[PATCH] gpio: pca953x: fix pca953x_irq_bus_sync_unlock regmap lock

[Mark Tomlinson]

Locking is disabled in the regmap config as this driver uses its own
lock. This means that all calls to regmap functions (read or write) must
hold the i2c_lock. The function pca953x_irq_bus_sync_unlock() did not do
this, and it was therefore possible that multiple threads could cause an
incorrect register to be read/written.

A previous patch partly fixed this, but only protected the write to the
interrupt mask register, and not the read from the direction register.

Signed-off-by: Mark Tomlinson <mark.tomlinson@xxxxxxxxxxxxxxxxxxx>
---
 drivers/gpio/gpio-pca953x.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/gpio/gpio-pca953x.c b/drivers/gpio/gpio-pca953x.c
index 2ee35e855e4d..9689e3f3c517 100644
--- a/drivers/gpio/gpio-pca953x.c
+++ b/drivers/gpio/gpio-pca953x.c
@@ -605,20 +605,27 @@ static int pca953x_read_regs(struct pca953x_chip *chip, int reg, unsigned long *
 	return 0;
 }
 
-static int pca953x_gpio_direction_input(struct gpio_chip *gc, unsigned off)
+static int _pca953x_gpio_direction_input(struct gpio_chip *gc, unsigned off)
 {
 	struct pca953x_chip *chip = gpiochip_get_data(gc);
 	u8 dirreg = chip->recalc_addr(chip, chip->regs->direction, off);
 	u8 bit = pca953x_get_bit_mask(chip, off);
 
-	guard(mutex)(&chip->i2c_lock);
-
 	if (PCA_CHIP_TYPE(chip->driver_data) == TCA6418_TYPE)
 		return regmap_update_bits(chip->regmap, dirreg, bit, 0);
 
 	return regmap_update_bits(chip->regmap, dirreg, bit, bit);
 }
 
+static int pca953x_gpio_direction_input(struct gpio_chip *gc, unsigned off)
+{
+	struct pca953x_chip *chip = gpiochip_get_data(gc);
+
+	guard(mutex)(&chip->i2c_lock);
+
+	return _pca953x_gpio_direction_input(gc, off);
+}
+
 static int pca953x_gpio_direction_output(struct gpio_chip *gc,
 		unsigned off, int val)
 {
@@ -856,9 +863,10 @@ static void pca953x_irq_bus_sync_unlock(struct irq_data *d)
 	DECLARE_BITMAP(reg_direction, MAX_LINE);
 	int level;
 
+	guard(mutex)(&chip->i2c_lock);
+
 	if (chip->driver_data & PCA_PCAL) {
 		DECLARE_BITMAP(latched_inputs, MAX_LINE);
-		guard(mutex)(&chip->i2c_lock);
 
 		/* Enable latch on edge-triggered interrupt-enabled inputs */
 		bitmap_or(latched_inputs, chip->irq_trig_fall, chip->irq_trig_raise, gc->ngpio);
@@ -880,7 +888,7 @@ static void pca953x_irq_bus_sync_unlock(struct irq_data *d)
 
 	/* Look for any newly setup interrupt */
 	for_each_andnot_bit(level, irq_mask, reg_direction, gc->ngpio)
-		pca953x_gpio_direction_input(&chip->gpio_chip, level);
+		_pca953x_gpio_direction_input(&chip->gpio_chip, level);
 
 	mutex_unlock(&chip->irq_lock);
 }
-- 
2.54.0