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Subject[PATCH v5 7/8] spi: stm32: Add 'SPI_SIMPLEX_RX', 'SPI_3WIRE_RX' support for stm32f4
Date
From: dillon min <dillon.minfei@gmail.com>

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>
---

Hi Mark,

This changes add 'SPI_MASTER_MUST_TX' for stm32 spi controller

thanks.


drivers/spi/spi-stm32.c | 19 +++++++++++++++----
1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/spi/spi-stm32.c b/drivers/spi/spi-stm32.c
index 44ac6eb3..4c643df 100644
--- 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)) {
--
2.7.4
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