altos: Disable STM SPI transceiver when idle

Should save a bit of power.

Signed-off-by: Keith Packard <keithp@keithp.com>

diff --git a/src/stm/ao_arch_funcs.h b/src/stm/ao_arch_funcs.h
index 29e3f42f069a368e2dac1ed353523cd6a774679b..e0ecb0a56ee4e7b6f91a8b89ca44b5800ec0af62 100644 (file)
--- a/src/stm/ao_arch_funcs.h
+++ b/src/stm/ao_arch_funcs.h
@@ -22,8 +22,11 @@
  */
 extern uint8_t ao_spi_mutex[STM_NUM_SPI];
 
-static inline void ao_spi_get(uint8_t spi_index) { ao_mutex_get(&ao_spi_mutex[spi_index]); }
-static inline void ao_spi_put(uint8_t spi_index) { ao_mutex_put(&ao_spi_mutex[spi_index]); }
+void
+ao_spi_get(uint8_t spi_index);
+
+void
+ao_spi_put(uint8_t spi_index);
 
 void
 ao_spi_send(void *block, uint16_t len, uint8_t spi_index);

diff --git a/src/stm/ao_spi_stm.c b/src/stm/ao_spi_stm.c
index da04302b25d5cfb4fea5f1979542ea952eab88f9..92747d87c94bca49f9403704ce19050d4ff28586 100644 (file)
--- a/src/stm/ao_spi_stm.c
+++ b/src/stm/ao_spi_stm.c
@@ -47,6 +47,7 @@ ao_spi_send(void *block, uint16_t len, uint8_t spi_index)
        uint8_t mosi_dma_index = ao_spi_stm_info[spi_index].mosi_dma_index;
        uint8_t miso_dma_index = ao_spi_stm_info[spi_index].miso_dma_index;
 
+       /* Set up the transmit DMA to deliver data */
        ao_dma_set_transfer(mosi_dma_index,
                            &stm_spi->dr,
                            block,
@@ -59,8 +60,14 @@ ao_spi_send(void *block, uint16_t len, uint8_t spi_index)
                            (0 << STM_DMA_CCR_PINC) |
                            (0 << STM_DMA_CCR_CIRC) |
                            (STM_DMA_CCR_DIR_MEM_TO_PER << STM_DMA_CCR_DIR));
-       /* Clear any stale data */
+
+       /* Clear RXNE */
        (void) stm_spi->dr;
+
+       /* Set up the receive DMA -- when this is done, we know the SPI unit
+        * is idle. Without this, we'd have to poll waiting for the BSY bit to
+        * be cleared
+        */
        ao_dma_set_transfer(miso_dma_index,
                            &stm_spi->dr,
                            &spi_dev_null,
@@ -93,19 +100,10 @@ void
 ao_spi_recv(void *block, uint16_t len, uint8_t spi_index)
 {
        struct stm_spi *stm_spi = ao_spi_stm_info[spi_index].stm_spi;
-#if 0
-       uint8_t *d = block;
-
-       while (len--) {
-               stm_spi->dr = 0xff;
-               while (!(stm_spi->sr & (1 << STM_SPI_SR_RXNE)));
-               *d++ = stm_spi->dr;
-       }
-       while (stm_spi->sr & (1 << STM_SPI_SR_BSY));
-#else
        uint8_t mosi_dma_index = ao_spi_stm_info[spi_index].mosi_dma_index;
        uint8_t miso_dma_index = ao_spi_stm_info[spi_index].miso_dma_index;
 
+       /* Set up transmit DMA to make the SPI hardware actually run */
        ao_dma_set_transfer(mosi_dma_index,
                            &stm_spi->dr,
                            &spi_dev_null,
@@ -118,8 +116,11 @@ ao_spi_recv(void *block, uint16_t len, uint8_t spi_index)
                            (0 << STM_DMA_CCR_PINC) |
                            (0 << STM_DMA_CCR_CIRC) |
                            (STM_DMA_CCR_DIR_MEM_TO_PER << STM_DMA_CCR_DIR));
-       /* Clear any stale data */
+
+       /* Clear RXNE */
        (void) stm_spi->dr;
+
+       /* Set up the receive DMA to capture data */
        ao_dma_set_transfer(miso_dma_index,
                            &stm_spi->dr,
                            block,
@@ -132,6 +133,7 @@ ao_spi_recv(void *block, uint16_t len, uint8_t spi_index)
                            (0 << STM_DMA_CCR_PINC) |
                            (0 << STM_DMA_CCR_CIRC) |
                            (STM_DMA_CCR_DIR_PER_TO_MEM << STM_DMA_CCR_DIR));
+
        stm_spi->cr2 = ((0 << STM_SPI_CR2_TXEIE) |
                        (0 << STM_SPI_CR2_RXNEIE) |
                        (0 << STM_SPI_CR2_ERRIE) |
@@ -140,36 +142,55 @@ ao_spi_recv(void *block, uint16_t len, uint8_t spi_index)
                        (1 << STM_SPI_CR2_RXDMAEN));
        ao_dma_start(miso_dma_index);
        ao_dma_start(mosi_dma_index);
+
+       /* Wait until the SPI unit is done */
        ao_arch_critical(
                while (!ao_dma_done[miso_dma_index])
                        ao_sleep(&ao_dma_done[miso_dma_index]);
                );
+
        ao_dma_done_transfer(mosi_dma_index);
        ao_dma_done_transfer(miso_dma_index);
-#endif
 }
 
-static void
-ao_spi_channel_init(uint8_t spi_index)
+void
+ao_spi_get(uint8_t spi_index)
 {
        struct stm_spi  *stm_spi = ao_spi_stm_info[spi_index].stm_spi;
 
-       stm_spi->cr1 = 0;
-       (void) stm_spi->sr;
-       stm_spi->cr1 = ((0 << STM_SPI_CR1_BIDIMODE) |
+       ao_mutex_get(&ao_spi_mutex[spi_index]);
+       stm_spi->cr1 = ((0 << STM_SPI_CR1_BIDIMODE) |                   /* Three wire mode */
                        (0 << STM_SPI_CR1_BIDIOE) |
-                       (0 << STM_SPI_CR1_CRCEN) |
+                       (0 << STM_SPI_CR1_CRCEN) |                      /* CRC disabled */
                        (0 << STM_SPI_CR1_CRCNEXT) |
                        (0 << STM_SPI_CR1_DFF) |
                        (0 << STM_SPI_CR1_RXONLY) |
-                       (1 << STM_SPI_CR1_SSM) |
-                       (1 << STM_SPI_CR1_SSI) |
-                       (0 << STM_SPI_CR1_LSBFIRST) |
-                       (1 << STM_SPI_CR1_SPE) |
-                       (STM_SPI_CR1_BR_PCLK_4 << STM_SPI_CR1_BR) |
+                       (1 << STM_SPI_CR1_SSM) |                        /* Software SS handling */
+                       (1 << STM_SPI_CR1_SSI) |                        /*  ... */
+                       (0 << STM_SPI_CR1_LSBFIRST) |                   /* Little endian */
+                       (1 << STM_SPI_CR1_SPE) |                        /* Enable SPI unit */
+                       (STM_SPI_CR1_BR_PCLK_4 << STM_SPI_CR1_BR) |     /* baud rate to pclk/4 */
                        (1 << STM_SPI_CR1_MSTR) |
-                       (0 << STM_SPI_CR1_CPOL) |
+                       (0 << STM_SPI_CR1_CPOL) |                       /* Format 0 */
                        (0 << STM_SPI_CR1_CPHA));
+}
+
+void
+ao_spi_put(uint8_t spi_index)
+{
+       struct stm_spi  *stm_spi = ao_spi_stm_info[spi_index].stm_spi;
+
+       stm_spi->cr1 = 0;
+       ao_mutex_put(&ao_spi_mutex[spi_index]);
+}
+
+static void
+ao_spi_channel_init(uint8_t spi_index)
+{
+       struct stm_spi  *stm_spi = ao_spi_stm_info[spi_index].stm_spi;
+
+       stm_spi->cr1 = 0;
+       (void) stm_spi->sr;
        stm_spi->cr2 = ((0 << STM_SPI_CR2_TXEIE) |
                        (0 << STM_SPI_CR2_RXNEIE) |
                        (0 << STM_SPI_CR2_ERRIE) |