATH}/${CYW43_DRIVER_TEST_FILE})
     pico_register_common_scope_var(PICO_CYW43_DRIVER_PATH)
 
     # base driver without our bus
-    add_library(cyw43_driver_base INTERFACE)
+    add_library(cyw43_driver INTERFACE)
-    target_sources(cyw43_driver_base INTERFACE
+    target_sources(cyw43_driver INTERFACE
             ${PICO_CYW43_DRIVER_PATH}/src/cyw43_ll.c
             ${PICO_CYW43_DRIVER_PATH}/src/cyw43_stats.c
             ${PICO_CYW43_DRIVER_PATH}/src/cyw43_lwip.c
             ${PICO_CYW43_DRIVER_PATH}/src/cyw43_ctrl.c
             )
-    target_include_directories(cyw43_driver_base INTERFACE
+    target_include_directories(cyw43_driver INTERFACE
             ${PICO_CYW43_DRIVER_PATH}/src
             ${PICO_CYW43_DRIVER_PATH}/firmware
             )
 
-    # Build the driver for cyw43 for pico w
+    # pico_cyw43_driver adds async_context integration to cyw43_driver
+    add_library(pico_cyw43_driver INTERFACE)
+    target_sources(pico_cyw43_driver INTERFACE
+            cyw43_driver.c)
+    target_include_directories(pico_cyw43_driver INTERFACE ${CMAKE_CURRENT_LIST_DIR}/include)
+    target_link_libraries(pico_cyw43_driver INTERFACE cyw43_driver)
 
     # Firmware stuff
     set(CYW43_FIRMWARE_BIN 43439A0-7.95.49.00.combined)
@@ -60,6 +65,7 @@ if (EXISTS ${PICO_CYW43_DRIVER_PATH}/${CYW43_DRIVER_TEST_FILE})
             ${CYW43_FIRMWARE_BIN} ${CYW43_FIRMWARE_OBJ}
             VERBATIM)
 
+    # cyw43_driver_picow is cyw43_driver plus Pico W specific bus implementation, and Pico W firmware
     add_library(cyw43_driver_picow INTERFACE)
     target_sources(cyw43_driver_picow INTERFACE
             ${CMAKE_CURRENT_LIST_DIR}/cyw43_bus_pio_spi.c
@@ -70,8 +76,7 @@ if (EXISTS ${PICO_CYW43_DRIVER_PATH}/${CYW43_DRIVER_TEST_FILE})
             ${CYW43_FIRMWARE_OBJ}
             )
     target_link_libraries(cyw43_driver_picow INTERFACE
-            cyw43_driver_base
+            cyw43_driver
-            pico_stdlib
             hardware_pio
             hardware_dma
             hardware_exception

