Add support for Arduino Nano RP2040 Connect (#425)

* Add support for Arduino Nano RP2040 Connect

* Add support for at25sf128a flash

Derived from W25Q080 code, QE bit is set via a single command

src/boards/include/boards/arduino_nano_rp2040_connect.h

@@ -0,0 +1,88 @@
+/*
+ * Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+// -----------------------------------------------------
+// NOTE: THIS HEADER IS ALSO INCLUDED BY ASSEMBLER SO
+//       SHOULD ONLY CONSIST OF PREPROCESSOR DIRECTIVES
+// -----------------------------------------------------
+
+#ifndef _BOARDS_ARDUINO_NANO_RP2040_CONNECT_H
+#define _BOARDS_ARDUINO_NANO_RP2040_CONNECT_H
+
+// For board detection
+#define ARDUINO_NANO_RP2040_CONNECT
+
+//------------- UART -------------//
+#ifndef PICO_DEFAULT_UART
+#define PICO_DEFAULT_UART 0
+#endif
+
+#ifndef PICO_DEFAULT_UART_TX_PIN
+#define PICO_DEFAULT_UART_TX_PIN 0
+#endif
+
+#ifndef PICO_DEFAULT_UART_RX_PIN
+#define PICO_DEFAULT_UART_RX_PIN 1
+#endif
+
+//------------- LED -------------//
+#ifndef PICO_DEFAULT_LED_PIN
+#define PICO_DEFAULT_LED_PIN 6
+#endif
+// no PICO_DEFAULT_WS2812_PIN
+
+//------------- I2C -------------//
+#ifndef PICO_DEFAULT_I2C
+#define PICO_DEFAULT_I2C 0
+#endif
+
+#ifndef PICO_DEFAULT_I2C_SDA_PIN
+#define PICO_DEFAULT_I2C_SDA_PIN 12
+#endif
+
+#ifndef PICO_DEFAULT_I2C_SCL_PIN
+#define PICO_DEFAULT_I2C_SCL_PIN 13
+#endif
+
+//------------- SPI -------------//
+#ifndef PICO_DEFAULT_SPI
+#define PICO_DEFAULT_SPI 0
+#endif
+
+#ifndef PICO_DEFAULT_SPI_TX_PIN
+#define PICO_DEFAULT_SPI_TX_PIN 7
+#endif
+
+#ifndef PICO_DEFAULT_SPI_RX_PIN
+#define PICO_DEFAULT_SPI_RX_PIN 4
+#endif
+
+#ifndef PICO_DEFAULT_SPI_SCK_PIN
+#define PICO_DEFAULT_SPI_SCK_PIN 6
+#endif
+
+//------------- FLASH -------------//
+
+#define PICO_BOOT_STAGE2_CHOOSE_AT25SF128A 1
+
+#ifndef PICO_FLASH_SPI_CLKDIV
+#define PICO_FLASH_SPI_CLKDIV 2
+#endif
+
+#ifndef PICO_FLASH_SIZE_BYTES
+#define PICO_FLASH_SIZE_BYTES (16 * 1024 * 1024)
+#endif
+
+// All boards have B1 RP2040
+#ifndef PICO_FLOAT_SUPPORT_ROM_V1
+#define PICO_FLOAT_SUPPORT_ROM_V1 0
+#endif
+
+#ifndef PICO_DOUBLE_SUPPORT_ROM_V1
+#define PICO_DOUBLE_SUPPORT_ROM_V1 0
+#endif
+
+#endif

