[Intel-gfx] [PATCH] drm/i915: Clear any existing dither mode prior to enabling spatial dithering

Chris Wilson chris at chris-wilson.co.uk
Mon Jul 26 00:09:13 CEST 2010

We cannot the initial configuration set by the BIOS not to have a dither
mode enabled which conflicts with our enabling the Spatial Temporal 1
dither mode for PCH. In particular, the BIOS may either enable temporal
dithering or the Spatial Temporal 2 with the result that we enable pure
temporal dithering. Temporal dithering looks bad and is perceived as a


  Bug 29248 - [Arrandale] Annoying flicker on internal panel, goes away
              after suspend to RAM

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
 drivers/gpu/drm/i915/intel_display.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 7133436..fb6568b 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -3925,6 +3925,7 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
 			if (dev_priv->lvds_dither) {
 				if (HAS_PCH_SPLIT(dev)) {
 					pipeconf |= PIPE_ENABLE_DITHER;
+					pipeconf &= ~PIPE_DITHER_TYPE_MASK;
 					pipeconf |= PIPE_DITHER_TYPE_ST01;
 				} else
 					lvds |= LVDS_ENABLE_DITHER;

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