[PATCH 02/13] drm/i915: Do not clflush snooped objects

Chris Wilson
2011-04-14T09:04:04Z

Rely on the GPU snooping into the CPU cache for appropriately bound
objects on MI_FLUSH. Or perhaps one day we will have a cache-coherent
CPU/GPU package...

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
drivers/gpu/drm/i915/i915_gem.c | 11 +++++++++++
1 files changed, 11 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 264bec8..bf32527 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2878,6 +2878,17 @@ i915_gem_clflush_object(struct drm_i915_gem_object *obj)
if (obj->pages == NULL)
return;

+ /* If the GPU is snooping the contents of the CPU cache,
+ * we do not need to manually clear the CPU cache lines. However,
+ * the caches are only snooped when the render cache is
+ * flushed/invalidated. As we always have to emit invalidations
+ * and flushes when moving into and out of the RENDER domain, correct
+ * snooping behaviour occurs naturally as the result of our domain
+ * tracking.
+ */
+ if (obj->cache_level != I915_CACHE_NONE)
+ return;
+
trace_i915_gem_object_clflush(obj);

drm_clflush_pages(obj->pages, obj->base.size / PAGE_SIZE);
--
1.7.4.1