spi: take the SPI IO-mutex in the spi_set_cs_timing method

this patch takes the io_mutex to prevent an unprotected HW
register modification in the set_cs_timing callback.

Fixes: 4cea6b8cc34e ("spi: add power control when set_cs_timing")
Signed-off-by: Leilk Liu <leilk.liu@mediatek.com>
Link: https://lore.kernel.org/r/20210508060214.1485-1-leilk.liu@mediatek.com
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index f9885c0..a565e7d 100644 (file)
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -3457,9 +3457,12 @@ int spi_set_cs_timing(struct spi_device *spi, struct spi_delay *setup,
 
        if (spi->controller->set_cs_timing &&
            !(spi->cs_gpiod || gpio_is_valid(spi->cs_gpio))) {
+               mutex_lock(&spi->controller->io_mutex);
+
                if (spi->controller->auto_runtime_pm) {
                        status = pm_runtime_get_sync(parent);
                        if (status < 0) {
+                               mutex_unlock(&spi->controller->io_mutex);
                                pm_runtime_put_noidle(parent);
                                dev_err(&spi->controller->dev, "Failed to power device: %d\n",
                                        status);
@@ -3470,11 +3473,13 @@ int spi_set_cs_timing(struct spi_device *spi, struct spi_delay *setup,
                                                                hold, inactive);
                        pm_runtime_mark_last_busy(parent);
                        pm_runtime_put_autosuspend(parent);
-                       return status;
                } else {
-                       return spi->controller->set_cs_timing(spi, setup, hold,
+                       status = spi->controller->set_cs_timing(spi, setup, hold,
                                                              inactive);
                }
+
+               mutex_unlock(&spi->controller->io_mutex);
+               return status;
        }
 
        if ((setup && setup->unit == SPI_DELAY_UNIT_SCK) ||