drm/i915: Clear pfit registers when not used by any outputs

... otherwise the panel-fitter may be left enabled with random settings
and cause unintended filtering (i.e. blurring of native modes on external
panels).

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=31942
Reported-and-tested-by: Ben Kohler <bkohler@gmail.com>
Tested-by: Ciprian Docan <docan@eden.rutgers.edu>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

3 files changed, 17 insertions, 11 deletions

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index bee24b1a58e8..255b52ee0091 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -5336,9 +5336,14 @@ static void intel_setup_outputs(struct drm_device *dev)
         struct drm_i915_private *dev_priv = dev->dev_private;
         struct intel_encoder *encoder;
         bool dpd_is_edp = false;
+        bool has_lvds = false;
 
         if (IS_MOBILE(dev) && !IS_I830(dev))
-                intel_lvds_init(dev);
+                has_lvds = intel_lvds_init(dev);
+        if (!has_lvds && !HAS_PCH_SPLIT(dev)) {
+                /* disable the panel fitter on everything but LVDS */
+                I915_WRITE(PFIT_CONTROL, 0);
+        }
 
         if (HAS_PCH_SPLIT(dev)) {
                 dpd_is_edp = intel_dpd_is_edp(dev);
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 21551fe74541..e52c6125bb1f 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -237,7 +237,7 @@ extern bool intel_sdvo_init(struct drm_device *dev, int output_device);
 extern void intel_dvo_init(struct drm_device *dev);
 extern void intel_tv_init(struct drm_device *dev);
 extern void intel_mark_busy(struct drm_device *dev, struct drm_gem_object *obj);
-extern void intel_lvds_init(struct drm_device *dev);
+extern bool intel_lvds_init(struct drm_device *dev);
 extern void intel_dp_init(struct drm_device *dev, int dp_reg);
 void
 intel_dp_set_m_n(struct drm_crtc *crtc, struct drm_display_mode *mode,
diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c
index 4324a326f98e..f79327fc6653 100644
--- a/drivers/gpu/drm/i915/intel_lvds.c
+++ b/drivers/gpu/drm/i915/intel_lvds.c
@@ -837,7 +837,7 @@ static bool intel_lvds_ddc_probe(struct drm_device *dev, u8 pin)
  * Create the connector, register the LVDS DDC bus, and try to figure out what
  * modes we can display on the LVDS panel (if present).
  */
-void intel_lvds_init(struct drm_device *dev)
+bool intel_lvds_init(struct drm_device *dev)
 {
         struct drm_i915_private *dev_priv = dev->dev_private;
         struct intel_lvds *intel_lvds;
@@ -853,37 +853,37 @@ void intel_lvds_init(struct drm_device *dev)
 
         /* Skip init on machines we know falsely report LVDS */
         if (dmi_check_system(intel_no_lvds))
-                return;
+                return false;
 
         pin = GMBUS_PORT_PANEL;
         if (!lvds_is_present_in_vbt(dev, &pin)) {
                 DRM_DEBUG_KMS("LVDS is not present in VBT\n");
-                return;
+                return false;
         }
 
         if (HAS_PCH_SPLIT(dev)) {
                 if ((I915_READ(PCH_LVDS) & LVDS_DETECTED) == 0)
-                        return;
+                        return false;
                 if (dev_priv->edp.support) {
                         DRM_DEBUG_KMS("disable LVDS for eDP support\n");
-                        return;
+                        return false;
                 }
         }
 
         if (!intel_lvds_ddc_probe(dev, pin)) {
                 DRM_DEBUG_KMS("LVDS did not respond to DDC probe\n");
-                return;
+                return false;
         }
 
         intel_lvds = kzalloc(sizeof(struct intel_lvds), GFP_KERNEL);
         if (!intel_lvds) {
-                return;
+                return false;
         }
 
         intel_connector = kzalloc(sizeof(struct intel_connector), GFP_KERNEL);
         if (!intel_connector) {
                 kfree(intel_lvds);
-                return;
+                return false;
         }
 
         if (!HAS_PCH_SPLIT(dev)) {
@@ -1026,7 +1026,7 @@ out:
         /* keep the LVDS connector */
         dev_priv->int_lvds_connector = connector;
         drm_sysfs_connector_add(connector);
-        return;
+        return true;
 
 failed:
         DRM_DEBUG_KMS("No LVDS modes found, disabling.\n");
@@ -1034,4 +1034,5 @@ failed:
         drm_encoder_cleanup(encoder);
         kfree(intel_lvds);
         kfree(intel_connector);
+        return false;
 }