* [PATCH] clocksource: mips-gic-timer: fix clocksource counter width
@ 2018-02-21 12:47 Felix Fietkau
2018-02-28 8:56 ` Thomas Gleixner
0 siblings, 1 reply; 4+ messages in thread
From: Felix Fietkau @ 2018-02-21 12:47 UTC (permalink / raw)
To: linux-kernel; +Cc: tglx, daniel.lezcano, paul.burton
This code needs to use ffs instead of fls on the mask to determine the
shift for reading the GIC_CONFIG_COUNTBITS field.
Fixes: e07127a077c7 ("clocksource: mips-gic-timer: Use new GIC accessor functions")
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: stable@vger.kernel.org
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
drivers/clocksource/mips-gic-timer.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/clocksource/mips-gic-timer.c b/drivers/clocksource/mips-gic-timer.c
index a04808a21d4e..bf0eee78c6ef 100644
--- a/drivers/clocksource/mips-gic-timer.c
+++ b/drivers/clocksource/mips-gic-timer.c
@@ -166,7 +166,7 @@ static int __init __gic_clocksource_init(void)
/* Set clocksource mask. */
count_width = read_gic_config() & GIC_CONFIG_COUNTBITS;
- count_width >>= __fls(GIC_CONFIG_COUNTBITS);
+ count_width >>= __ffs(GIC_CONFIG_COUNTBITS);
count_width *= 4;
count_width += 32;
gic_clocksource.mask = CLOCKSOURCE_MASK(count_width);
--
2.14.2
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] clocksource: mips-gic-timer: fix clocksource counter width
2018-02-21 12:47 [PATCH] clocksource: mips-gic-timer: fix clocksource counter width Felix Fietkau
@ 2018-02-28 8:56 ` Thomas Gleixner
2018-02-28 9:19 ` Felix Fietkau
0 siblings, 1 reply; 4+ messages in thread
From: Thomas Gleixner @ 2018-02-28 8:56 UTC (permalink / raw)
To: Felix Fietkau; +Cc: linux-kernel, daniel.lezcano, paul.burton
On Wed, 21 Feb 2018, Felix Fietkau wrote:
> This code needs to use ffs instead of fls on the mask to determine the
> shift for reading the GIC_CONFIG_COUNTBITS field.
Why?
Thanks,
tglx
> Fixes: e07127a077c7 ("clocksource: mips-gic-timer: Use new GIC accessor functions")
> Cc: Paul Burton <paul.burton@imgtec.com>
> Cc: stable@vger.kernel.org
> Signed-off-by: Felix Fietkau <nbd@nbd.name>
> ---
> drivers/clocksource/mips-gic-timer.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/clocksource/mips-gic-timer.c b/drivers/clocksource/mips-gic-timer.c
> index a04808a21d4e..bf0eee78c6ef 100644
> --- a/drivers/clocksource/mips-gic-timer.c
> +++ b/drivers/clocksource/mips-gic-timer.c
> @@ -166,7 +166,7 @@ static int __init __gic_clocksource_init(void)
>
> /* Set clocksource mask. */
> count_width = read_gic_config() & GIC_CONFIG_COUNTBITS;
> - count_width >>= __fls(GIC_CONFIG_COUNTBITS);
> + count_width >>= __ffs(GIC_CONFIG_COUNTBITS);
> count_width *= 4;
> count_width += 32;
> gic_clocksource.mask = CLOCKSOURCE_MASK(count_width);
> --
> 2.14.2
>
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] clocksource: mips-gic-timer: fix clocksource counter width
2018-02-28 8:56 ` Thomas Gleixner
@ 2018-02-28 9:19 ` Felix Fietkau
2018-02-28 9:27 ` Thomas Gleixner
0 siblings, 1 reply; 4+ messages in thread
From: Felix Fietkau @ 2018-02-28 9:19 UTC (permalink / raw)
To: Thomas Gleixner; +Cc: linux-kernel, daniel.lezcano, paul.burton
On 2018-02-28 09:56, Thomas Gleixner wrote:
> On Wed, 21 Feb 2018, Felix Fietkau wrote:
>
>> This code needs to use ffs instead of fls on the mask to determine the
>> shift for reading the GIC_CONFIG_COUNTBITS field.
>
> Why?
>> count_width = read_gic_config() & GIC_CONFIG_COUNTBITS;
>> - count_width >>= __fls(GIC_CONFIG_COUNTBITS);
>> + count_width >>= __ffs(GIC_CONFIG_COUNTBITS);
This code is trying to extract the GIC_CONFIG_COUNTBITS field from
read_gic_config(), so it needs to shift count_width right by the index
of the least significant bit (__ffs) instead of the most significant bit
(__fls) of the field mask.
- Felix
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] clocksource: mips-gic-timer: fix clocksource counter width
2018-02-28 9:19 ` Felix Fietkau
@ 2018-02-28 9:27 ` Thomas Gleixner
0 siblings, 0 replies; 4+ messages in thread
From: Thomas Gleixner @ 2018-02-28 9:27 UTC (permalink / raw)
To: Felix Fietkau; +Cc: linux-kernel, daniel.lezcano, paul.burton
On Wed, 28 Feb 2018, Felix Fietkau wrote:
> On 2018-02-28 09:56, Thomas Gleixner wrote:
> > On Wed, 21 Feb 2018, Felix Fietkau wrote:
> >
> >> This code needs to use ffs instead of fls on the mask to determine the
> >> shift for reading the GIC_CONFIG_COUNTBITS field.
> >
> > Why?
> >> count_width = read_gic_config() & GIC_CONFIG_COUNTBITS;
> >> - count_width >>= __fls(GIC_CONFIG_COUNTBITS);
> >> + count_width >>= __ffs(GIC_CONFIG_COUNTBITS);
> This code is trying to extract the GIC_CONFIG_COUNTBITS field from
> read_gic_config(), so it needs to shift count_width right by the index
> of the least significant bit (__ffs) instead of the most significant bit
> (__fls) of the field mask.
Sure, but that information wants to be in the changelog.
Thanks,
tglx
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2018-02-28 9:26 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2018-02-21 12:47 [PATCH] clocksource: mips-gic-timer: fix clocksource counter width Felix Fietkau
2018-02-28 8:56 ` Thomas Gleixner
2018-02-28 9:19 ` Felix Fietkau
2018-02-28 9:27 ` Thomas Gleixner
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