spi: spidev: Fix CS polarity if GPIO descriptors are used

Commit 9bc982f86df7 ("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: 9bc982f86df7 ("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+

diff --git a/drivers/spi/spidev.c b/drivers/spi/spidev.c
index 1e217e3e9486ebd9d1147a3e95700f43d5e7935f..2ab6e782f14c2527ae7c698d1975530594e33c70 100644 (file)
--- a/drivers/spi/spidev.c
+++ b/drivers/spi/spidev.c
@@ -396,6 +396,7 @@ spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
                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 int cmd, unsigned long arg)
                                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);