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

From: Andi Shyti <andi.shyti@intel.com>
To: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Intel-gfx@lists.freedesktop.org,
	Eero T Tamminen <eero.t.tamminen@intel.com>,
	dri-devel@lists.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH] drm/i915/pmu: Do not report 100% RC6 if not supported
Date: Tue, 6 Apr 2021 14:19:56 +0300	[thread overview]
Message-ID: <YGxD3HZEZ1hoV7gj@intel.intel> (raw)
In-Reply-To: <20210330150637.2547762-1-tvrtko.ursulin@linux.intel.com>

Hi Tvrtko,

> 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.
> 
> Fix by not advancing the estimated RC6 counter when feature is not
> supported.
> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Fixes: 1fe699e30113 ("drm/i915/pmu: Fix sleep under atomic in RC6 readout")
> Reported-by: Eero T Tamminen <eero.t.tamminen@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;

if rc6 is not supported, why are we here?

Did you mean rc6.enabled ?

Andi
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