> From: Tvrtko Ursulin <tvrtko.ursu...@intel.com> > > On Meteorlake CPU cache will not contain stale data after GPU > access since write-invalidate protocol is used, which means > there is no need to flush before potentially transitioning the > buffer to a non-coherent domain. > > Use the opportunity to documet the situation on discrete too.
LGTM. Reviewed-by: Fei Yang <fei.y...@intel.com> > Signed-off-by: Tvrtko Ursulin <tvrtko.ursu...@intel.com> > Cc: Matt Roper <matthew.d.ro...@intel.com> > Cc: Fei Yang <fei.y...@intel.com> > Cc: Matthew Auld <matthew.a...@intel.com> > Cc: Thomas Hellström <thomas.hellst...@linux.intel.com> > --- > drivers/gpu/drm/i915/gem/i915_gem_domain.c | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_domain.c > b/drivers/gpu/drm/i915/gem/i915_gem_domain.c > index ffddec1d2a76..57db9c581bf6 100644 > --- a/drivers/gpu/drm/i915/gem/i915_gem_domain.c > +++ b/drivers/gpu/drm/i915/gem/i915_gem_domain.c > @@ -24,9 +24,22 @@ static bool gpu_write_needs_clflush(struct > drm_i915_gem_object *obj) { > struct drm_i915_private *i915 = to_i915(obj->base.dev); > > + /* > + * Discrete GPUs never dirty the CPU cache. > + */ > if (IS_DGFX(i915)) > return false; > > + /* > + * Cache snooping on Meteorlake is using write-invalidate so GPU writes > + * never end up in the CPU cache. > + * > + * QQQ: Do other snooping platforms behave identicaly and could we > + * therefore write this as "if !HAS_LLC(i915) && HAS_SNOOP(i915)"? > + */ > + if (IS_METEORLAKE(i915)) > + return false; > + > /* > * For objects created by userspace through GEM_CREATE with pat_index > * set by set_pat extension, i915_gem_object_has_cache_level() will > -- > 2.39.2