misc: microchip: pci1xxxx: Fix Kernel panic during IRQ handler registration

Resolve kernel panic while accessing IRQ handler associated with the
generated IRQ. This is done by acquiring the spinlock and storing the
current interrupt state before handling the interrupt request using
generic_handle_irq.

A previous fix patch was submitted where 'generic_handle_irq' was
replaced with 'handle_nested_irq'. However, this change also causes
the kernel panic where after determining which GPIO triggered the
interrupt and attempting to call handle_nested_irq with the mapped
IRQ number, leads to a failure in locating the registered handler.

Fixes: 194f9f9 ("misc: microchip: pci1xxxx: Resolve kernel panic during GPIO IRQ handling")
Cc: stable <stable@kernel.org>
Signed-off-by: Rengarajan S <rengarajan.s@microchip.com>
Link: https://lore.kernel.org/r/20250313170856.20868-2-rengarajan.s@microchip.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: RengarajanSS

drivers/misc/mchp_pci1xxxx/mchp_pci1xxxx_gpio.c

@@ -37,6 +37,7 @@
 struct pci1xxxx_gpio {
 	struct auxiliary_device *aux_dev;
 	void __iomem *reg_base;
+	raw_spinlock_t wa_lock;
 	struct gpio_chip gpio;
 	spinlock_t lock;
 	int irq_base;
@@ -257,6 +258,7 @@ static irqreturn_t pci1xxxx_gpio_irq_handler(int irq, void *dev_id)
 	struct pci1xxxx_gpio *priv = dev_id;
 	struct gpio_chip *gc =  &priv->gpio;
 	unsigned long int_status = 0;
+	unsigned long wa_flags;
 	unsigned long flags;
 	u8 pincount;
 	int bit;
@@ -280,7 +282,9 @@ static irqreturn_t pci1xxxx_gpio_irq_handler(int irq, void *dev_id)
 			writel(BIT(bit), priv->reg_base + INTR_STATUS_OFFSET(gpiobank));
 			spin_unlock_irqrestore(&priv->lock, flags);
 			irq = irq_find_mapping(gc->irq.domain, (bit + (gpiobank * 32)));
-			handle_nested_irq(irq);
+			raw_spin_lock_irqsave(&priv->wa_lock, wa_flags);
+			generic_handle_irq(irq);
+			raw_spin_unlock_irqrestore(&priv->wa_lock, wa_flags);
 		}
 	}
 	spin_lock_irqsave(&priv->lock, flags);