Merge pull request #46 from toradex/4.9-2.3.x-imx

4.9 2.3.x imx

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index fd11be6b23b9..62bcc770a181 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -386,8 +386,13 @@ static u64 execlists_update_context(struct drm_i915_gem_request *rq)
 	 * may not be visible to the HW prior to the completion of the UC
 	 * register write and that we may begin execution from the context
 	 * before its image is complete leading to invalid PD chasing.
+	 *
+	 * Furthermore, Braswell, at least, wants a full mb to be sure that
+	 * the writes are coherent in memory (visible to the GPU) prior to
+	 * execution, and not just visible to other CPUs (as is the result of
+	 * wmb).
 	 */
-	wmb();
+	mb();
 	return ce->lrc_desc;
 }