linux-kernel - [PATCH 5.5 103/189] spi: spidev: Fix CS polarity if GPIO descriptors are used

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Date:   Tue, 10 Mar 2020 13:39:00 +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, Simon Han <z.han@...bus.com>,
        Lukas Wunner <lukas@...ner.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        Mark Brown <broonie@...nel.org>
Subject: [PATCH 5.5 103/189] spi: spidev: Fix CS polarity if GPIO descriptors are used

From: Lukas Wunner <lukas@...ner.de>

commit 138c9c32f090894614899eca15e0bb7279f59865 upstream.

Commit f3186dd87669 ("spi: Optionally use GPIO descriptors for CS GPIOs")
amended of_spi_parse_dt() to always set SPI_CS_HIGH for SPI slaves whose
Chip Select is defined by a "cs-gpios" devicetree property.

This change broke userspace applications which issue an SPI_IOC_WR_MODE
ioctl() to an spidev:  Chip Select polarity will be incorrect unless the
application is changed to set SPI_CS_HIGH.  And once changed, it will be
incompatible with kernels not containing the commit.

Fix by setting SPI_CS_HIGH in spidev_ioctl() (under the same conditions
as in of_spi_parse_dt()).

Fixes: f3186dd87669 ("spi: Optionally use GPIO descriptors for CS GPIOs")
Reported-by: Simon Han <z.han@...bus.com>
Signed-off-by: Lukas Wunner <lukas@...ner.de>
Reviewed-by: Linus Walleij <linus.walleij@...aro.org>
Link: https://lore.kernel.org/r/fca3ba7cdc930cd36854666ceac4fbcf01b89028.1582027457.git.lukas@wunner.de
Signed-off-by: Mark Brown <broonie@...nel.org>
Cc: stable@...r.kernel.org # v5.1+
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/spi/spidev.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/drivers/spi/spidev.c
+++ b/drivers/spi/spidev.c
@@ -396,6 +396,7 @@ spidev_ioctl(struct file *filp, unsigned
 		else
 			retval = get_user(tmp, (u32 __user *)arg);
 		if (retval == 0) {
+			struct spi_controller *ctlr = spi->controller;
 			u32	save = spi->mode;
 
 			if (tmp & ~SPI_MODE_MASK) {
@@ -403,6 +404,10 @@ spidev_ioctl(struct file *filp, unsigned
 				break;
 			}
 
+			if (ctlr->use_gpio_descriptors && ctlr->cs_gpiods &&
+			    ctlr->cs_gpiods[spi->chip_select])
+				tmp |= SPI_CS_HIGH;
+
 			tmp |= spi->mode & ~SPI_MODE_MASK;
 			spi->mode = (u16)tmp;
 			retval = spi_setup(spi);