[PATCH 2/6] irqchip/al-fic: switch to shared parent interrupt

[Eliav Farber <farbere@amazon.com>]

Until now the driver requested its parent interrupt using the chained
IRQ API (irq_set_chained_handler_and_data()), which only works when each
parent interrupt is wired to a single FIC instance.

On some platforms several FIC instances share the same parent GIC SPI.
To support that, request the parent interrupt as a shared interrupt
(IRQF_SHARED) instead of installing a chained handler. The handler now
has the standard irqreturn_t prototype and reports whether it handled any
child interrupt, so the shared-IRQ core can dispatch to the correct
instance.

generic_handle_domain_irq() is retained for dispatch; its return value is
used to determine whether a pending child was actually handled so the
handler can return IRQ_HANDLED/IRQ_NONE correctly.

Signed-off-by: Eliav Farber <farbere@amazon.com>
---
 drivers/irqchip/irq-al-fic.c | 30 ++++++++++++++++++------------
 1 file changed, 18 insertions(+), 12 deletions(-)

diff --git a/drivers/irqchip/irq-al-fic.c b/drivers/irqchip/irq-al-fic.c
index efa7f2b62d00..9cf3eedac97f 100644
--- a/drivers/irqchip/irq-al-fic.c
+++ b/drivers/irqchip/irq-al-fic.c
@@ -4,9 +4,9 @@
  */
 
 #include <linux/bitfield.h>
+#include <linux/interrupt.h>
 #include <linux/irq.h>
 #include <linux/irqchip.h>
-#include <linux/irqchip/chained_irq.h>
 #include <linux/irqdomain.h>
 #include <linux/module.h>
 #include <linux/of.h>
@@ -95,24 +95,24 @@ static int al_fic_irq_set_type(struct irq_data *data, unsigned int flow_type)
 	return 0;
 }
 
-static void al_fic_irq_handler(struct irq_desc *desc)
+static irqreturn_t al_fic_irq_handler(int irq, void *data)
 {
-	struct al_fic *fic = irq_desc_get_handler_data(desc);
+	struct al_fic *fic = data;
 	struct irq_domain *domain = fic->domain;
-	struct irq_chip *irqchip = irq_desc_get_chip(desc);
 	struct irq_chip_generic *gc = irq_get_domain_generic_chip(domain, 0);
+	irqreturn_t ret = IRQ_NONE;
 	unsigned long pending;
 	u32 hwirq;
 
-	chained_irq_enter(irqchip, desc);
-
 	pending = readl_relaxed(fic->base + AL_FIC_CAUSE);
 	pending &= ~gc->mask_cache;
 
-	for_each_set_bit(hwirq, &pending, NR_FIC_IRQS)
-		generic_handle_domain_irq(domain, hwirq);
+	for_each_set_bit(hwirq, &pending, NR_FIC_IRQS) {
+		if (!generic_handle_domain_irq(domain, hwirq))
+			ret = IRQ_HANDLED;
+	}
 
-	chained_irq_exit(irqchip, desc);
+	return ret;
 }
 
 static int al_fic_irq_retrigger(struct irq_data *data)
@@ -162,11 +162,17 @@ static int al_fic_register(struct device_node *node,
 	gc->chip_types->chip.flags = IRQCHIP_SKIP_SET_WAKE;
 	gc->private = fic;
 
-	irq_set_chained_handler_and_data(fic->parent_irq,
-					 al_fic_irq_handler,
-					 fic);
+	ret = request_irq(fic->parent_irq, al_fic_irq_handler,
+			  IRQF_NO_THREAD | IRQF_SHARED, fic->name, fic);
+	if (ret) {
+		pr_err("fail to request irq (%d)\n", ret);
+		goto err_free_generic_chip;
+	}
+
 	return 0;
 
+err_free_generic_chip:
+	irq_free_generic_chip(gc);
 err_domain_remove:
 	irq_domain_remove(fic->domain);
 
-- 
2.47.3