[PATCH] at91: cpuidle: Fix target_residency

[daniel.lezcano@linaro.org (Daniel Lezcano)]

On 06/21/2013 04:48 PM, Nicolas Ferre wrote:
> On 21/06/2013 15:22, Daniel Lezcano :
>> On 06/21/2013 03:20 PM, Nicolas Ferre wrote:
>>> On 21/06/2013 14:36, Daniel Lezcano :
>>>> The following commit:
>>>>
>>>> commit 7e348b9012522fa0efd854d20d210d5e57fcedd1
>>>> Author: Robert Lee <rob.lee@linaro.org>
>>>> Date:   Tue Mar 20 15:22:43 2012 -0500
>>>>
>>>>       ARM: at91: Consolidate time keeping and irq enable
>>>>
>>>>       Enable core cpuidle timekeeping and irq enabling and remove that
>>>>       handling from this code.
>>>>
>>>> introduced a zero to the state1 (suspend) target residency.
>>>>
>>>> [ ... ]
>>>>
>>>> +       .states[1]              = {
>>>> +               .enter                  = at91_enter_idle,
>>>> +               .exit_latency           = 10,
>>>> +               .target_residency       = 100000,
>>>> +               .flags                  = CPUIDLE_FLAG_TIME_VALID,
>>>> +               .name                   = "RAM_SR",
>>>> +               .desc                   = "WFI and DDR Self Refresh",
>>>> +       },
>>>>
>>>> [ ... ]
>>>>
>>>> -       /* Wait for interrupt and RAM self refresh state */
>>>> -       driver->states[1].enter = at91_enter_idle;
>>>> -       driver->states[1].exit_latency = 10;
>>>> -       driver->states[1].target_residency = 10000;
>>>> -       driver->states[1].flags = CPUIDLE_FLAG_TIME_VALID;
>>>> -       strcpy(driver->states[1].name, "RAM_SR");
>>>> -       strcpy(driver->states[1].desc, "WFI and RAM Self Refresh");
>>>>
>>>> [ ... ]
>>>>
>>>> The cpuidle never enters this state since this commit.
>>
>> To be a bit more precise. With a periodic tick, the cpu never enters the
>> state1 with both 10000 and 100000.
>>
>> With a tickless system, it enters to state1 much more often with the
>> initial value, roughly x7 more.
> 
> BTW Daniel, I think I can stack this patch on my fixes-non-critical
> branch for 3.11: do you think that I should push for making it accepted
> for 3.10 (even if it seems very late)?

Yes, I think it should go for 3.10 as it is fix and also for 3.9.8
(stable). May be I should have Cc stable@ ...


>> BTW, I am surpised with a sam926*, CONFIG_NO_HZ=y is not in the default
>> config.
> 
> Yes, indeed: we have to consider it.
> 
> Best regards,
> 
>>>> Fix it by setting the value to 10ms again.
>>>>
>>>> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
>>>
>>> Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
>>>
>>>> ---
>>>>    arch/arm/mach-at91/cpuidle.c |    2 +-
>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/arch/arm/mach-at91/cpuidle.c
>>>> b/arch/arm/mach-at91/cpuidle.c
>>>> index 69f9e3b..4ec6a6d 100644
>>>> --- a/arch/arm/mach-at91/cpuidle.c
>>>> +++ b/arch/arm/mach-at91/cpuidle.c
>>>> @@ -51,7 +51,7 @@ static struct cpuidle_driver at91_idle_driver = {
>>>>        .states[1]        = {
>>>>            .enter            = at91_enter_idle,
>>>>            .exit_latency        = 10,
>>>> -        .target_residency    = 100000,
>>>> +        .target_residency    = 10000,
>>>>            .flags            = CPUIDLE_FLAG_TIME_VALID,
>>>>            .name            = "RAM_SR",
>>>>            .desc            = "WFI and DDR Self Refresh",
>>>>
>>>
>>>
>>
>>
> 
> 


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