src/rp2_common/pico_cyw43_driver/cyw43_driver.c

@@ -0,0 +1,122 @@
+/*
+ * Copyright (c) 2022 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include "hardware/gpio.h"
+#include "hardware/irq.h"
+#include "cyw43.h"
+#include "pico/cyw43_driver.h"
+
+#ifndef CYW43_GPIO_IRQ_HANDLER_PRIORITY
+#define CYW43_GPIO_IRQ_HANDLER_PRIORITY 0x40
+#endif
+
+#ifndef CYW43_SLEEP_CHECK_MS
+#define CYW43_SLEEP_CHECK_MS 50
+#endif
+
+static async_context_t *cyw43_async_context;
+
+static void cyw43_sleep_timeout_reached(async_context_t *context, async_at_time_worker_t *worker);
+static void cyw43_do_poll(async_context_t *context, async_when_pending_worker_t *worker);
+
+static async_at_time_worker_t sleep_timeout_worker = {
+        .do_work = cyw43_sleep_timeout_reached
+};
+
+static async_when_pending_worker_t cyw43_poll_worker = {
+        .do_work = cyw43_do_poll
+};
+
+static void cyw43_set_irq_enabled(bool enabled) {
+    gpio_set_irq_enabled(CYW43_PIN_WL_HOST_WAKE, GPIO_IRQ_LEVEL_HIGH, enabled);
+}
+
+// GPIO interrupt handler to tell us there's cyw43 has work to do
+static void cyw43_gpio_irq_handler(void)
+{
+    uint32_t events = gpio_get_irq_event_mask(CYW43_PIN_WL_HOST_WAKE);
+    if (events & GPIO_IRQ_LEVEL_HIGH) {
+        // As we use a high level interrupt, it will go off forever until it's serviced
+        // So disable the interrupt until this is done. It's re-enabled again by CYW43_POST_POLL_HOOK
+        // which is called at the end of cyw43_poll_func
+        cyw43_set_irq_enabled(false);
+        async_context_set_work_pending(cyw43_async_context, &cyw43_poll_worker);
+    }
+}
+
+uint32_t cyw43_irq_init(__unused void *param) {
+#ifndef NDEBUG
+    assert(get_core_num() == async_context_core_num(cyw43_async_context));
+#endif
+    gpio_add_raw_irq_handler_with_order_priority(CYW43_PIN_WL_HOST_WAKE, cyw43_gpio_irq_handler, CYW43_GPIO_IRQ_HANDLER_PRIORITY);
+    cyw43_set_irq_enabled(true);
+    irq_set_enabled(IO_IRQ_BANK0, true);
+    return 0;
+}
+
+uint32_t cyw43_irq_deinit(__unused void *param) {
+#ifndef NDEBUG
+    assert(get_core_num() == async_context_core_num(cyw43_async_context));
+#endif
+    gpio_remove_raw_irq_handler(CYW43_PIN_WL_HOST_WAKE, cyw43_gpio_irq_handler);
+    cyw43_set_irq_enabled(false);
+    return 0;
+}
+
+void cyw43_post_poll_hook(void) {
+#ifndef NDEBUG
+    assert(get_core_num() == async_context_core_num(cyw43_async_context));
+#endif
+    cyw43_set_irq_enabled(true);
+}
+
+void cyw43_schedule_internal_poll_dispatch(__unused void (*func)(void)) {
+    assert(func == cyw43_poll);
+    async_context_set_work_pending(cyw43_async_context, &cyw43_poll_worker);
+}
+
+static void cyw43_do_poll(async_context_t *context, __unused async_when_pending_worker_t *worker) {
+#ifndef NDEBUG
+    assert(get_core_num() == async_context_core_num(cyw43_async_context));
+#endif
+    if (cyw43_poll) {
+        if (cyw43_sleep > 0) {
+            cyw43_sleep--;
+        }
+        cyw43_poll();
+        if (cyw43_sleep) {
+            async_context_add_at_time_worker_in_ms(context, &sleep_timeout_worker, CYW43_SLEEP_CHECK_MS);
+        } else {
+            async_context_remove_at_time_worker(context, &sleep_timeout_worker);
+        }
+    }
+}
+
+static void cyw43_sleep_timeout_reached(async_context_t *context, async_at_time_worker_t *worker) {
+    assert(context == cyw43_async_context);
+    assert(worker == &sleep_timeout_worker);
+    async_context_set_work_pending(cyw43_async_context, &cyw43_poll_worker);
+}
+
+bool cyw43_driver_init(async_context_t *context) {
+    cyw43_init(&cyw43_state);
+    cyw43_async_context = context;
+    // we need the IRQ to be on the same core as the context, because we need to be able to enable/disable the IRQ
+    // from there later
+    async_context_execute_sync(context, cyw43_irq_init, NULL);
+    async_context_add_when_pending_worker(context, &cyw43_poll_worker);
+    return true;
+}
+
+void cyw43_driver_deinit(async_context_t *context) {
+    assert(context == cyw43_async_context);
+    async_context_remove_at_time_worker(context, &sleep_timeout_worker);
+    async_context_remove_when_pending_worker(context, &cyw43_poll_worker);
+    // the IRQ IS on the same core as the context, so must be de-initialized there
+    async_context_execute_sync(context, cyw43_irq_deinit, NULL);
+    cyw43_deinit(&cyw43_state);
+    cyw43_async_context = NULL;
+}

