[PATCH v4 2/6] drm/i915/gt: Ensure memory quiesced before invalidation

[Matt Roper]

On Tue, Jul 18, 2023 at 02:28:26AM +0200, Andi Shyti wrote:
> Hi Matt,
> 
> > > > > > +	/*
> > > > > > +	 * Aux invalidations on Aux CCS platforms require
> > > > > > +	 * memory traffic is quiesced prior.
> > > > > > +	 */
> > > > > > +	if ((mode & EMIT_INVALIDATE) && !HAS_FLAT_CCS(engine->i915))
> > > > > 
> > > > > It's a pre-existing mistake in drm-tip at the moment, but we shouldn't
> > > > > assume !flatccs always implies auxccs.  PVC has neither, and there may
> > > > > be other similar platforms in the future.  We should probably add a
> > > > > helper function for AuxCCS, similar to what we added to the Xe driver
> > > > > recently:
> > > > > 
> > > > > https://patchwork.freedesktop.org/patch/539304/?series=118334&rev=1
> > > 
> > > Currently that is done in patch 6...
> > 
> > Are you sure?  Patch #6 consolidates things a bit, but is still incorrectly
> > assuming flatccs = !auxccs:
> > 
> >        if (HAS_FLAT_CCS(engine->i915))                                                                                                            
> >                return _MMIO(0);                                                                                                                   
> 
> But isn't it the same the patch you linked is doing?
> 
> 	return !xe->info.has_flat_ccs;

No, that's just the end of the function.  The important
platform-specific checks come before that point (at the moment we only
have PVC, but we expect more platforms to be added there very soon too).


Matt

> 
> And

-- 
Matt Roper
Graphics Software Engineer
Linux GPU Platform Enablement
Intel Corporation