[PATCH 14/14] drm/i915: Avoid underruns when disabling sprites

[ville.syrjala@linux.intel.com]

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

As the watermark registers aren't double bufferd, clearing the
watermarks immediately after writing the sprite registers can be
hazardous.

Until we have something better, add a wait for vblank between the
two steps to make sure the sprite no longer needs the watermark
levels before we clear them.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_sprite.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_sprite.c b/drivers/gpu/drm/i915/intel_sprite.c
index a872129..fe4de89 100644
--- a/drivers/gpu/drm/i915/intel_sprite.c
+++ b/drivers/gpu/drm/i915/intel_sprite.c
@@ -336,6 +336,12 @@ ivb_disable_plane(struct drm_plane *plane, struct drm_crtc *crtc)
 	I915_MODIFY_DISPBASE(SPRSURF(pipe), 0);
 	POSTING_READ(SPRSURF(pipe));
 
+	/*
+	 * Avoid underruns when disabling the sprite.
+	 * FIXME remove once watermark updates are done properly.
+	 */
+	intel_wait_for_vblank(dev, pipe);
+
 	intel_update_sprite_watermarks(plane, crtc, 0, 0, false, false);
 }
 
@@ -503,6 +509,12 @@ ilk_disable_plane(struct drm_plane *plane, struct drm_crtc *crtc)
 	I915_MODIFY_DISPBASE(DVSSURF(pipe), 0);
 	POSTING_READ(DVSSURF(pipe));
 
+	/*
+	 * Avoid underruns when disabling the sprite.
+	 * FIXME remove once watermark updates are done properly.
+	 */
+	intel_wait_for_vblank(dev, pipe);
+
 	intel_update_sprite_watermarks(plane, crtc, 0, 0, false, false);
 }
 
-- 
1.8.3.2

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