linux-kernel - [PATCH v2 1/1] pinctrl: ocelot: fix system hang on level based interrupts

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Message-Id: <20241012105743.12450-2-matsievskiysv@gmail.com>
Date: Sat, 12 Oct 2024 13:57:43 +0300
From: Sergey Matsievskiy <matsievskiysv@...il.com>
To: linus.walleij@...aro.org
Cc: alexandre.belloni@...tlin.com,
	quentin.schulz@...tlin.com,
	lars.povlsen@...rochip.com,
	horatiu.vultur@...rochip.com,
	andriy.shevchenko@...ux.intel.com,
	linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-mips@...r.kernel.org,
	UNGLinuxDriver@...rochip.com,
	Sergey Matsievskiy <matsievskiysv@...il.com>
Subject: [PATCH v2 1/1] pinctrl: ocelot: fix system hang on level based interrupts

The current implementation only calls chained_irq_enter() and
chained_irq_exit() if it detects pending interrupts.

```
for (i = 0; i < info->stride; i++) {
	uregmap_read(info->map, id_reg + 4 * i, &reg);
	if (!reg)
		continue;

	chained_irq_enter(parent_chip, desc);
```

However, in case of GPIO pin configured in level mode and the parent
controller configured in edge mode, GPIO interrupt might be lowered by the
hardware. In the result, if the interrupt is short enough, the parent
interrupt is still pending while the GPIO interrupt is cleared;
chained_irq_enter() never gets called and the system hangs trying to
service the parent interrupt.

Moving chained_irq_enter() and chained_irq_exit() outside the for loop
ensures that they are called even when GPIO interrupt is lowered by the
hardware.

The similar code with chained_irq_enter() / chained_irq_exit() functions
wrapping interrupt checking loop may be found in many other drivers:
```
grep -r -A 10 chained_irq_enter drivers/pinctrl
```

Signed-off-by: Sergey Matsievskiy <matsievskiysv@...il.com>
Reviewed-by: Alexandre Belloni <alexandre.belloni@...tlin.com>
---
 drivers/pinctrl/pinctrl-ocelot.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/pinctrl/pinctrl-ocelot.c b/drivers/pinctrl/pinctrl-ocelot.c
index be9b8c010167..d1ab8450ea93 100644
--- a/drivers/pinctrl/pinctrl-ocelot.c
+++ b/drivers/pinctrl/pinctrl-ocelot.c
@@ -1955,21 +1955,21 @@ static void ocelot_irq_handler(struct irq_desc *desc)
 	unsigned int reg = 0, irq, i;
 	unsigned long irqs;
 
+	chained_irq_enter(parent_chip, desc);
+
 	for (i = 0; i < info->stride; i++) {
 		regmap_read(info->map, id_reg + 4 * i, &reg);
 		if (!reg)
 			continue;
 
-		chained_irq_enter(parent_chip, desc);
-
 		irqs = reg;
 
 		for_each_set_bit(irq, &irqs,
 				 min(32U, info->desc->npins - 32 * i))
 			generic_handle_domain_irq(chip->irq.domain, irq + 32 * i);
-
-		chained_irq_exit(parent_chip, desc);
 	}
+
+	chained_irq_exit(parent_chip, desc);
 }
 
 static int ocelot_gpiochip_register(struct platform_device *pdev,
-- 
2.39.5