src/rp2_common/boot_stage2/boot2_at25sf128a.S

@@ -0,0 +1,285 @@
+// ----------------------------------------------------------------------------
+// Second stage boot code
+// Copyright (c) 2019-2021 Raspberry Pi (Trading) Ltd.
+// SPDX-License-Identifier: BSD-3-Clause
+//
+// Device:      Adesto AT25SF128A
+//              Based on W25Q080 code: main difference is the QE bit is being set
+//              via command 0x31
+//
+// Description: Configures AT25SF128A to run in Quad I/O continuous read XIP mode
+//
+// Details:     * Check status register 2 to determine if QSPI mode is enabled,
+//                and perform an SR2 programming cycle if necessary.
+//              * Use SSI to perform a dummy 0xEB read command, with the mode
+//                continuation bits set, so that the flash will not require
+//                0xEB instruction prefix on subsequent reads.
+//              * Configure SSI to write address, mode bits, but no instruction.
+//                SSI + flash are now jointly in a state where continuous reads
+//                can take place.
+//              * Jump to exit pointer passed in via lr. Bootrom passes null,
+//                in which case this code uses a default 256 byte flash offset
+//
+// Building:    * This code must be position-independent, and use stack only
+//              * The code will be padded to a size of 256 bytes, including a
+//                4-byte checksum. Therefore code size cannot exceed 252 bytes.
+// ----------------------------------------------------------------------------
+
+#include "pico/asm_helper.S"
+#include "hardware/regs/addressmap.h"
+#include "hardware/regs/ssi.h"
+#include "hardware/regs/pads_qspi.h"
+
+// ----------------------------------------------------------------------------
+// Config section
+// ----------------------------------------------------------------------------
+// It should be possible to support most flash devices by modifying this section
+
+// The serial flash interface will run at clk_sys/PICO_FLASH_SPI_CLKDIV.
+// This must be a positive, even integer.
+// The bootrom is very conservative with SPI frequency, but here we should be
+// as aggressive as possible.
+
+#ifndef PICO_FLASH_SPI_CLKDIV
+#define PICO_FLASH_SPI_CLKDIV 4
+#endif
+#if PICO_FLASH_SPI_CLKDIV & 1
+#error PICO_FLASH_SPI_CLKDIV must be even
+#endif
+
+// Define interface width: single/dual/quad IO
+#define FRAME_FORMAT SSI_CTRLR0_SPI_FRF_VALUE_QUAD
+
+// For W25Q080 this is the "Read data fast quad IO" instruction:
+#define CMD_READ 0xeb
+
+// "Mode bits" are 8 special bits sent immediately after
+// the address bits in a "Read Data Fast Quad I/O" command sequence. 
+// On W25Q080, the four LSBs are don't care, and if MSBs == 0xa, the
+// next read does not require the 0xeb instruction prefix.
+#define MODE_CONTINUOUS_READ 0x20
+
+// The number of address + mode bits, divided by 4 (always 4, not function of
+// interface width).
+#define ADDR_L 8
+
+// How many clocks of Hi-Z following the mode bits. For W25Q080, 4 dummy cycles
+// are required.
+#define WAIT_CYCLES 4
+
+// If defined, we will read status reg, compare to SREG_DATA, and overwrite
+// with our value if the SR doesn't match.
+// We do a two-byte write to SR1 (01h cmd) rather than a one-byte write to
+// SR2 (31h cmd) as the latter command isn't supported by WX25Q080.
+// This isn't great because it will remove block protections.
+// A better solution is to use a volatile SR write if your device supports it.
+#define PROGRAM_STATUS_REG
+
+#define CMD_WRITE_ENABLE 0x06
+#define CMD_READ_STATUS 0x05
+#define CMD_READ_STATUS2 0x35
+#define CMD_WRITE_STATUS 0x01
+#define CMD_WRITE_STATUS2 0x31
+#define SREG_DATA 0x02  // Enable quad-SPI mode
