[Intel-gfx] [PATCH] drm/i915/pmu: Do not report 100% RC6 if not supported

[Rodrigo Vivi]

On Tue, Mar 30, 2021 at 04:06:37PM +0100, Tvrtko Ursulin wrote:
> From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> 
> We use GT parked status to estimate RC6 while not in use, however if RC6
> is not supported to start with that does not work very well and produces a
> false 100% RC6 readout.

oh! I had missed this one...

> 
> Fix by not advancing the estimated RC6 counter when feature is not
> supported.

either this or the other proposal, consider both as

Reviewed-by: Rodrigo Vivi <rodrigo.vivi at intel.com>

I prefer this, but I don't have strong opinions on which one.
you (or Eero) pick one...

> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> Fixes: 1fe699e30113 ("drm/i915/pmu: Fix sleep under atomic in RC6 readout")
> Reported-by: Eero T Tamminen <eero.t.tamminen at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_pmu.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_pmu.c b/drivers/gpu/drm/i915/i915_pmu.c
> index 41651ac255fa..02fe0d22c470 100644
> --- a/drivers/gpu/drm/i915/i915_pmu.c
> +++ b/drivers/gpu/drm/i915/i915_pmu.c
> @@ -191,7 +191,10 @@ static u64 get_rc6(struct intel_gt *gt)
>  		 * on top of the last known real value, as the approximated RC6
>  		 * counter value.
>  		 */
> -		val = ktime_since_raw(pmu->sleep_last);
> +		if (gt->rc6.supported)
> +			val = ktime_since_raw(pmu->sleep_last);
> +		else
> +			val = 0;
>  		val += pmu->sample[__I915_SAMPLE_RC6].cur;
>  	}
>  
> -- 
> 2.27.0
> 
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