spi: stm32: Add 'SPI_SIMPLEX_RX', 'SPI_3WIRE_RX' support for stm32f4

in l3gd20 driver startup, there is a setup failed error return from
stm32 spi driver

     "
     [    2.687630] st-gyro-spi spi0.0: supply vdd not found, using dummy
     regulator
     [    2.696869] st-gyro-spi spi0.0: supply vddio not found, using dummy
     regulator
     [    2.706707] spi_stm32 40015000.spi: SPI transfer setup failed
     [    2.713741] st-gyro-spi spi0.0: SPI transfer failed: -22
     [    2.721096] spi_master spi0: failed to transfer one message from queue
     [    2.729268] iio iio:device0: failed to read Who-Am-I register.
     [    2.737504] st-gyro-spi: probe of spi0.0 failed with error -22
     "

after debug into spi-stm32 driver, st-gyro-spi split two steps to read
l3gd20 id

first: send command to l3gd20 with read id command in tx_buf, rx_buf
is null.
second: read id with tx_buf is null, rx_buf not null.

so, for second step, stm32 driver recongise this process as 'SPI_SIMPLE_RX'
from stm32_spi_communication_type(), but there is no related process for this
type in stm32f4_spi_set_mode(), then we get error from
stm32_spi_transfer_one_setup().

we can use two method to fix this bug.
1, use stm32 spi's "In unidirectional receive-only mode (BIDIMODE=0 and
RXONLY=1)". but as our code running in sdram, the read latency is too large
to get so many receive overrun error in interrupts handler.

2, use stm32 spi's "In full-duplex (BIDIMODE=0 and RXONLY=0)", as tx_buf is
null, so add flag 'SPI_MASTER_MUST_TX' to spi master.

Change since V4:
1 remove dummy data sent out by stm32 spi driver
2 add flag 'SPI_MASTER_MUST_TX' to spi master

Signed-off-by: dillon min <dillon.minfei@gmail.com>
Link: https://lore.kernel.org/r/1590378348-8115-8-git-send-email-dillon.minfei@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/spi/spi-stm32.c b/drivers/spi/spi-stm32.c
index 44ac6eb..4c643df 100644 (file)
--- a/drivers/spi/spi-stm32.c
+++ b/drivers/spi/spi-stm32.c
@@ -811,7 +811,9 @@ static irqreturn_t stm32f4_spi_irq_event(int irq, void *dev_id)
                mask |= STM32F4_SPI_SR_TXE;
        }
 
-       if (!spi->cur_usedma && spi->cur_comm == SPI_FULL_DUPLEX) {
+       if (!spi->cur_usedma && (spi->cur_comm == SPI_FULL_DUPLEX ||
+                               spi->cur_comm == SPI_SIMPLEX_RX ||
+                               spi->cur_comm == SPI_3WIRE_RX)) {
                /* TXE flag is set and is handled when RXNE flag occurs */
                sr &= ~STM32F4_SPI_SR_TXE;
                mask |= STM32F4_SPI_SR_RXNE | STM32F4_SPI_SR_OVR;
@@ -850,7 +852,7 @@ static irqreturn_t stm32f4_spi_irq_event(int irq, void *dev_id)
                stm32f4_spi_read_rx(spi);
                if (spi->rx_len == 0)
                        end = true;
-               else /* Load data for discontinuous mode */
+               else if (spi->tx_buf)/* Load data for discontinuous mode */
                        stm32f4_spi_write_tx(spi);
        }
 
@@ -1151,7 +1153,9 @@ static int stm32f4_spi_transfer_one_irq(struct stm32_spi *spi)
        /* Enable the interrupts relative to the current communication mode */
        if (spi->cur_comm == SPI_SIMPLEX_TX || spi->cur_comm == SPI_3WIRE_TX) {
                cr2 |= STM32F4_SPI_CR2_TXEIE;
-       } else if (spi->cur_comm == SPI_FULL_DUPLEX) {
+       } else if (spi->cur_comm == SPI_FULL_DUPLEX ||
+                               spi->cur_comm == SPI_SIMPLEX_RX ||
+                               spi->cur_comm == SPI_3WIRE_RX) {
                /* In transmit-only mode, the OVR flag is set in the SR register
                 * since the received data are never read. Therefore set OVR
                 * interrupt only when rx buffer is available.
@@ -1462,10 +1466,16 @@ static int stm32f4_spi_set_mode(struct stm32_spi *spi, unsigned int comm_type)
                stm32_spi_set_bits(spi, STM32F4_SPI_CR1,
                                        STM32F4_SPI_CR1_BIDIMODE |
                                        STM32F4_SPI_CR1_BIDIOE);
-       } else if (comm_type == SPI_FULL_DUPLEX) {
+       } else if (comm_type == SPI_FULL_DUPLEX ||
+                               comm_type == SPI_SIMPLEX_RX) {
                stm32_spi_clr_bits(spi, STM32F4_SPI_CR1,
                                        STM32F4_SPI_CR1_BIDIMODE |
                                        STM32F4_SPI_CR1_BIDIOE);
+       } else if (comm_type == SPI_3WIRE_RX) {
+               stm32_spi_set_bits(spi, STM32F4_SPI_CR1,
+                                       STM32F4_SPI_CR1_BIDIMODE);
+               stm32_spi_clr_bits(spi, STM32F4_SPI_CR1,
+                                       STM32F4_SPI_CR1_BIDIOE);
        } else {
                return -EINVAL;
        }
@@ -1906,6 +1916,7 @@ static int stm32_spi_probe(struct platform_device *pdev)
        master->prepare_message = stm32_spi_prepare_msg;
        master->transfer_one = stm32_spi_transfer_one;
        master->unprepare_message = stm32_spi_unprepare_msg;
+       master->flags = SPI_MASTER_MUST_TX;
 
        spi->dma_tx = dma_request_chan(spi->dev, "tx");
        if (IS_ERR(spi->dma_tx)) {