[PATCH] drm/i915: implement Disable4x2SubspanOptimization w/a for ivb, too

[Daniel Vetter <daniel.vetter@ffwll.ch>]

Copy&pasted from the vlv setup code. According to docs, we need that
on ivb, too.

Cc: Ben Widawsky <ben@bwidawsk.net>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
 drivers/gpu/drm/i915/intel_display.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 33aaad3..7be1d1a 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -8938,6 +8938,11 @@ static void ivybridge_init_clock_gating(struct drm_device *dev)
 			   DISPPLANE_TRICKLE_FEED_DISABLE);
 		intel_flush_display_plane(dev_priv, pipe);
 	}
+
+	/* WaDisable4x2SubspanOptimization */
+	I915_WRITE(CACHE_MODE_1, I915_READ(CACHE_MODE_1) |
+		   (PIXEL_SUBSPAN_COLLECT_OPT_DISABLE << 16) |
+		   PIXEL_SUBSPAN_COLLECT_OPT_DISABLE);
 }
 
 static void valleyview_init_clock_gating(struct drm_device *dev)
-- 
1.7.10