[Intel-gfx] [PATCH] drm/i915: Use spatio-temporal dithering on PCH

[Adam Jackson]

Spatial dither is better than nothing, but ST is even better.

Signed-off-by: Adam Jackson <ajax at redhat.com>
---
 drivers/gpu/drm/i915/i915_reg.h      |    5 ++++-
 drivers/gpu/drm/i915/intel_display.c |   10 ++++++----
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 527d30a..0bbbb77 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -1922,7 +1922,10 @@
 /* Display & cursor control */
 
 /* dithering flag on Ironlake */
-#define PIPE_ENABLE_DITHER	(1 << 4)
+#define PIPE_ENABLE_DITHER		(1 << 4)
+#define PIPE_DITHER_TYPE_MASK		(3 << 2)
+#define PIPE_DITHER_TYPE_SPATIAL	(0 << 2)
+#define PIPE_DITHER_TYPE_ST01		(1 << 2)
 /* Pipe A */
 #define PIPEADSL		0x70000
 #define PIPEACONF		0x70008
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 58668c4..36ead0e 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -3676,14 +3676,16 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
 		/* set the dithering flag */
 		if (IS_I965G(dev)) {
 			if (dev_priv->lvds_dither) {
-				if (HAS_PCH_SPLIT(dev))
+				if (HAS_PCH_SPLIT(dev)) {
 					pipeconf |= PIPE_ENABLE_DITHER;
-				else
+					pipeconf |= PIPE_DITHER_TYPE_ST01;
+				} else
 					lvds |= LVDS_ENABLE_DITHER;
 			} else {
-				if (HAS_PCH_SPLIT(dev))
+				if (HAS_PCH_SPLIT(dev)) {
 					pipeconf &= ~PIPE_ENABLE_DITHER;
-				else
+					pipeconf &= ~PIPE_DITHER_TYPE_MASK;
+				} else
 					lvds &= ~LVDS_ENABLE_DITHER;
 			}
 		}
-- 
1.7.0.1