irqchip/al-fic: Add support for irq retrigger

Introduce interrupts retrigger support for Amazon's Annapurna Labs Fabric
Interrupt Controller.
Signed-off-by: Talel Shenhar <talel@amazon.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/1568018358-18985-1-git-send-email-talel@amazon.com

drivers/irqchip/irq-al-fic.c

@@ -15,6 +15,7 @@
 
 /* FIC Registers */
 #define AL_FIC_CAUSE		0x00
+#define AL_FIC_SET_CAUSE	0x08
 #define AL_FIC_MASK		0x10
 #define AL_FIC_CONTROL		0x28
 
@@ -126,6 +127,16 @@ static void al_fic_irq_handler(struct irq_desc *desc)
 	chained_irq_exit(irqchip, desc);
 }
 
+static int al_fic_irq_retrigger(struct irq_data *data)
+{
+	struct irq_chip_generic *gc = irq_data_get_irq_chip_data(data);
+	struct al_fic *fic = gc->private;
+
+	writel_relaxed(BIT(data->hwirq), fic->base + AL_FIC_SET_CAUSE);
+
+	return 1;
+}
+
 static int al_fic_register(struct device_node *node,
 			   struct al_fic *fic)
 {
@@ -159,6 +170,7 @@ static int al_fic_register(struct device_node *node,
 	gc->chip_types->chip.irq_unmask = irq_gc_mask_clr_bit;
 	gc->chip_types->chip.irq_ack = irq_gc_ack_clr_bit;
 	gc->chip_types->chip.irq_set_type = al_fic_irq_set_type;
+	gc->chip_types->chip.irq_retrigger = al_fic_irq_retrigger;
 	gc->chip_types->chip.flags = IRQCHIP_SKIP_SET_WAKE;
 	gc->private = fic;