irqchip: omap-intc: Improve IRQ handler

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.

Tested-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Cc: Linux ARM Kernel Mailing List <linux-arm-kernel@lists.infradead.org>
Link: http://lkml.kernel.org/r/20150720204910.GH5394@saruman.tx.rr.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/drivers/irqchip/irq-omap-intc.c b/drivers/irqchip/irq-omap-intc.c
index 6cc0ad5..8587d0f 100644 (file)
--- a/drivers/irqchip/irq-omap-intc.c
+++ b/drivers/irqchip/irq-omap-intc.c
@@ -330,37 +330,12 @@ 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_ONCE(!irqnr, "Spurious IRQ ?\n");
+       handle_domain_irq(domain, irqnr, regs);
 }
 
 void __init omap3_init_irq(void)