linux-kernel - [PATCH 5.15 240/846] spi: Fix incorrect cs

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Date:   Mon, 24 Jan 2022 19:35:57 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hector Martin <marcan@...can.st>,
        Mark Brown <broonie@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 240/846] spi: Fix incorrect cs_setup delay handling

From: Hector Martin <marcan@...can.st>

[ Upstream commit 95c07247399536f83b89dc60cfe7b279d17e69f6 ]

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@...can.st>
Link: https://lore.kernel.org/r/20211210170534.177139-1-marcan@marcan.st
Signed-off-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 97b5a811bd7f7..a42b9e8521ce0 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -868,12 +868,9 @@ 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)
@@ -915,7 +912,9 @@ 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);
 	}
 }
-- 
2.34.1