src/rp2_common/pico_cyw43_driver/include/pico/cyw43_driver.h

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2022 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef _PICO_CYW43_DRIVER_ASYNC_CONTEXT_H
+#define _PICO_CYW43_DRIVER_ASYNC_CONTEXT_H
+
+/** \file pico/cyw43_driver.h
+ *  \defgroup pico_cyw43_driver pico_cyw43_driver
+ *
+ * A wrapper around the lower level cyw43_driver, that integrates it with \ref pico_async_context
+ * for handling background work.
+ */
+
+#include "pico.h"
+#include "pico/async_context.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*! \brief Initializes the lower level cyw43_driver and integrates it with the provided async_context
+ *  \ingroup pico_cyw43_driver
+ *
+ *  If the initialization succeeds, \ref lwip_nosys_deinit() can be called to shutdown lwIP support
+ *
+ * \param context the async_context instance that provides the abstraction for handling asynchronous work.
+ * \return true if the initialization succeeded
+*/
+bool cyw43_driver_init(async_context_t *context);
+
+/*! \brief De-initialize the lowever level cyw43_driver and unhooks it from the async_context
+ *  \ingroup pico_cyw43_driver
+ *
+ * \param context the async_context the cyw43_driver support was added to via \ref cyw43_driver_init
+*/
+void cyw43_driver_deinit(async_context_t *context);
+
+#ifdef __cplusplus
+}
+#endif
+#endif

src/rp2_common/pico_lwip/CMakeLists.txt

@@ -6,10 +6,10 @@ endif ()
 set(LWIP_TEST_PATH "src/Filelists.cmake")
 if (NOT PICO_LWIP_PATH)
     set(PICO_LWIP_PATH ${PROJECT_SOURCE_DIR}/lib/lwip)
-#    if (NOT EXISTS ${PICO_LWIP_PATH}/${LWIP_TEST_PATH})
+    if (PICO_CYW43_SUPPORTED AND NOT EXISTS ${PICO_LWIP_PATH}/${LWIP_TEST_PATH})
-#        message(WARNING "LWIP submodule has not been initialized; Pico W wireless support will be unavailable
+        message(WARNING "LWIP submodule has not been initialized; Pico W wireless support will be unavailable
 #hint: try 'git submodule update --init' from your SDK directory (${PICO_SDK_PATH}).")
-#    endif()
+    endif()
 elseif (NOT EXISTS ${PICO_LWIP_PATH}/${LWIP_TEST_PATH})
     message(WARNING "PICO_LWIP_PATH specified but content not present.")
 endif()
@@ -46,7 +46,7 @@ if (EXISTS ${PICO_LWIP_PATH}/${LWIP_TEST_PATH})
             ${PICO_LWIP_PATH}/src/core/tcp_out.c
             ${PICO_LWIP_PATH}/src/core/timeouts.c
             ${PICO_LWIP_PATH}/src/core/udp.c
-            ${CMAKE_CURRENT_LIST_DIR}/random.c
+            ${CMAKE_CURRENT_LIST_DIR}/lwip_random.c
             )
     target_include_directories(pico_lwip_core INTERFACE
             ${PICO_LWIP_PATH}/src/include)
@@ -269,11 +269,12 @@ if (EXISTS ${PICO_LWIP_PATH}/${LWIP_TEST_PATH})
     # our nosys impl
     add_library(pico_lwip_nosys INTERFACE)
     target_sources(pico_lwip_nosys INTERFACE
-            ${CMAKE_CURRENT_LIST_DIR}/nosys.c
+            ${CMAKE_CURRENT_LIST_DIR}/lwip_nosys.c
             )
     target_link_libraries(pico_lwip_nosys INTERFACE
-            pico_lwip_arch)
+            pico_async_context_base
-
+            pico_lwip_arch
+            pico_lwip)
 
     if (NOT PICO_LWIP_CONTRIB_PATH)
         set(PICO_LWIP_CONTRIB_PATH ${PICO_LWIP_PATH}/contrib)
@@ -291,5 +292,14 @@ if (EXISTS ${PICO_LWIP_PATH}/${LWIP_TEST_PATH})
     target_link_libraries(pico_lwip_contrib_freertos INTERFACE
             pico_lwip_arch)
 
+    add_library(pico_lwip_freertos INTERFACE)
+    target_sources(pico_lwip_freertos INTERFACE
+            ${CMAKE_CURRENT_LIST_DIR}/lwip_freertos.c
+            )
+    target_link_libraries(pico_lwip_freertos INTERFACE
+            pico_async_context_base
+            pico_lwip
+            pico_lwip_contrib_freertos)
+
     pico_promote_common_scope_vars()
 endif()

src/rp2_common/pico_lwip/include/arch/cc.h

@@ -34,9 +34,18 @@
 
 #include <sys/time.h>
 
+#ifndef PICO_LWIP_CUSTOM_LOCK_TCPIP_CORE
+#define PICO_LWIP_CUSTOM_LOCK_TCPIP_CORE 1
+#endif
+
 #if NO_SYS
 // todo really we should just not allow SYS_LIGHTWEIGHT_PROT for nosys mode (it doesn't do anything anyway)
 typedef int sys_prot_t;
+#elif PICO_LWIP_CUSTOM_LOCK_TCPIP_CORE
+void pico_lwip_custom_lock_tcpip_core(void);
+void pico_lwip_custom_unlock_tcpip_core(void);
+#define LOCK_TCPIP_CORE() pico_lwip_custom_lock_tcpip_core()
+#define UNLOCK_TCPIP_CORE() pico_lwip_custom_unlock_tcpip_core()
 #endif
 
 /* define compiler specific symbols */
@@ -76,8 +85,14 @@ typedef int sys_prot_t;
 #define LWIP_PLATFORM_ASSERT(x) panic(x)
 #endif
 
-unsigned int pico_lwip_rand(void);
 #ifndef LWIP_RAND
+#ifdef __cplusplus
+extern "C" {
+#endif
+unsigned int pico_lwip_rand(void);
+#ifdef __cplusplus
+}
+#endif
 // Use ROSC based random number generation, more for the fact that rand() may not be seeded, than anything else
 #define LWIP_RAND pico_lwip_rand
 #endif

src/rp2_common/pico_lwip/include/pico/lwip_freertos.h

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2022 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef _PICO_LWIP_FREERTOS_H
+#define _PICO_LWIP_FREERTOS_H
+
+#include "pico.h"
+#include "pico/async_context.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*! \brief Initializes lwIP (NO_SYS=0 mode) support support for FreeRTOS using the provided async_context
+ *  \ingroup pico_lwip
+ *
+ * If the initialization succeeds, \ref lwip_freertos_deinit() can be called to shutdown lwIP support
+ *
+ * \param context the async_context instance that provides the abstraction for handling asynchronous work. Note in general
+ * this would be an \ref async_context_freertos instance, though it doesn't have to be.
+ *
+ * \return true if the initialization succeeded
+*/
+bool lwip_freertos_init(async_context_t *context);
+
+/*! \brief De-initialize lwIP (NO_SYS=0 mode) support for FreeRTOS
+ *  \ingroup pico_lwip
+ *
+ * Note that since lwIP may only be initialized once, and doesn't itself provide a shutdown mechanism, lwIP
+ * itself may still consume resources.
+ *
+ * It is however safe to call \ref lwip_freertos_init again later.
+ *
+ * \param context the async_context the lwip_freertos support was added to via \ref lwip_freertos_init
+*/
+void lwip_freertos_deinit(async_context_t *context);
+
+#ifdef __cplusplus
+}
+#endif
+#endif

