[Intel-gfx] [PATCH 1/1] drm/i915/skl: fix RC6 residency time calculation

[Kamble, Sagar A]

Ok. I related my change to below definition:

#define GT_INTERVAL_FROM_US(dev_priv, us) (IS_GEN9(dev_priv) ? \
                                 (IS_BROXTON(dev_priv) ? \
                                 INTERVAL_0_833_US(us) : \
                                 INTERVAL_1_33_US(us)) : \
                                 INTERVAL_1_28_US(us))

This is using 1.33us unit for SKL.
May be we need to define these based on mode (normal/PSMI).
Not sure how to determine modes.

Thanks
Sagar


On 2/3/2016 10:40 PM, Imre Deak wrote:
> On ke, 2016-02-03 at 11:29 +0530, Sagar Arun Kamble wrote:
>> The RC6 residency time unit is 1.33us on SKL according to the
>> specification, so update the calculation accordingly.
>>
>> Cc: Imre Deak <imre.deak at intel.com>
>> Signed-off-by: Sagar Arun Kamble <sagar.a.kamble at intel.com>
>> ---
>>   drivers/gpu/drm/i915/i915_sysfs.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/i915/i915_sysfs.c
>> b/drivers/gpu/drm/i915/i915_sysfs.c
>> index c6188dd..9aa49a9 100644
>> --- a/drivers/gpu/drm/i915/i915_sysfs.c
>> +++ b/drivers/gpu/drm/i915/i915_sysfs.c
>> @@ -58,7 +58,8 @@ static u32 calc_residency(struct drm_device *dev,
>>   	} else if (IS_BROXTON(dev)) {
>>   		units = 1;
>>   		div = 1200;		/* 833.33ns */
>> -	}
>> +	} else if (IS_SKYLAKE(dev))
>> +		units = 133ULL;
> Hrm. The SKL/GT_GFX_RC6 description in ConfigDB doesn't say anything
> about the units, the BSpec "Timestamp Bases" provides two values for
> two different modes:
>
> 1.33us and 1.28us
>
> Not sure what are these different modes.
>
> BSpec GT_GFX_RC6 description specifies 1.28us.
>
> Running igt/pm_rc6_residency calculating with the current 1.28us results in:
> Residency in rc6 or deeper state: 2983 ms (sleep duration 3003 ms) (ratio to expected duration: 0,99)
> Subtest rc6-accuracy: SUCCESS (0,000s)
>
> and after applying your patch (calculating with 1.33us):
> Residency in rc6 or deeper state: 3101 ms (sleep duration 3001 ms) (ratio to expected duration: 1,03)
> (pm_rc6_residency:6281) CRITICAL: Test assertion failure function residency_accuracy, file pm_rc6_residency.c:110:
> (pm_rc6_residency:6281) CRITICAL: Failed assertion: ratio > 0.9 && ratio <= 1
> (pm_rc6_residency:6281) CRITICAL: Sysfs RC6 residency counter is inaccurate.
>
> While the measurement can be inaccurate, normally we should only err by
> measuring less duration in RC6 than the duration of the actual sleep.
> So I'm not convinced that 1.33us is the correct value..
>
> --Imre
>
>>   
>>   	raw_time = I915_READ(reg) * units;
>>   	ret = DIV_ROUND_UP_ULL(raw_time, div);