[PATCH] irqchip: omap-intc: improve IRQ handler

[Felipe Balbi]

as it turns out the current IRQ number will
*always* be available from SIR register which
renders the reads of PENDING registers as plain
unnecessary overhead.

In order to catch any situation where SIR reads
as zero, we're adding a WARN() to turn it into
a very verbose error and users actually report
it.

With this patch average running time of
omap_intc_handle_irq() reduced from about 28.5us
to 19.8us as measured by the kernel function
profiler.

Tested with BeagleBoneBlack Rev A5C.

Signed-off-by: Felipe Balbi <balbi at ti.com>
---

Before applying, it would be very nice to get reports
from other folks on different platforms, specially OMAP2/3
ones which I don't have (easy) access.

 drivers/irqchip/irq-omap-intc.c | 35 +++++------------------------------
 1 file changed, 5 insertions(+), 30 deletions(-)

diff --git a/drivers/irqchip/irq-omap-intc.c b/drivers/irqchip/irq-omap-intc.c
index 28718d3..a2da6d5 100644
--- a/drivers/irqchip/irq-omap-intc.c
+++ b/drivers/irqchip/irq-omap-intc.c
@@ -315,37 +315,12 @@ static int __init omap_init_irq(u32 base, struct device_node *node)
 static asmlinkage void __exception_irq_entry
 omap_intc_handle_irq(struct pt_regs *regs)
 {
-	u32 irqnr = 0;
-	int handled_irq = 0;
-	int i;
-
-	do {
-		for (i = 0; i < omap_nr_pending; i++) {
-			irqnr = intc_readl(INTC_PENDING_IRQ0 + (0x20 * i));
-			if (irqnr)
-				goto out;
-		}
-
-out:
-		if (!irqnr)
-			break;
-
-		irqnr = intc_readl(INTC_SIR);
-		irqnr &= ACTIVEIRQ_MASK;
+	u32 irqnr;
 
-		if (irqnr) {
-			handle_domain_irq(domain, irqnr, regs);
-			handled_irq = 1;
-		}
-	} while (irqnr);
-
-	/*
-	 * If an irq is masked or deasserted while active, we will
-	 * keep ending up here with no irq handled. So remove it from
-	 * the INTC with an ack.
-	 */
-	if (!handled_irq)
-		omap_ack_irq(NULL);
+	irqnr = intc_readl(INTC_SIR);
+	irqnr &= ACTIVEIRQ_MASK;
+	WARN(!irqnr, "Spuriour IRQ ?\n");
+	handle_domain_irq(domain, irqnr, regs);
 }
 
 void __init omap2_init_irq(void)
-- 
2.2.0