[PATCH v4] gpio: dwapb: Mask interrupts at hardware initialization

[Liang Hao <haohlliang@gmail.com>]

GPIO interrupts may retain stale state across warm reboots when
peripherals remain powered. If a GPIO line is not explicitly
configured for interrupts, this can result in interrupt storms
due to missing handlers.

Fix this by ensuring all interrupts are masked and disabled at
hardware initialization time via the init_hw() callback. Pending
interrupts are also cleared to start from a known-safe state.

Interrupts will be unmasked only when explicitly configured by
userspace or kernel drivers.

Signed-off-by: Liang Hao <haohlliang@gmail.com>
---
v3 -> v4:
- Instead of handling errors in the interrupt handler, properly
  initialize hardware interrupt state at probe time via init_hw()
- This addresses the root cause identified by tglx rather than
  papering over the symptom

v2 -> v3:
- Remove duplicate comment

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 | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/gpio/gpio-dwapb.c b/drivers/gpio/gpio-dwapb.c
index 7b92b233fafe..3189a0269efc 100644
--- a/drivers/gpio/gpio-dwapb.c
+++ b/drivers/gpio/gpio-dwapb.c
@@ -199,6 +199,22 @@ static void dwapb_toggle_trigger(struct dwapb_gpio *gpio, unsigned int offs)
 	dwapb_write(gpio, GPIO_INT_POLARITY, pol);
 }
 
+static int dwapb_irq_init_hw(struct gpio_chip *gc)
+{
+	struct dwapb_gpio *gpio = to_dwapb_gpio(gc);
+
+	/*
+	 * GPIO interrupts may retain stale state across warm reboots when
+	 * peripherals stay powered. Force a known-safe state before the GPIO
+	 * irqchip and irq domain are set up.
+	 */
+	dwapb_write(gpio, GPIO_INTEN, 0);
+	dwapb_write(gpio, GPIO_INTMASK, 0xffffffff);
+	dwapb_write(gpio, GPIO_PORTA_EOI, 0xffffffff);
+
+	return 0;
+}
+
 static u32 dwapb_do_irq(struct dwapb_gpio *gpio)
 {
 	struct gpio_generic_chip *gen_gc = &gpio->ports[0].chip;
@@ -457,6 +473,7 @@ static void dwapb_configure_irqs(struct dwapb_gpio *gpio,
 	girq = &gc->irq;
 	girq->handler = handle_bad_irq;
 	girq->default_type = IRQ_TYPE_NONE;
+	girq->init_hw = dwapb_irq_init_hw;
 
 	port->pirq = pirq;
 
-- 
2.50.1 (Apple Git-155)