[PATCH v2] spi: Fix incorrect cs_setup delay handling

[PATCH v2] spi: Fix incorrect cs_setup delay handling

[Hector Martin]

Move the cs_setup delay to the end of spi_set_cs.

From include/linux/spi/spi.h:

 * @cs_setup: delay to be introduced by the controller after CS is
   asserted

The cs_setup delay needs to happen *after* CS is asserted, that is, at
the end of spi_set_cs, not at the beginning. Otherwise we're just
delaying before the SPI transaction starts at all, which isn't very
useful.

No drivers use this right now, but that is likely to change soon with an
upcoming Apple SPI HID transport driver.

Fixes: 25093bdeb6bc ("spi: implement SW control for CS times")
Signed-off-by: Hector Martin <marcan@marcan.st>
---
 drivers/spi/spi.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index b23e675953e1..cfb708d928b5 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -947,12 +947,9 @@ static void spi_set_cs(struct spi_device *spi, bool enable, bool force)
 	spi->controller->last_cs_enable = enable;
 	spi->controller->last_cs_mode_high = spi->mode & SPI_CS_HIGH;
 
-	if (spi->cs_gpiod || gpio_is_valid(spi->cs_gpio) ||
-	    !spi->controller->set_cs_timing) {
-		if (activate)
-			spi_delay_exec(&spi->cs_setup, NULL);
-		else
-			spi_delay_exec(&spi->cs_hold, NULL);
+	if ((spi->cs_gpiod || gpio_is_valid(spi->cs_gpio) ||
+	    !spi->controller->set_cs_timing) && !activate) {
+		spi_delay_exec(&spi->cs_hold, NULL);
 	}
 
 	if (spi->mode & SPI_CS_HIGH)
@@ -994,7 +991,9 @@ static void spi_set_cs(struct spi_device *spi, bool enable, bool force)
 
 	if (spi->cs_gpiod || gpio_is_valid(spi->cs_gpio) ||
 	    !spi->controller->set_cs_timing) {
-		if (!activate)
+		if (activate)
+			spi_delay_exec(&spi->cs_setup, NULL);
+		else
 			spi_delay_exec(&spi->cs_inactive, NULL);
 	}
 }
-- 
2.33.0

Re: [PATCH v2] spi: Fix incorrect cs_setup delay handling

[Mark Brown]

On Sat, 11 Dec 2021 02:05:34 +0900, Hector Martin wrote:
> Move the cs_setup delay to the end of spi_set_cs.
> 
> From include/linux/spi/spi.h:
> 
>  * @cs_setup: delay to be introduced by the controller after CS is
>    asserted
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-next

Thanks!

[1/1] spi: Fix incorrect cs_setup delay handling
      commit: 95c07247399536f83b89dc60cfe7b279d17e69f6

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark