[PATCH 3/5] drm/i915/gt: Split the gen7 rcs flush into phases

[Chris Wilson]

We want to be sure that the memory is coherent prior to writing to the
breadcrumb. This should be guaranteed by the post-sync operation, but
for that little bit of extra paranoia, split the flush into two and have
the breadcrumb write separate and explicitly wait on the prior
pipecontrol completion.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/gt/intel_ring_submission.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_ring_submission.c b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
index 630fb9dc8b11..54497110a484 100644
--- a/drivers/gpu/drm/i915/gt/intel_ring_submission.c
+++ b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
@@ -410,8 +410,12 @@ static u32 *gen7_rcs_emit_breadcrumb(struct i915_request *rq, u32 *cs)
 	*cs++ = GFX_OP_PIPE_CONTROL(4);
 	*cs++ = (PIPE_CONTROL_RENDER_TARGET_CACHE_FLUSH |
 		 PIPE_CONTROL_DEPTH_CACHE_FLUSH |
-		 PIPE_CONTROL_DC_FLUSH_ENABLE |
-		 PIPE_CONTROL_FLUSH_ENABLE |
+		 PIPE_CONTROL_DC_FLUSH_ENABLE);
+	*cs++ = 0;
+	*cs++ = 0;
+
+	*cs++ = GFX_OP_PIPE_CONTROL(4);
+	*cs++ = (PIPE_CONTROL_FLUSH_ENABLE |
 		 PIPE_CONTROL_QW_WRITE |
 		 PIPE_CONTROL_GLOBAL_GTT_IVB |
 		 PIPE_CONTROL_CS_STALL);
-- 
2.25.1