[Intel-gfx] [PATCH v4] drm/i915/pmu: Clear the previous sample value when parking

[Chris Wilson]

Quoting Tvrtko Ursulin (2017-11-23 10:26:54)
> From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> 
> When turning off the engines, and the pmu sampling, clear the previous
> value as the current measurement should be 0.
> 
> v2: Use a for-loop
> v3:
>  * Move clearing to timer self-dis-arm to avoid race with parking.
>  * Clear frequency samples as well.
> v4:
>  * Init frequency to idle_freq. (Chris Wilson)
> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> Suggested-by: Chris Wilson <chris at chris-wilson.co.uk>
> Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk> (v3)

Ok, we know we still have a hole if the timer is running for both
engine and frequency sampling at the time of parking, and we accept that
this is just a step in the right direction to reduce the small
statistical error.

Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris