[RFC 8/9] drm/i915: Lift the user PAT restriction from use_cpu_reloc

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Now that i915 understands the caching modes behind PAT indices, we can
refine the check in use_cpu_reloc() to not reject the uncached PAT if it
was set by userspace.

Instead it can decide based on the presence of full coherency which
should be functionally equivalent on legacy platforms. We can ignore WT
since it is only used by the display, and we can ignore Meteorlake since
it will fail on the existing "has_llc" condition before the object cache
mode check.

v2:
 * Try I915_BO_CACHE_COHERENT_FOR_WRITE as criteria.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Cc: Fei Yang <fei.yang at intel.com>
Cc: Matt Roper <matthew.d.roper at intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index 9d6e49c8a4c6..ab3fa5263560 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -640,16 +640,9 @@ static inline int use_cpu_reloc(const struct reloc_cache *cache,
 	if (DBG_FORCE_RELOC == FORCE_GTT_RELOC)
 		return false;
 
-	/*
-	 * For objects created by userspace through GEM_CREATE with pat_index
-	 * set by set_pat extension, i915_gem_object_has_cache_level() always
-	 * return true, otherwise the call would fall back to checking whether
-	 * the object is un-cached.
-	 */
 	return (cache->has_llc ||
 		obj->cache_dirty ||
-		!(obj->pat_set_by_user ||
-		  i915_gem_object_has_cache_mode(obj, I915_CACHE_MODE_UC)));
+		(obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_WRITE));
 }
 
 static int eb_reserve_vma(struct i915_execbuffer *eb,
-- 
2.39.2