[PATCH 4.4 220/342] drm/i915: Make sure DC writes are coherent on flush.

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Francisco Jerez <redacted>

commit 935a0ff0e1ea62a116848c0a187b13838f7b9cee upstream.

We need to set the DC FLUSH PIPE_CONTROL bit on Gen7+ to guarantee
that writes performed via the HDC are visible in memory.  Fixes an
intermittent failure in a Piglit test that writes to a BO from a
shader using GL atomic counters (implemented as HDC untyped atomics)
and then expects the memory to read back the same value after mapping
it on the CPU.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91298
Tested-by: Mark Janes <redacted>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Francisco Jerez <redacted>
Reviewed-by: Ville Syrjälä <redacted>
Link: http://patchwork.freedesktop.org/patch/msgid/1452740379-3194-1-git-send-email-currojerez@riseup.net
(cherry picked from commit 965fd602a6436f689f4f2fe40a6789582778ccd5)
Signed-off-by: Jani Nikula <redacted>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/gpu/drm/i915/intel_lrc.c        |    1 +
 drivers/gpu/drm/i915/intel_ringbuffer.c |    2 ++
 2 files changed, 3 insertions(+)

--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c

@@ -1706,6 +1706,7 @@ static int gen8_emit_flush_render(struct
 	if (flush_domains) {
 		flags |= PIPE_CONTROL_RENDER_TARGET_CACHE_FLUSH;
 		flags |= PIPE_CONTROL_DEPTH_CACHE_FLUSH;
+		flags |= PIPE_CONTROL_DC_FLUSH_ENABLE;
 		flags |= PIPE_CONTROL_FLUSH_ENABLE;
 	}
 
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -347,6 +347,7 @@ gen7_render_ring_flush(struct drm_i915_g
 	if (flush_domains) {
 		flags |= PIPE_CONTROL_RENDER_TARGET_CACHE_FLUSH;
 		flags |= PIPE_CONTROL_DEPTH_CACHE_FLUSH;
+		flags |= PIPE_CONTROL_DC_FLUSH_ENABLE;
 		flags |= PIPE_CONTROL_FLUSH_ENABLE;
 	}
 	if (invalidate_domains) {

@@ -419,6 +420,7 @@ gen8_render_ring_flush(struct drm_i915_g
 	if (flush_domains) {
 		flags |= PIPE_CONTROL_RENDER_TARGET_CACHE_FLUSH;
 		flags |= PIPE_CONTROL_DEPTH_CACHE_FLUSH;
+		flags |= PIPE_CONTROL_DC_FLUSH_ENABLE;
 		flags |= PIPE_CONTROL_FLUSH_ENABLE;
 	}
 	if (invalidate_domains) {