drm/i915: Set crtc->new_config to NULL for pipes that are about to be disabled

crtc->new_config is only relevant for pipes that are going to be active
post-modeset. Set the pointer to NULL for all pipes that are going to
be disabled. This is done to help catch bugs where some piece of code
would go looking at crtc->new_config even if the data there is stale.

v2: Clear new_config in disable_crtc_nofb() too (Imre)

Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -8787,6 +8787,11 @@ static void intel_modeset_update_staged_output_state(struct drm_device *dev)
 	list_for_each_entry(crtc, &dev->mode_config.crtc_list,
 			    base.head) {
 		crtc->new_enabled = crtc->base.enabled;
+
+		if (crtc->new_enabled)
+			crtc->new_config = &crtc->config;
+		else
+			crtc->new_config = NULL;
 	}
 }
 
@@ -9219,7 +9224,9 @@ intel_modeset_update_state(struct drm_device *dev, unsigned prepare_pipes)
 	list_for_each_entry(intel_crtc, &dev->mode_config.crtc_list,
 			    base.head) {
 		WARN_ON(intel_crtc->base.enabled != intel_crtc_in_use(&intel_crtc->base));
-		WARN_ON(intel_crtc->new_config != &intel_crtc->config);
+		WARN_ON(intel_crtc->new_config &&
+			intel_crtc->new_config != &intel_crtc->config);
+		WARN_ON(intel_crtc->base.enabled != !!intel_crtc->new_config);
 	}
 
 	list_for_each_entry(connector, &dev->mode_config.connector_list, head) {
@@ -9818,6 +9825,11 @@ static void intel_set_config_restore_state(struct drm_device *dev,
 	count = 0;
 	list_for_each_entry(crtc, &dev->mode_config.crtc_list, base.head) {
 		crtc->new_enabled = config->save_crtc_enabled[count++];
+
+		if (crtc->new_enabled)
+			crtc->new_config = &crtc->config;
+		else
+			crtc->new_config = NULL;
 	}
 
 	count = 0;
@@ -10019,6 +10031,11 @@ intel_modeset_stage_output_state(struct drm_device *dev,
 				      crtc->new_enabled ? "en" : "dis");
 			config->mode_changed = true;
 		}
+
+		if (crtc->new_enabled)
+			crtc->new_config = &crtc->config;
+		else
+			crtc->new_config = NULL;
 	}
 
 	return 0;
@@ -10045,6 +10062,7 @@ static void disable_crtc_nofb(struct intel_crtc *crtc)
 	}
 
 	crtc->new_enabled = false;
+	crtc->new_config = NULL;
 }
 
 static int intel_crtc_set_config(struct drm_mode_set *set)
@@ -10289,8 +10307,6 @@ static void intel_crtc_init(struct drm_device *dev, int pipe)
 	dev_priv->plane_to_crtc_mapping[intel_crtc->plane] = &intel_crtc->base;
 	dev_priv->pipe_to_crtc_mapping[intel_crtc->pipe] = &intel_crtc->base;
 
-	intel_crtc->new_config = &intel_crtc->config;
-
 	drm_crtc_helper_add(&intel_crtc->base, &intel_helper_funcs);
 }