Re: [Intel-gfx] [PATCH 5/9] drm/i915/pmu: Prepare for multi-tile non-engine counters

["Dixit, Ashutosh" <ashutosh.dixit@intel.com>]

On Thu, 30 Mar 2023 05:39:04 -0700, Tvrtko Ursulin wrote:
>

Hi Tvrtko,

> > diff --git a/drivers/gpu/drm/i915/i915_pmu.h b/drivers/gpu/drm/i915/i915_pmu.h
> > index 1b04c79907e8..a708e44a227e 100644
> > --- a/drivers/gpu/drm/i915/i915_pmu.h
> > +++ b/drivers/gpu/drm/i915/i915_pmu.h
> > @@ -38,13 +38,16 @@ enum {
> >	__I915_NUM_PMU_SAMPLERS
> >   };
> >   +#define I915_PMU_MAX_GTS (4) /* FIXME */
>
> 3-4 years since writing this I have no idea what I meant by this
> FIXME. Should have put a better comment.. :( It was early platform
> enablement times so it was somewhat passable, but now I think we need to
> figure out what I actually meant. Maybe removing the comment is fine.
>
> > diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
> > index dba7c5a5b25e..bbab7f3dbeb4 100644
> > --- a/include/uapi/drm/i915_drm.h
> > +++ b/include/uapi/drm/i915_drm.h
> > @@ -280,7 +280,17 @@ enum drm_i915_pmu_engine_sample {
> >   #define I915_PMU_ENGINE_SEMA(class, instance) \
> >	__I915_PMU_ENGINE(class, instance, I915_SAMPLE_SEMA)
> >   -#define __I915_PMU_OTHER(x) (__I915_PMU_ENGINE(0xff, 0xff, 0xf) + 1 +
> > (x))
> > +/*
> > + * Top 8 bits of every non-engine counter are GT id.
> > + * FIXME: __I915_PMU_GT_SHIFT will be changed to 56
> > + */
>
> I asked before and don't think I got an answer: Why is 4 bits not enough
> for gt id? The comment is not my code I am pretty sure.

Both of the above FIXME's are the work of yours truly :-) (added during
PRELIM work).

Anyway given that now i915 will not support new product generations I think
we can just drop the FIXME's. Otherwise I was saying since we are only
using a few bottom bits, why not future proof things a bit and allow for
num_gt's to expand beyond 16.

So for now just drop the FIXME's for i915, revisit if needed with xe.

Thanks.
--
Ashutosh