Re: [PATCH v2 2/2] drm/i915/gt: Enable only one CCS for compute workload

[Andi Shyti <andi.shyti@linux.intel.com>]

Hi Tvrtko,

On Tue, Feb 20, 2024 at 02:48:31PM +0000, Tvrtko Ursulin wrote:
> On 20/02/2024 14:35, Andi Shyti wrote:
> > Enable only one CCS engine by default with all the compute sices
> 
> slices

Thanks!

> > diff --git a/drivers/gpu/drm/i915/gt/intel_engine_user.c b/drivers/gpu/drm/i915/gt/intel_engine_user.c
> > index 833987015b8b..7041acc77810 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_engine_user.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_engine_user.c
> > @@ -243,6 +243,15 @@ void intel_engines_driver_register(struct drm_i915_private *i915)
> >   		if (engine->uabi_class == I915_NO_UABI_CLASS)
> >   			continue;
> > +		/*
> > +		 * Do not list and do not count CCS engines other than the first
> > +		 */
> > +		if (engine->uabi_class == I915_ENGINE_CLASS_COMPUTE &&
> > +		    engine->uabi_instance > 0) {
> > +			i915->engine_uabi_class_count[engine->uabi_class]--;
> > +			continue;
> > +		}
> 
> It's a bit ugly to decrement after increment, instead of somehow
> restructuring the loop to satisfy both cases more elegantly.

yes, agree, indeed I had a hard time here to accept this change
myself.

But moving the check above where the counter was incremented it
would have been much uglier.

This check looks ugly everywhere you place it :-)

In any case, I'm working on a patch that is splitting this
function in two parts and there is some refactoring happening
here (for the first initialization and the dynamic update).

Please let me know if it's OK with you or you want me to fix it
in this run.

> And I wonder if
> internally (in dmesg when engine name is logged) we don't end up with ccs0
> ccs0 ccs0 ccs0.. for all instances.

I don't see this. Even in sysfs we see only one ccs. Where is it?

> > +
> >   		rb_link_node(&engine->uabi_node, prev, p);
> >   		rb_insert_color(&engine->uabi_node, &i915->uabi_engines);

[...]

> > diff --git a/drivers/gpu/drm/i915/i915_query.c b/drivers/gpu/drm/i915/i915_query.c
> > index 3baa2f54a86e..d5a5143971f5 100644
> > --- a/drivers/gpu/drm/i915/i915_query.c
> > +++ b/drivers/gpu/drm/i915/i915_query.c
> > @@ -124,6 +124,7 @@ static int query_geometry_subslices(struct drm_i915_private *i915,
> >   	return fill_topology_info(sseu, query_item, sseu->geometry_subslice_mask);
> >   }
> > +
> 
> Zap please.

yes... yes... I noticed it after sending the patch :-)

Thanks,
Andi