src/rp2_common/pico_lwip/include/pico/lwip_nosys.h

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2022 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef _PICO_LWIP_NOSYS_H
+#define _PICO_LWIP_NOSYS_H
+
+#include "pico.h"
+#include "pico/async_context.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*! \brief Initializes lwIP (NO_SYS=1 mode) support support using the provided async_context
+ *  \ingroup pico_lwip
+ *
+ *  If the initialization succeeds, \ref lwip_nosys_deinit() can be called to shutdown lwIP support
+ *
+ * \param context the async_context instance that provides the abstraction for handling asynchronous work.
+ * \return true if the initialization succeeded
+*/
+bool lwip_nosys_init(async_context_t *context);
+
+/*! \brief De-initialize lwIP (NO_SYS=1 mode) support
+ *  \ingroup pico_lwip
+ *
+ * Note that since lwIP may only be initialized once, and doesn't itself provide a shutdown mechanism, lwIP
+ * itself may still consume resources
+ *
+ * It is however safe to call \ref lwip_nosys_init again later.
+ *
+ * \param context the async_context the lwip_nosys support was added to via \ref lwip_nosys_init
+*/
+void lwip_nosys_deinit(async_context_t *context);
+
+#ifdef __cplusplus
+}
+#endif
+#endif

src/rp2_common/pico_lwip/lwip_freertos.c

@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2022 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+// todo graham #ifdef for LWIP inclusion?
+
+#include "pico/async_context.h"
+#include "pico/time.h"
+#include "lwip/tcpip.h"
+#include "lwip/timeouts.h"
+
+#include "FreeRTOS.h"
+#include "semphr.h"
+
+#if NO_SYS
+#error lwip_freertos_async_context_bindings requires NO_SYS=0
+#endif
+
+static async_context_t * volatile lwip_context;
+// lwIP tcpip_task cannot be shutdown, so we block it when we are de-initialized.
+static SemaphoreHandle_t tcpip_task_blocker;
+
+static void tcpip_init_done(void *param) {
+    xSemaphoreGive((SemaphoreHandle_t)param);
+}
+
+bool lwip_freertos_init(async_context_t *context) {
+    assert(!lwip_context);
+    lwip_context = context;
+    static bool done_lwip_init;
+    if (!done_lwip_init) {
+        done_lwip_init = true;
+        SemaphoreHandle_t init_sem = xSemaphoreCreateBinary();
+        tcpip_task_blocker = xSemaphoreCreateBinary();
+        tcpip_init(tcpip_init_done, init_sem);
+        xSemaphoreTake(init_sem, portMAX_DELAY);
+        vSemaphoreDelete(init_sem);
+    } else {
+        xSemaphoreGive(tcpip_task_blocker);
+    }
+    return true;
+}
+
+static uint32_t clear_lwip_context(__unused void *param) {
+    lwip_context = NULL;
+    return 0;
+}
+
+void lwip_freertos_deinit(__unused async_context_t *context) {
+    // clear the lwip context under lock as lwIP may still be running in tcpip_task
+    async_context_execute_sync(context, clear_lwip_context, NULL);
+}
+
+void pico_lwip_custom_lock_tcpip_core(void) {
+    while (!lwip_context) {
+        xSemaphoreTake(tcpip_task_blocker, portMAX_DELAY);
+    }
+    async_context_acquire_lock_blocking(lwip_context);
+}
+
+void pico_lwip_custom_unlock_tcpip_core(void) {
+    async_context_release_lock(lwip_context);
+}