+
+// ----------------------------------------------------------------------------
+// Start of 2nd Stage Boot Code
+// ----------------------------------------------------------------------------
+
+.syntax unified
+.cpu cortex-m0plus
+.thumb
+
+.section .text
+
+// The exit point is passed in lr. If entered from bootrom, this will be the
+// flash address immediately following this second stage (0x10000100).
+// Otherwise it will be a return address -- second stage being called as a
+// function by user code, after copying out of XIP region. r3 holds SSI base,
+// r0...2 used as temporaries. Other GPRs not used.
+.global _stage2_boot
+.type _stage2_boot,%function
+.thumb_func
+_stage2_boot:
+    push {lr}
+
+    // Set pad configuration:
+    // - SCLK 8mA drive, no slew limiting
+    // - SDx disable input Schmitt to reduce delay
+
+    ldr r3, =PADS_QSPI_BASE
+    movs r0, #(2 << PADS_QSPI_GPIO_QSPI_SCLK_DRIVE_LSB | PADS_QSPI_GPIO_QSPI_SCLK_SLEWFAST_BITS)
+    str r0, [r3, #PADS_QSPI_GPIO_QSPI_SCLK_OFFSET]
+    ldr r0, [r3, #PADS_QSPI_GPIO_QSPI_SD0_OFFSET]
+    movs r1, #PADS_QSPI_GPIO_QSPI_SD0_SCHMITT_BITS
+    bics r0, r1
+    str r0, [r3, #PADS_QSPI_GPIO_QSPI_SD0_OFFSET]
+    str r0, [r3, #PADS_QSPI_GPIO_QSPI_SD1_OFFSET]
+    str r0, [r3, #PADS_QSPI_GPIO_QSPI_SD2_OFFSET]
+    str r0, [r3, #PADS_QSPI_GPIO_QSPI_SD3_OFFSET]
+
+    ldr r3, =XIP_SSI_BASE
+
+    // Disable SSI to allow further config
+    movs r1, #0
+    str r1, [r3, #SSI_SSIENR_OFFSET]
+
+    // Set baud rate
+    movs r1, #PICO_FLASH_SPI_CLKDIV
+    str r1, [r3, #SSI_BAUDR_OFFSET]
+
+    // Set 1-cycle sample delay. If PICO_FLASH_SPI_CLKDIV == 2 then this means,
+    // if the flash launches data on SCLK posedge, we capture it at the time that
+    // the next SCLK posedge is launched. This is shortly before that posedge
+    // arrives at the flash, so data hold time should be ok. For
+    // PICO_FLASH_SPI_CLKDIV > 2 this pretty much has no effect.
+
+    movs r1, #1
+    movs r2, #SSI_RX_SAMPLE_DLY_OFFSET  // == 0xf0 so need 8 bits of offset significance
+    str r1, [r3, r2]
+
+
+// On QSPI parts we usually need a 01h SR-write command to enable QSPI mode
+// (i.e. turn WPn and HOLDn into IO2/IO3)
+#ifdef PROGRAM_STATUS_REG
+program_sregs:
+#define CTRL0_SPI_TXRX \
+    (7 << SSI_CTRLR0_DFS_32_LSB) | /* 8 bits per data frame */ \
+    (SSI_CTRLR0_TMOD_VALUE_TX_AND_RX << SSI_CTRLR0_TMOD_LSB)
+
+    ldr r1, =(CTRL0_SPI_TXRX)
+    str r1, [r3, #SSI_CTRLR0_OFFSET]
+
+     // Enable SSI and select slave 0
+    movs r1, #1
+    str r1, [r3, #SSI_SSIENR_OFFSET]
+
+    // Check whether SR needs updating
+    movs r0, #CMD_READ_STATUS2
+    bl read_flash_sreg
+    movs r2, #SREG_DATA
+    cmp r0, r2
+    beq skip_sreg_programming
+
+    // Send write enable command
+    movs r1, #CMD_WRITE_ENABLE
+    str r1, [r3, #SSI_DR0_OFFSET]
+
+    // Poll for completion and discard RX
+    bl wait_ssi_ready
+    ldr r1, [r3, #SSI_DR0_OFFSET]
+
+    // Send status write command followed by data bytes
+    movs r1, #CMD_WRITE_STATUS2
+    str r1, [r3, #SSI_DR0_OFFSET]
+    str r2, [r3, #SSI_DR0_OFFSET]
+
+    bl wait_ssi_ready
+    ldr r1, [r3, #SSI_DR0_OFFSET]
+    ldr r1, [r3, #SSI_DR0_OFFSET]
+    ldr r1, [r3, #SSI_DR0_OFFSET]
+
+    // Poll status register for write completion
+1:
+    movs r0, #CMD_READ_STATUS
+    bl read_flash_sreg
+    movs r1, #1
+    tst r0, r1
+    bne 1b
+
+skip_sreg_programming:
+
+    // Disable SSI again so that it can be reconfigured
+    movs r1, #0
+    str r1, [r3, #SSI_SSIENR_OFFSET]
+#endif
+
+// Currently the flash expects an 8 bit serial command prefix on every
+// transfer, which is a waste of cycles. Perform a dummy Fast Read Quad I/O
