5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Ian Ray <ian.ray@xxxxxxxxxxxxxxxx>
[ Upstream commit bfc6444b57dc7186b6acc964705d7516cbaf3904 ]
Ensure that `i2c_lock' is held when setting interrupt latch and mask in
pca953x_irq_bus_sync_unlock() in order to avoid races.
The other (non-probe) call site pca953x_gpio_set_multiple() ensures the
lock is held before calling pca953x_write_regs().
The problem occurred when a request raced against irq_bus_sync_unlock()
approximately once per thousand reboots on an i.MX8MP based system.
* Normal case
0-0022: write register AI|3a {03,02,00,00,01} Input latch P0
0-0022: write register AI|49 {fc,fd,ff,ff,fe} Interrupt mask P0
0-0022: write register AI|08 {ff,00,00,00,00} Output P3
0-0022: write register AI|12 {fc,00,00,00,00} Config P3
* Race case
0-0022: write register AI|08 {ff,00,00,00,00} Output P3
0-0022: write register AI|08 {03,02,00,00,01} *** Wrong register ***
0-0022: write register AI|12 {fc,00,00,00,00} Config P3
0-0022: write register AI|49 {fc,fd,ff,ff,fe} Interrupt mask P0
Signed-off-by: Ian Ray <ian.ray@xxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240620042915.2173-1-ian.ray@xxxxxxxxxxxxxxxx
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/gpio/gpio-pca953x.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/gpio/gpio-pca953x.c b/drivers/gpio/gpio-pca953x.c
index c81d73d5e0159..d4c81373929af 100644
--- a/drivers/gpio/gpio-pca953x.c
+++ b/drivers/gpio/gpio-pca953x.c
@@ -696,6 +696,8 @@ static void pca953x_irq_bus_sync_unlock(struct irq_data *d)
pca953x_read_regs(chip, chip->regs->direction, reg_direction);
if (chip->driver_data & PCA_PCAL) {
+ guard(mutex)(&chip->i2c_lock);
+
/* Enable latch on interrupt-enabled inputs */
pca953x_write_regs(chip, PCAL953X_IN_LATCH, chip->irq_mask);
--
2.43.0
