gpio: set parent irq on chained handlers

If the IRQ from the parent is nested the IRQ may need to be
resent under certain conditions. Currently the chained IRQ
handler in gpiolib does not handle connecting nested IRQs
but it is conceptually correct to indicate the actual parent
IRQ.

Reported-by: Grygorii Strashko <grygorii.strashko@ti.com>
Reported-by: Lothar Waßmann <LW@karo-electronics.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpiolib.c

@@ -398,17 +398,30 @@ void gpiochip_set_chained_irqchip(struct gpio_chip *gpiochip,
 				  int parent_irq,
 				  irq_flow_handler_t parent_handler)
 {
+	unsigned int offset;
+
 	if (gpiochip->can_sleep) {
 		chip_err(gpiochip, "you cannot have chained interrupts on a chip that may sleep\n");
 		return;
 	}
+	if (!gpiochip->irqdomain) {
+		chip_err(gpiochip, "called %s before setting up irqchip\n",
+			 __func__);
+		return;
+	}
 
 	irq_set_chained_handler(parent_irq, parent_handler);
+
 	/*
 	 * The parent irqchip is already using the chip_data for this
 	 * irqchip, so our callbacks simply use the handler_data.
 	 */
 	irq_set_handler_data(parent_irq, gpiochip);
+
+	/* Set the parent IRQ for all affected IRQs */
+	for (offset = 0; offset < gpiochip->ngpio; offset++)
+		irq_set_parent(irq_find_mapping(gpiochip->irqdomain, offset),
+			       parent_irq);
 }
 EXPORT_SYMBOL_GPL(gpiochip_set_chained_irqchip);