* [PATCH] ARM: S5PV310: Optimize interrupt source searching code
@ 2010-09-28 1:31 Kukjin Kim
2010-09-28 12:45 ` Sergei Shtylyov
0 siblings, 1 reply; 5+ messages in thread
From: Kukjin Kim @ 2010-09-28 1:31 UTC (permalink / raw)
To: linux-arm-kernel
From: Changhwan Youn <chaos.youn@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@samsung.com>
Signed-off-by: Changhwan Youn <chaos.youn@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@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);
cascade_irq = combiner_irq + (chip_data->irq_offset & ~31);
if (unlikely(cascade_irq >= NR_IRQS))
--
1.6.2.5
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH] ARM: S5PV310: Optimize interrupt source searching code
2010-09-28 1:31 [PATCH] ARM: S5PV310: Optimize interrupt source searching code Kukjin Kim
@ 2010-09-28 12:45 ` Sergei Shtylyov
2010-09-28 13:01 ` Michał Nazarewicz
2010-09-28 13:10 ` Kukjin Kim
0 siblings, 2 replies; 5+ messages in thread
From: Sergei Shtylyov @ 2010-09-28 12:45 UTC (permalink / raw)
To: linux-arm-kernel
Hello.
On 28-09-2010 5:31, Kukjin Kim wrote:
> From: Changhwan Youn<chaos.youn@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@samsung.com>
> Signed-off-by: Changhwan Youn<chaos.youn@samsung.com>
> Signed-off-by: Kukjin Kim<kgene.kim@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
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH] ARM: S5PV310: Optimize interrupt source searching code
2010-09-28 12:45 ` Sergei Shtylyov
@ 2010-09-28 13:01 ` Michał Nazarewicz
2010-09-28 14:07 ` Kukjin Kim
2010-09-28 13:10 ` Kukjin Kim
1 sibling, 1 reply; 5+ messages in thread
From: Michał Nazarewicz @ 2010-09-28 13:01 UTC (permalink / raw)
To: linux-arm-kernel
On Tue, 28 Sep 2010 14:45:59 +0200, Sergei Shtylyov <sshtylyov@mvista.com> wrote:
> Hello.
>
> On 28-09-2010 5:31, Kukjin Kim wrote:
>
>> From: Changhwan Youn<chaos.youn@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@samsung.com>
>> Signed-off-by: Changhwan Youn<chaos.youn@samsung.com>
>> Signed-off-by: Kukjin Kim<kgene.kim@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...
__ffs than?
--
Best regards, _ _
| Humble Liege of Serenely Enlightened Majesty of o' \,=./ `o
| Computer Science, Micha? "mina86" Nazarewicz (o o)
+----[mina86*mina86.com]---[mina86*jabber.org]----ooO--(_)--Ooo--
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH] ARM: S5PV310: Optimize interrupt source searching code
2010-09-28 12:45 ` Sergei Shtylyov
2010-09-28 13:01 ` Michał Nazarewicz
@ 2010-09-28 13:10 ` Kukjin Kim
1 sibling, 0 replies; 5+ messages in thread
From: Kukjin Kim @ 2010-09-28 13:10 UTC (permalink / raw)
To: linux-arm-kernel
Sergei Shtylyov wrote:
>
> Hello.
>
Hi ;-)
> On 28-09-2010 5:31, Kukjin Kim wrote:
>
> > From: Changhwan Youn<chaos.youn@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@samsung.com>
> > Signed-off-by: Changhwan Youn<chaos.youn@samsung.com>
> > Signed-off-by: Kukjin Kim<kgene.kim@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...
>
Yes, you're right.
So I already re-submitted like following :-)
http://lists.infradead.org/pipermail/linux-arm-kernel/2010-September/027071.
html
Thanks for your pointing out.
Best regards,
Kgene.
--
Kukjin Kim <kgene.kim@samsung.com>, Senior Engineer,
SW Solution Development Team, Samsung Electronics Co., Ltd.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH] ARM: S5PV310: Optimize interrupt source searching code
2010-09-28 13:01 ` Michał Nazarewicz
@ 2010-09-28 14:07 ` Kukjin Kim
0 siblings, 0 replies; 5+ messages in thread
From: Kukjin Kim @ 2010-09-28 14:07 UTC (permalink / raw)
To: linux-arm-kernel
Michal Nazarewicz wrote:
>
Hi :-)
> On Tue, 28 Sep 2010 14:45:59 +0200, Sergei Shtylyov <sshtylyov@mvista.com>
> wrote:
>
> > Hello.
> >
> > On 28-09-2010 5:31, Kukjin Kim wrote:
> >
> >> From: Changhwan Youn<chaos.youn@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@samsung.com>
> >> Signed-off-by: Changhwan Youn<chaos.youn@samsung.com>
> >> Signed-off-by: Kukjin Kim<kgene.kim@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...
>
> __ffs than?
>
Yes, already re-submitted.
Thanks.
Best regards,
Kgene.
--
Kukjin Kim <kgene.kim@samsung.com>, Senior Engineer,
SW Solution Development Team, Samsung Electronics Co., Ltd.
^ permalink raw reply [flat|nested] 5+ messages in thread
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2010-09-28 1:31 [PATCH] ARM: S5PV310: Optimize interrupt source searching code Kukjin Kim
2010-09-28 12:45 ` Sergei Shtylyov
2010-09-28 13:01 ` Michał Nazarewicz
2010-09-28 14:07 ` Kukjin Kim
2010-09-28 13:10 ` Kukjin Kim
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