[03/18] spi: stm32h7: remove unused mode fault MODF event handling

Commit Message

Alain Volmat Aug. 5, 2020, 7:01 a.m. UTC

From: Antonio Borneo <[e-mail]>

Accordingly to STM32H7 document RM0433, "mode fault" MODF is
a special mode to handle a spi bus with multiple masters, in
which each master has to "detect" if another master enables
its CS to take control of the bus. Once this is detected,
all other masters has to temporarily switch to "slave" mode.

Such multi-master mode is not supported in Linux and this
driver properly disables the mode by setting the bits
SPI_CR1_SSI and SPI_CFG2_SSM, thus forcing a master only
operating mode.

In this condition, we will never receive an interrupt due to
MODF event and we do not need to handle it.

Remove all the unused code around handling MODF events.

Signed-off-by: Antonio Borneo <[e-mail]>
Signed-off-by: Alain Volmat <[e-mail]>
---
 drivers/spi/spi-stm32.c | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

Comments

Mark Brown Aug. 5, 2020, 10:51 a.m. UTC | #1

On Wed, Aug 05, 2020 at 09:01:58AM +0200, Alain Volmat wrote:
> From: Antonio Borneo <[e-mail]>

> Accordingly to STM32H7 document RM0433, "mode fault" MODF is
> a special mode to handle a spi bus with multiple masters, in
> which each master has to "detect" if another master enables
> its CS to take control of the bus. Once this is detected,
> all other masters has to temporarily switch to "slave" mode.

> Such multi-master mode is not supported in Linux and this
> driver properly disables the mode by setting the bits
> SPI_CR1_SSI and SPI_CFG2_SSM, thus forcing a master only
> operating mode.

> In this condition, we will never receive an interrupt due to
> MODF event and we do not need to handle it.

> Remove all the unused code around handling MODF events.

What does having this cost us?  Hopefully it's not doing much but if
something goes wrong with the hardware and this does get flagged up for
some reason it'd be good to know about it.  It doesn't seem to be having
a big impact on the code or anything.

Patch

diff --git a/drivers/spi/spi-stm32.c b/drivers/spi/spi-stm32.c
index eaa416c551c9..df22dea784d9 100644
--- a/drivers/spi/spi-stm32.c
+++ b/drivers/spi/spi-stm32.c
@@ -129,7 +129,6 @@ 
 #define STM32H7_SPI_IER_EOTIE		BIT(3)
 #define STM32H7_SPI_IER_TXTFIE		BIT(4)
 #define STM32H7_SPI_IER_OVRIE		BIT(6)
-#define STM32H7_SPI_IER_MODFIE		BIT(9)
 #define STM32H7_SPI_IER_ALL		GENMASK(10, 0)
 
 /* STM32H7_SPI_SR bit fields */
@@ -137,7 +136,6 @@ 
 #define STM32H7_SPI_SR_TXP		BIT(1)
 #define STM32H7_SPI_SR_EOT		BIT(3)
 #define STM32H7_SPI_SR_OVR		BIT(6)
-#define STM32H7_SPI_SR_MODF		BIT(9)
 #define STM32H7_SPI_SR_SUSP		BIT(11)
 #define STM32H7_SPI_SR_RXPLVL_SHIFT	13
 #define STM32H7_SPI_SR_RXPLVL		GENMASK(14, 13)
@@ -933,11 +931,6 @@  static irqreturn_t stm32h7_spi_irq_thread(int irq, void *dev_id)
 			end = true;
 	}
 
-	if (sr & STM32H7_SPI_SR_MODF) {
-		dev_warn(spi->dev, "Mode fault: transfer aborted\n");
-		end = true;
-	}
-
 	if (sr & STM32H7_SPI_SR_OVR) {
 		dev_warn(spi->dev, "Overrun: received value discarded\n");
 		if (!spi->cur_usedma && (spi->rx_buf && (spi->rx_len > 0)))
@@ -1201,7 +1194,7 @@  static int stm32h7_spi_transfer_one_irq(struct stm32_spi *spi)
 
 	/* Enable the interrupts relative to the end of transfer */
 	ier |= STM32H7_SPI_IER_EOTIE | STM32H7_SPI_IER_TXTFIE |
-	       STM32H7_SPI_IER_OVRIE | STM32H7_SPI_IER_MODFIE;
+	       STM32H7_SPI_IER_OVRIE;
 
 	spin_lock_irqsave(&spi->lock, flags);
 
@@ -1251,8 +1244,7 @@  static void stm32h7_spi_transfer_one_dma_start(struct stm32_spi *spi)
 	/* Enable the interrupts relative to the end of transfer */
 	stm32_spi_set_bits(spi, STM32H7_SPI_IER, STM32H7_SPI_IER_EOTIE |
 						 STM32H7_SPI_IER_TXTFIE |
-						 STM32H7_SPI_IER_OVRIE |
-						 STM32H7_SPI_IER_MODFIE);
+						 STM32H7_SPI_IER_OVRIE);
 
 	stm32_spi_enable(spi);