+// command, with mode bits set such that the flash will not expect a serial
+// command prefix on *subsequent* transfers. We don't care about the results
+// of the read, the important part is the mode bits.
+
+dummy_read:
+#define CTRLR0_ENTER_XIP \
+    (FRAME_FORMAT                          /* Quad I/O mode */                \
+        << SSI_CTRLR0_SPI_FRF_LSB) |                                          \
+    (31 << SSI_CTRLR0_DFS_32_LSB)  |       /* 32 data bits */                 \
+    (SSI_CTRLR0_TMOD_VALUE_EEPROM_READ     /* Send INST/ADDR, Receive Data */ \
+        << SSI_CTRLR0_TMOD_LSB)
+
+    ldr r1, =(CTRLR0_ENTER_XIP)
+    str r1, [r3, #SSI_CTRLR0_OFFSET]
+
+    movs r1, #0x0                    // NDF=0 (single 32b read)
+    str r1, [r3, #SSI_CTRLR1_OFFSET]
+
+#define SPI_CTRLR0_ENTER_XIP \
+    (ADDR_L << SSI_SPI_CTRLR0_ADDR_L_LSB) |     /* Address + mode bits */ \
+    (WAIT_CYCLES << SSI_SPI_CTRLR0_WAIT_CYCLES_LSB) | /* Hi-Z dummy clocks following address + mode */ \
+    (SSI_SPI_CTRLR0_INST_L_VALUE_8B \
+        << SSI_SPI_CTRLR0_INST_L_LSB) |        /* 8-bit instruction */ \
+    (SSI_SPI_CTRLR0_TRANS_TYPE_VALUE_1C2A      /* Send Command in serial mode then address in Quad I/O mode */ \
+        << SSI_SPI_CTRLR0_TRANS_TYPE_LSB)
+
+    ldr r1, =(SPI_CTRLR0_ENTER_XIP)
+    ldr r0, =(XIP_SSI_BASE + SSI_SPI_CTRLR0_OFFSET)  // SPI_CTRL0 Register
+    str r1, [r0]
+
+    movs r1, #1                      // Re-enable SSI
+    str r1, [r3, #SSI_SSIENR_OFFSET]
+
+    movs r1, #CMD_READ
+    str r1, [r3, #SSI_DR0_OFFSET]   // Push SPI command into TX FIFO
+    movs r1, #MODE_CONTINUOUS_READ   // 32-bit: 24 address bits (we don't care, so 0) and M[7:4]=1010
+    str r1, [r3, #SSI_DR0_OFFSET]   // Push Address into TX FIFO - this will trigger the transaction
+
+    // Poll for completion
+    bl wait_ssi_ready
+
+// The flash is in a state where we can blast addresses in parallel, and get
+// parallel data back. Now configure the SSI to translate XIP bus accesses
+// into QSPI transfers of this form.
+
+    movs r1, #0
+    str r1, [r3, #SSI_SSIENR_OFFSET]   // Disable SSI (and clear FIFO) to allow further config
+
+// Note that the INST_L field is used to select what XIP data gets pushed into
+// the TX FIFO:
+//      INST_L_0_BITS   {ADDR[23:0],XIP_CMD[7:0]}       Load "mode bits" into XIP_CMD
+//      Anything else   {XIP_CMD[7:0],ADDR[23:0]}       Load SPI command into XIP_CMD
+configure_ssi:
+#define SPI_CTRLR0_XIP \
+    (MODE_CONTINUOUS_READ                      /* Mode bits to keep flash in continuous read mode */ \
+        << SSI_SPI_CTRLR0_XIP_CMD_LSB) | \
+    (ADDR_L << SSI_SPI_CTRLR0_ADDR_L_LSB) |    /* Total number of address + mode bits */ \
+    (WAIT_CYCLES << SSI_SPI_CTRLR0_WAIT_CYCLES_LSB) |    /* Hi-Z dummy clocks following address + mode */ \
+    (SSI_SPI_CTRLR0_INST_L_VALUE_NONE          /* Do not send a command, instead send XIP_CMD as mode bits after address */ \
+        << SSI_SPI_CTRLR0_INST_L_LSB) | \
+    (SSI_SPI_CTRLR0_TRANS_TYPE_VALUE_2C2A      /* Send Address in Quad I/O mode (and Command but that is zero bits long) */ \
+        << SSI_SPI_CTRLR0_TRANS_TYPE_LSB)
+
+    ldr r1, =(SPI_CTRLR0_XIP)
+    ldr r0, =(XIP_SSI_BASE + SSI_SPI_CTRLR0_OFFSET)
+    str r1, [r0]
+
+    movs r1, #1
+    str r1, [r3, #SSI_SSIENR_OFFSET]   // Re-enable SSI
+
+// Bus accesses to the XIP window will now be transparently serviced by the
+// external flash on cache miss. We are ready to run code from flash.
+
+// Pull in standard exit routine
+#include "boot2_helpers/exit_from_boot2.S"
+
+// Common functions
+#include "boot2_helpers/wait_ssi_ready.S"
+#ifdef PROGRAM_STATUS_REG
+#include "boot2_helpers/read_flash_sreg.S"
+#endif
+
+.global literals
+literals:
+.ltorg
+
+.end

