linux-kernel - [PATCH v2] spi: Fix incorrect cs

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Message-Id: <20211210170534.177139-1-marcan@marcan.st>
Date:   Sat, 11 Dec 2021 02:05:34 +0900
From:   Hector Martin <marcan@...can.st>
To:     Mark Brown <broonie@...nel.org>
Cc:     linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Joey Gouly <joey.gouly@....com>,
        Hector Martin <marcan@...can.st>
Subject: [PATCH v2] spi: Fix incorrect cs_setup delay handling

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>
---
 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