drm/i915: Clear the Ironlake dithering flags when the pipe doesn't want it.

My fine DisplayPort output was getting ST dithering forever after
having had the LVDS enabled at one point.

Signed-off-by: Eric Anholt <eric@anholt.net>

1 files changed, 7 insertions, 5 deletions

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index ca3b8a8933c6..ae1718549eec 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -3888,6 +3888,11 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
                 udelay(150);
         }
 
+        if (HAS_PCH_SPLIT(dev)) {
+                pipeconf &= ~PIPE_ENABLE_DITHER;
+                pipeconf &= ~PIPE_DITHER_TYPE_MASK;
+        }
+
         /* The LVDS pin pair needs to be on before the DPLLs are enabled.
          * This is an exception to the general rule that mode_set doesn't turn
          * things on.
@@ -3930,16 +3935,13 @@ 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;
                         } else {
-                                if (HAS_PCH_SPLIT(dev)) {
-                                        pipeconf &= ~PIPE_ENABLE_DITHER;
-                                        pipeconf &= ~PIPE_DITHER_TYPE_MASK;
-                                } else
+                                if (!HAS_PCH_SPLIT(dev)) {
                                         lvds &= ~LVDS_ENABLE_DITHER;
+                                }
                         }
                 }
                 I915_WRITE(lvds_reg, lvds);