[PATCH v2] gpio: dwapb: Add robust error handling in interrupt handler

[Liang Hao]

The current interrupt handler silently continues if an interrupt
handling fails, which may lead to interrupt storms. Add proper
error handling to gracefully recover from failed interrupt
handling.

When generic_handle_irq() fails, the following recovery actions are
taken:
  - Write EOI to clear the pending interrupt
  - Mask the interrupt to prevent immediate re-triggering
  - Disable the interrupt to stop further interrupts on this line

Use scoped_guard(gpio_generic_lock_irqsave) to protect the read-
modify-write sequences on shared registers (GPIO_INTMASK and
GPIO_INTEN). This prevents race conditions with irq_chip callbacks
(dwapb_irq_mask, dwapb_irq_enable, etc.) that access the same
registers from different contexts.

These measures prevent the system from being overwhelmed by repeated
unhandled interrupts while logging a rate-limited warning for
debugging purposes.

Signed-off-by: Liang Hao <haohlliang@xxxxxxxxx>
---
v1 -> v2:
- Add spinlock protection for register access in error path
- Protect against race with irq_chip callbacks accessing shared registers
---
 drivers/gpio/gpio-dwapb.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/gpio/gpio-dwapb.c b/drivers/gpio/gpio-dwapb.c
index 7b92b233fafe..dc9676eb1429 100644
--- a/drivers/gpio/gpio-dwapb.c
+++ b/drivers/gpio/gpio-dwapb.c
@@ -209,8 +209,23 @@ static u32 dwapb_do_irq(struct dwapb_gpio *gpio)
 	for_each_set_bit(hwirq, &irq_status, DWAPB_MAX_GPIOS) {
 		int gpio_irq = irq_find_mapping(gen_gc->gc.irq.domain, hwirq);
 		u32 irq_type = irq_get_trigger_type(gpio_irq);
-
-		generic_handle_irq(gpio_irq);
+		int ret;
+		u32 val_intmask, val_inten;
+
+		ret = generic_handle_irq(gpio_irq);
+		if (ret) {
+			dev_warn_ratelimited(gpio->dev, "Failed to handle irq %d\n", gpio_irq);
+			/* Clear the interrupt */
+			scoped_guard(gpio_generic_lock_irqsave, gen_gc) {
+				/* Clear the interrupt */
+				dwapb_write(gpio, GPIO_PORTA_EOI, BIT(hwirq));
+				val_intmask = dwapb_read(gpio, GPIO_INTMASK);
+				dwapb_write(gpio, GPIO_INTMASK, val_intmask | BIT(hwirq));
+				val_inten = dwapb_read(gpio, GPIO_INTEN);
+				dwapb_write(gpio, GPIO_INTEN, val_inten & ~BIT(hwirq));
+			}
+			continue;
+		}
 
 		if ((irq_type & IRQ_TYPE_SENSE_MASK) == IRQ_TYPE_EDGE_BOTH)
 			dwapb_toggle_trigger(gpio, hwirq);
-- 
2.50.1 (Apple Git-155)