ARM: S5PV310: Optimize interrupt source searching code

It is reported by Junseok Jung that using clz instruction is
better instead of using for-loop to find the interrupt source.
This patch modifies interrupt source searching code using __ffs().
The __ffs() is implemented using clz instruction.

Suggested-by: Junseok Jung <jundols.jung@samsung.com>
Signed-off-by: Changhwan Youn <chaos.youn@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>

diff --git a/arch/arm/mach-s5pv310/irq-combiner.c b/arch/arm/mach-s5pv310/irq-combiner.c
index 0f7052164f23116500451253c58351f06e18fe57..c3f88c3faf6c79b943aabbe420d3aa2e976be761 100644 (file)
--- a/arch/arm/mach-s5pv310/irq-combiner.c
+++ b/arch/arm/mach-s5pv310/irq-combiner.c
@@ -66,11 +66,7 @@ static void combiner_handle_cascade_irq(unsigned int irq, struct irq_desc *desc)
        if (status == 0)
                goto out;
 
-       for (combiner_irq = 0; combiner_irq < 32; combiner_irq++) {
-               if (status & 0x1)
-                       break;
-               status >>= 1;
-       }
+       combiner_irq = __ffs(status);
 
        cascade_irq = combiner_irq + (chip_data->irq_offset & ~31);
        if (unlikely(cascade_irq >= NR_IRQS))