[PATCH] at91: cpuidle: Fix target_residency

[daniel.lezcano@linaro.org (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, I am surpised with a sam926*, CONFIG_NO_HZ=y is not in the default
config.

>> 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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