[PATCH 5.4 096/168] spi: spidev: Fix CS polarity if GPIO descriptors are used

Greg Kroah-Hartman
2020-03-10T12:52:16Z

From: Lukas Wunner <lukas@wunner.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@kunbus.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/fca3ba7cdc930cd36854666ceac4fbcf01b89028.1582027457.git.lukas@wunner.de
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org # v5.1+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/drivers/spi/spidev.c
+++ b/drivers/spi/spidev.c
@@ -394,6 +394,7 @@ 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) {
@@ -401,6 +402,10 @@ 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);