drm/i915: Clear the Ironlake dithering flags when the pipe doesn't wa…

…nt 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>

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);