[Intel-gfx] [PATCH 2/2] drm/i915: use semaphores for the display plane

[Ben Widawsky]

In theory this will have performance and power improvements. Performance
because we don't need to stall when the scanout BO is busy, and power
because we don't have to stall when the BO is busy ie. we can get the
work done sooner and put the CPU to sleep (and one less interrupt
required).

Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
---
 drivers/gpu/drm/i915/i915_gem.c |    8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index ce2fee5..96ad162 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3041,9 +3041,7 @@ int i915_gem_object_set_cache_level(struct drm_i915_gem_object *obj,
  * any flushes to be pipelined (for pageflips).
  *
  * For the display plane, we want to be in the GTT but out of any write
- * domains. So in many ways this looks like set_to_gtt_domain() apart from the
- * ability to pipeline the waits, pinning and any additional subtleties
- * that may differentiate the display plane from ordinary buffers.
+ * domains. So in many ways this looks like set_to_gtt_domain().
  */
 int
 i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
@@ -3058,8 +3056,8 @@ i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
 		return ret;
 
 	if (pipelined != obj->ring) {
-		ret = i915_gem_object_wait_rendering(obj);
-		if (ret == -ERESTARTSYS)
+		ret = i915_gem_object_sync(obj, pipelined);
+		if (ret)
 			return ret;
 	}
 
-- 
1.7.9.4