src/rp2_common/pico_lwip/lwip_nosys.c

@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) 2022 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include "pico/async_context.h"
+
+#include <lwip/init.h>
+#include "lwip/timeouts.h"
+
+static void update_next_timeout(async_context_t *context, async_when_pending_worker_t *worker);
+static void lwip_timeout_reached(async_context_t *context, async_at_time_worker_t *worker);
+
+static async_when_pending_worker_t always_pending_update_timeout_worker = {
+        .do_work = update_next_timeout
+};
+
+static async_at_time_worker_t lwip_timeout_worker = {
+        .do_work = lwip_timeout_reached,
+};
+
+static void lwip_timeout_reached(__unused async_context_t *context, __unused async_at_time_worker_t *worker) {
+    assert(worker == &lwip_timeout_worker);
+    sys_check_timeouts();
+}
+
+static void update_next_timeout(async_context_t *context, async_when_pending_worker_t *worker) {
+    assert(worker == &always_pending_update_timeout_worker);
+    // we want to run on every execution of the helper to re-reflect any changes
+    // to the underlying lwIP timers which may have happened in the interim
+    // (note that worker will be called on every outermost exit of the async_context
+    // lock, and lwIP timers should not be modified whilst not holding the lock.
+    worker->work_pending = true;
+    uint32_t sleep_ms = sys_timeouts_sleeptime();
+    if (sleep_ms == SYS_TIMEOUTS_SLEEPTIME_INFINITE) {
+        lwip_timeout_worker.next_time = at_the_end_of_time;
+    } else {
+        lwip_timeout_worker.next_time = make_timeout_time_ms(sleep_ms);
+    }
+    async_context_add_at_time_worker(context, &lwip_timeout_worker);
+}
+
+bool lwip_nosys_init(async_context_t *context) {
+    static bool done_lwip_init;
+    if (!done_lwip_init) {
+        lwip_init();
+        done_lwip_init = true;
+    }
+    // we want the worker to be called on every async helper run (starting with the next)
+    always_pending_update_timeout_worker.work_pending = true;
+    async_context_add_when_pending_worker(context, &always_pending_update_timeout_worker);
+    return true;
+}
+
+void lwip_nosys_deinit(async_context_t *context) {
+    async_context_remove_at_time_worker(context, &lwip_timeout_worker);
+    async_context_remove_when_pending_worker(context, &always_pending_update_timeout_worker);
+}
+
+#if NO_SYS
+/* lwip has provision for using a mutex, when applicable */
+sys_prot_t sys_arch_protect(void) {
+    return 0;
+}
+
+void sys_arch_unprotect(__unused sys_prot_t pval) {
+}
+
+/* lwip needs a millisecond time source, and the TinyUSB board support code has one available */
+uint32_t sys_now(void) {
+    return to_ms_since_boot(get_absolute_time());
+}
+#endif

src/rp2_common/pico_lwip/nosys.c

@@ -1,26 +0,0 @@
-/*
- * Copyright (c) 2022 Raspberry Pi (Trading) Ltd.
- *
- * SPDX-License-Identifier: BSD-3-Clause
- */
-
-#include "lwip/init.h"
-#include "pico/time.h"
-
-#if NO_SYS
-/* lwip has provision for using a mutex, when applicable */
-sys_prot_t sys_arch_protect(void) {
-    return 0;
-}
-
-void sys_arch_unprotect(sys_prot_t pval) {
-    (void) pval;
-}
-
-/* lwip needs a millisecond time source, and the TinyUSB board support code has one available */
-uint32_t sys_now(void) {
-    return to_ms_since_boot(get_absolute_time());
-}
-
-#endif
-

src/rp2_common/pico_platform/include/pico/platform.h

@@ -314,6 +314,12 @@ void __attribute__((noreturn)) panic_unsupported(void);
  */
 void __attribute__((noreturn)) panic(const char *fmt, ...);
 
+#ifdef NDEBUG
+#define panic_compact(...) panic(__VA_ARGS__)
+#else
+#define panic_compact(...) panic("")
+#endif
+
 // PICO_CONFIG: PICO_NO_FPGA_CHECK, Remove the FPGA platform check for small code size reduction, type=bool, default=0, advanced=true, group=pico_runtime
 #ifndef PICO_NO_FPGA_CHECK
 #define PICO_NO_FPGA_CHECK 0