[PATCH] ARM: S5PV310: Optimize interrupt source searching code
Sergei Shtylyov
sshtylyov at mvista.com
Tue Sep 28 08:45:59 EDT 2010
Hello.
On 28-09-2010 5:31, Kukjin Kim wrote:
> From: Changhwan Youn<chaos.youn at samsung.com>
> 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 __fls().
> The __fls() is implemented using clz instruction.
> Suggested-by: Junseok Jung<jundols.jung at samsung.com>
> Signed-off-by: Changhwan Youn<chaos.youn at samsung.com>
> Signed-off-by: Kukjin Kim<kgene.kim at samsung.com>
> ---
> arch/arm/mach-s5pv310/irq-combiner.c | 6 +-----
> 1 files changed, 1 insertions(+), 5 deletions(-)
> diff --git a/arch/arm/mach-s5pv310/irq-combiner.c b/arch/arm/mach-s5pv310/irq-combiner.c
> index 0f70521..39e3647 100644
> --- 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 = __fls(status);
But the loop finds the *first* set bit, not the last...
WBR, Sergei
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