src/rp2_common/boot_stage2/include/boot_stage2/config.h

@@ -44,6 +44,16 @@
     #endif
     #define _BOOT_STAGE2_SELECTED
 #endif
+// PICO_CONFIG: PICO_BOOT_STAGE2_CHOOSE_AT25SF128A, Select boot2_at25sf128a as the boot stage 2 when no boot stage 2 selection is made by the CMake build, type=bool, default=0, group=boot_stage2
+#ifndef PICO_BOOT_STAGE2_CHOOSE_AT25SF128A
+    #define PICO_BOOT_STAGE2_CHOOSE_AT25SF128A 0
+#elif PICO_BOOT_STAGE2_CHOOSE_AT25SF128A
+    #ifdef _BOOT_STAGE2_SELECTED
+        #error multiple boot stage 2 options chosen
+    #endif
+    #define _BOOT_STAGE2_SELECTED
+#endif
+
 // PICO_CONFIG: PICO_BOOT_STAGE2_CHOOSE_GENERIC_03H, Select boot2_generic_03h as the boot stage 2 when no boot stage 2 selection is made by the CMake build, type=bool, default=1, group=boot_stage2
 #if defined(PICO_BOOT_STAGE2_CHOOSE_GENERIC_03H) && PICO_BOOT_STAGE2_CHOOSE_GENERIC_03H
     #ifdef _BOOT_STAGE2_SELECTED
@@ -65,6 +75,8 @@
         #define _BOOT_STAGE2 boot2_w25q080
     #elif PICO_BOOT_STAGE2_CHOOSE_W25X10CL
         #define _BOOT_STAGE2 boot2_w25x10cl
+    #elif PICO_BOOT_STAGE2_CHOOSE_AT25SF128A
+        #define _BOOT_STAGE2 boot2_at25sf128a
     #elif !defined(PICO_BOOT_STAGE2_CHOOSE_GENERIC_03H) || PICO_BOOT_STAGE2_CHOOSE_GENERIC_03H
         #undef PICO_BOOT_STAGE2_CHOOSE_GENERIC_03H
         #define PICO_BOOT_STAGE2_CHOOSE_GENERIC_03H 1