[BISECTED, -next] drm/i915: blurred HDMI output

[Arnd Bergmann <arnd@arndb.de>]

Commit e9e331a8ab "drm/i915/lvds: Ensure panel is unlocked for Ironlake or
the panel fitter" broke my HDMI output on GMA4500HD, it seemed to be driving
the output with the wrong resolution, while still showing the native panel
resolution of 1680x1050 being in use. This caused a very irritating blur
on the screen.

After bisecting the problem, I managed to do a partial revert which fixes
the problem and applies on top of linux-next. I have no idea what this patch
actually does or if it can break any other configuration, but it solves the
problem for me.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 9109c00..2d47161 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -3921,6 +3921,10 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
 	pipeconf |= PIPECONF_ENABLE;
 	dpll |= DPLL_VCO_ENABLE;
 
+	/* Disable the panel fitter if it was on our pipe */
+	if (!HAS_PCH_SPLIT(dev) && intel_panel_fitter_pipe(dev) == pipe)
+		I915_WRITE(PFIT_CONTROL, 0);
+
 	DRM_DEBUG_KMS("Mode for pipe %c:\n", pipe == 0 ? 'A' : 'B');
 	drm_mode_debug_printmodeline(mode);
 
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 40e99bf..de21a82 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -224,6 +224,7 @@ extern u32 intel_panel_get_max_backlight(struct drm_device *dev);
 extern u32 intel_panel_get_backlight(struct drm_device *dev);
 extern void intel_panel_set_backlight(struct drm_device *dev, u32 level);
 
+extern int intel_panel_fitter_pipe (struct drm_device *dev);
 extern void intel_crtc_load_lut(struct drm_crtc *crtc);
 extern void intel_encoder_prepare (struct drm_encoder *encoder);
 extern void intel_encoder_commit (struct drm_encoder *encoder);
diff --git a/drivers/gpu/drm/i915/intel_overlay.c b/drivers/gpu/drm/i915/intel_overlay.c
index 375316a..da65d95 100644
--- a/drivers/gpu/drm/i915/intel_overlay.c
+++ b/drivers/gpu/drm/i915/intel_overlay.c
@@ -1053,7 +1053,7 @@ static int check_overlay_src(struct drm_device *dev,
  * Return the pipe currently connected to the panel fitter,
  * or -1 if the panel fitter is not present or not in use
  */
-static int intel_panel_fitter_pipe(struct drm_device *dev)
+int intel_panel_fitter_pipe(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	u32  pfit_control;