linux-kernel - [PATCH v2] gpio: pca953x: fix IRQ storm on system wake up

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Message-Id: <20250509141828.57851-1-francesco@dolcini.it>
Date: Fri,  9 May 2025 16:18:28 +0200
From: Francesco Dolcini <francesco@...cini.it>
To: Linus Walleij <linus.walleij@...aro.org>,
	Bartosz Golaszewski <brgl@...ev.pl>
Cc: Emanuele Ghidoli <emanuele.ghidoli@...adex.com>,
	linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Andy Shevchenko <andriy.shevchenko@...el.com>,
	Marek Vasut <marek.vasut@...il.com>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	stable@...r.kernel.org,
	Francesco Dolcini <francesco.dolcini@...adex.com>
Subject: [PATCH v2] gpio: pca953x: fix IRQ storm on system wake up

From: Emanuele Ghidoli <emanuele.ghidoli@...adex.com>

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.

Fixes: b76574300504 ("gpio: pca953x: Restore registers after suspend/resume cycle")
Cc: stable@...r.kernel.org
Signed-off-by: Emanuele Ghidoli <emanuele.ghidoli@...adex.com>
Signed-off-by: Francesco Dolcini <francesco.dolcini@...adex.com>
---
v1 -> v2
 - Instead of calling PM ops with disabled interrupts, just disable the
   irq while going in suspend and re-enable it after restoring the
   context in resume function.
---
 drivers/gpio/gpio-pca953x.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpio/gpio-pca953x.c b/drivers/gpio/gpio-pca953x.c
index ab2c0fd428fb..b852e4997629 100644
--- a/drivers/gpio/gpio-pca953x.c
+++ b/drivers/gpio/gpio-pca953x.c
@@ -1226,6 +1226,8 @@ 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);
@@ -1238,6 +1240,10 @@ 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);
 }
 
-- 
2.39.5