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FAILED: patch "[PATCH] gpio: pca953x: fix pca953x_irq_bus_sync_unlock regmap lock" failed to apply to 6.18-stable tree

PATCH [email protected] 1 participant 1 message Aug 5

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The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 9dc325327babe7f159e84cbe9380a45342da0585
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026080529-subsystem-decorator-c2e3@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 9dc325327babe7f159e84cbe9380a45342da0585 Mon Sep 17 00:00:00 2001
From: Mark Tomlinson <[email protected]>
Date: Thu, 9 Jul 2026 16:51:16 +1200
Subject: [PATCH] gpio: pca953x: fix pca953x_irq_bus_sync_unlock regmap lock

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.

Fixes bfc6444b57dc ("gpio: pca953x: fix pca953x_irq_bus_sync_unlock race")
Cc [email protected]
Signed-off-by Mark Tomlinson <[email protected]>
Link https://patch.msgid.link/[email protected] open here
Signed-off-by Bartosz Golaszewski <[email protected]>
drivers/gpio/gpio-pca953x.c +14 -5
index f6b870b7b352..e03bf1b12091 100644
@@ -604,20 +604,28 @@ 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_unlocked(struct gpio_chip *gc,
+						 unsigned int 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 int off)
+{
+	struct pca953x_chip *chip = gpiochip_get_data(gc);
+
+	guard(mutex)(&chip->i2c_lock);
+
+	return pca953x_gpio_direction_input_unlocked(gc, off);
+}
+
 static int pca953x_gpio_direction_output(struct gpio_chip *gc,
 		unsigned off, int val)
 {

@@ -855,9 +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);

@@ -879,7 +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_unlocked(&chip->gpio_chip, level);
 
 	mutex_unlock(&chip->irq_lock);
 }