FAILED: patch "[PATCH] gpio: pca953x: fix IRQ storm on system wake up" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-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-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 3e38f946062b4845961ab86b726651b4457b2af8
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025051942-diagnoses-sequence-8a2a@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 3e38f946062b4845961ab86b726651b4457b2af8 Mon Sep 17 00:00:00 2001
From: Emanuele Ghidoli <[email protected]>
Date: Mon, 12 May 2025 11:54:41 +0200
Subject: [PATCH] gpio: pca953x: fix IRQ storm on system wake up

If an input changes state during wake-up and is used as an interrupt source, the IRQ handler reads the volatile input register to clear the interrupt mask and deassert the IRQ line. However, the IRQ handler is triggered before access to the register is granted, causing the read operation to fail.

As a result, the IRQ handler enters a loop, repeatedly printing the "failed reading register" message, until pca953x_resume() is eventually called, which restores the driver context and enables access to registers.

Fix by disabling the IRQ line before entering suspend mode, and re-enabling it after the driver context is restored in pca953x_resume().

An IRQ can be disabled with disable_irq() and still wake the system as long as the IRQ has wake enabled, so the wake-up functionality is preserved.

index 442435ded020..13cc120cf11f 100644
@@ -1204,6 +1204,8 @@ static int pca953x_restore_context(struct pca953x_chip *chip)
 
 	guard(mutex)(&chip->i2c_lock);
 
+	if (chip->client->irq > 0)
+		enable_irq(chip->client->irq);
 	regcache_cache_only(chip->regmap, false);
 	regcache_mark_dirty(chip->regmap);
 	ret = pca953x_regcache_sync(chip);

@@ -1216,6 +1218,10 @@ static int pca953x_restore_context(struct pca953x_chip *chip)
 static void pca953x_save_context(struct pca953x_chip *chip)
 {
 	guard(mutex)(&chip->i2c_lock);
+
+	/* Disable IRQ to prevent early triggering while regmap "cache only" is on */
+	if (chip->client->irq > 0)
+		disable_irq(chip->client->irq);
 	regcache_cache_only(chip->regmap, true);
 }
 

From: Emanuele Ghidoli <[email protected]>

[ Upstream commit 3e38f946062b4845961ab86b726651b4457b2af8 ]

If an input changes state during wake-up and is used as an interrupt source, the IRQ handler reads the volatile input register to clear the interrupt mask and deassert the IRQ line. However, the IRQ handler is triggered before access to the register is granted, causing the read operation to fail.

As a result, the IRQ handler enters a loop, repeatedly printing the "failed reading register" message, until pca953x_resume() is eventually called, which restores the driver context and enables access to registers.

Fix by disabling the IRQ line before entering suspend mode, and re-enabling it after the driver context is restored in pca953x_resume().

An IRQ can be disabled with disable_irq() and still wake the system as long as the IRQ has wake enabled, so the wake-up functionality is preserved.

---
 drivers/gpio/gpio-pca953x.c | 5 +++++
 1 file changed, 5 insertions(+)

index 45f3836c4f0fa..a8f6ef4006fef 100644
@@ -1145,6 +1145,9 @@ static int pca953x_suspend(struct device *dev)
 	struct pca953x_chip *chip = dev_get_drvdata(dev);
 
 	mutex_lock(&chip->i2c_lock);
+	/* Disable IRQ to prevent early triggering while regmap "cache only" is on */
+	if (chip->client->irq > 0)
+		disable_irq(chip->client->irq);
 	regcache_cache_only(chip->regmap, true);
 	mutex_unlock(&chip->i2c_lock);
 

@@ -1170,6 +1173,8 @@ static int pca953x_resume(struct device *dev)
 	}
 
 	mutex_lock(&chip->i2c_lock);
+	if (chip->client->irq > 0)
+		enable_irq(chip->client->irq);
 	regcache_cache_only(chip->regmap, false);
 	regcache_mark_dirty(chip->regmap);
 	ret = pca953x_regcache_sync(dev);

2.50.1