Re: [PATCH v2] drm/i915/selftests: Add delay to stabilize frequency in live_rps_power

["Anirban, Sk" <sk.anirban@intel.com>]

On 03-12-2024 16:16, Jani Nikula wrote:
> On Tue, 03 Dec 2024, Sk Anirban <sk.anirban@intel.com> wrote:
>> Add delays to allow frequency stabilization before power measurement
>> to fix sporadic power conservation issues in live_rps_power test.
> Looks like band-aid. What's the root cause?
>
> BR,
> Jani.

In some cases, we have observed that the power consumption at the 
minimum frequency is greater than at the maximum frequency. This is 
likely due to the actual frequency not settling. The issue is sporadic, 
and to address this, we are adding a delay after setting the freq and 
before measuring the power.

Thanks,
Anirban

>> v2:
>>    - Move delay to respective function (Badal)
>>
>> Signed-off-by: Sk Anirban <sk.anirban@intel.com>
>> ---
>>   drivers/gpu/drm/i915/gt/selftest_rps.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/gpu/drm/i915/gt/selftest_rps.c b/drivers/gpu/drm/i915/gt/selftest_rps.c
>> index dcef8d498919..c207a4fb03bf 100644
>> --- a/drivers/gpu/drm/i915/gt/selftest_rps.c
>> +++ b/drivers/gpu/drm/i915/gt/selftest_rps.c
>> @@ -1125,6 +1125,7 @@ static u64 measure_power(struct intel_rps *rps, int *freq)
>>   static u64 measure_power_at(struct intel_rps *rps, int *freq)
>>   {
>>   	*freq = rps_set_check(rps, *freq);
>> +	msleep(100);
>>   	return measure_power(rps, freq);
>>   }