added spi_get_baudrate() + some consistency changes (#395)

* added spi_get_baudrate()

src/rp2_common/hardware_spi/include/hardware/spi.h

@@ -132,13 +132,23 @@ void spi_deinit(spi_inst_t *spi);
  */
 uint spi_set_baudrate(spi_inst_t *spi, uint baudrate);
 
+/*! \brief Get SPI baudrate
+ *  \ingroup hardware_spi
+ *
+ * Get SPI baudrate which was set by \see spi_set_baudrate
+ *
+ * \param spi SPI instance specifier, either \ref spi0 or \ref spi1
+ * \return The actual baudrate set
+ */
+uint spi_get_baudrate(const spi_inst_t *spi);
+
 /*! \brief Convert SPI instance to hardware instance number
  *  \ingroup hardware_spi
  *
  * \param spi SPI instance
  * \return Number of SPI, 0 or 1.
  */
-static inline uint spi_get_index(spi_inst_t *spi) {
+static inline uint spi_get_index(const spi_inst_t *spi) {
     invalid_params_if(SPI, spi != spi0 && spi != spi1);
     return spi == spi1 ? 1 : 0;
 }
@@ -148,6 +158,11 @@ static inline spi_hw_t *spi_get_hw(spi_inst_t *spi) {
     return (spi_hw_t *)spi;
 }
 
+static inline const spi_hw_t *spi_get_const_hw(const spi_inst_t *spi) {
+    spi_get_index(spi);  // check it is a hw spi
+    return (const spi_hw_t *)spi;
+}
+
 /*! \brief Configure SPI
  *  \ingroup hardware_spi
  *
@@ -197,27 +212,30 @@ static inline void spi_set_slave(spi_inst_t *spi, bool slave) {
  *  \ingroup hardware_spi
  *
  * \param spi SPI instance specifier, either \ref spi0 or \ref spi1
- * \return 0 if no space is available to write. Non-zero if a write is possible
+ * \return false if no space is available to write. True if a write is possible
- *
- * \note Although the controllers each have a 8 deep TX FIFO, the current HW implementation can only return 0 or 1
- * rather than the space available.
  */
-static inline size_t spi_is_writable(spi_inst_t *spi) {
+static inline bool spi_is_writable(const spi_inst_t *spi) {
-    // PL022 doesn't expose levels directly, so return values are only 0 or 1
+    return (spi_get_const_hw(spi)->sr & SPI_SSPSR_TNF_BITS);
-    return (spi_get_hw(spi)->sr & SPI_SSPSR_TNF_BITS) >> SPI_SSPSR_TNF_LSB;
 }
 
 /*! \brief Check whether a read can be done on SPI device
  *  \ingroup hardware_spi
  *
  * \param spi SPI instance specifier, either \ref spi0 or \ref spi1
- * \return Non-zero if a read is possible i.e. data is present
+ * \return true if a read is possible i.e. data is present
- *
- * \note Although the controllers each have a 8 deep RX FIFO, the current HW implementation can only return 0 or 1
- * rather than the data available.
  */
-static inline size_t spi_is_readable(spi_inst_t *spi) {
+static inline bool spi_is_readable(const spi_inst_t *spi) {
-    return (spi_get_hw(spi)->sr & SPI_SSPSR_RNE_BITS) >> SPI_SSPSR_RNE_LSB;
+    return (spi_get_const_hw(spi)->sr & SPI_SSPSR_RNE_BITS);
+}
+
+/*! \brief Check whether SPI is busy
+ *  \ingroup hardware_spi
+ *
+ * \param spi SPI instance specifier, either \ref spi0 or \ref spi1
+ * \return true if SPI is busy
+ */
+static inline bool spi_is_busy(const spi_inst_t *spi) {
+    return (spi_get_const_hw(spi)->sr & SPI_SSPSR_BSY_BITS);
 }
 
 /*! \brief Write/Read to/from an SPI device

src/rp2_common/hardware_spi/spi.c

@@ -26,7 +26,6 @@ uint spi_init(spi_inst_t *spi, uint baudrate) {
     spi_set_format(spi, 8, SPI_CPOL_0, SPI_CPHA_0, SPI_MSB_FIRST);
     // Always enable DREQ signals -- harmless if DMA is not listening
     hw_set_bits(&spi_get_hw(spi)->dmacr, SPI_SSPDMACR_TXDMAE_BITS | SPI_SSPDMACR_RXDMAE_BITS);
-    spi_set_format(spi, 8, SPI_CPOL_0, SPI_CPHA_0, SPI_MSB_FIRST);
 
     // Finally enable the SPI
     hw_set_bits(&spi_get_hw(spi)->cr1, SPI_SSPCR1_SSE_BITS);
@@ -66,6 +65,12 @@ uint spi_set_baudrate(spi_inst_t *spi, uint baudrate) {
     return freq_in / (prescale * postdiv);
 }
 
+uint spi_get_baudrate(const spi_inst_t *spi) {
+    uint prescale = spi_get_const_hw(spi)->cpsr;
+    uint postdiv = ((spi_get_const_hw(spi)->cr0  & SPI_SSPCR0_SCR_BITS) >> SPI_SSPCR0_SCR_LSB) + 1;
+    return clock_get_hz(clk_peri) / (prescale * postdiv);
+}
+
 // Write len bytes from src to SPI. Simultaneously read len bytes from SPI to dst.
 // Note this function is guaranteed to exit in a known amount of time (bits sent * time per bit)
 int __not_in_flash_func(spi_write_read_blocking)(spi_inst_t *spi, const uint8_t *src, uint8_t *dst, size_t len) {