drm/i915: don't check inconsistent modeset state when force-restoring

It will be only consistent once we've restored all the crtcs. Since a
bunch of other callers also want to just restore a single crtc, add a
boolean to disable checking only where it doesn't make sense.

Note that intel_modeset_setup_hw_state already has a call to
intel_modeset_check_state at the end, so we don't reduce the amount of
checking.

v2: Try harder not to create a big patch (Chris).

v3: Even smaller (still Chris). Also fix a trailing space.

References: https://lkml.org/lkml/2013/3/16/60
Cc: Tomas Melin <tomas.melin@iki.fi>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@vger.kernel.org
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Tested-by: Tomas Melin <tomas.melin@iki.fi>
Tested-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -7916,7 +7916,7 @@ intel_modeset_check_state(struct drm_device *dev)
 	}
 }
 
-int intel_set_mode(struct drm_crtc *crtc,
+static int __intel_set_mode(struct drm_crtc *crtc,
 			    struct drm_display_mode *mode,
 			    int x, int y, struct drm_framebuffer *fb)
 {
@@ -8012,8 +8012,6 @@ int intel_set_mode(struct drm_crtc *crtc,
 	if (ret && crtc->enabled) {
 		crtc->hwmode = *saved_hwmode;
 		crtc->mode = *saved_mode;
-	} else {
-		intel_modeset_check_state(dev);
 	}
 
 out:
@@ -8022,6 +8020,20 @@ int intel_set_mode(struct drm_crtc *crtc,
 	return ret;
 }
 
+int intel_set_mode(struct drm_crtc *crtc,
+		     struct drm_display_mode *mode,
+		     int x, int y, struct drm_framebuffer *fb)
+{
+	int ret;
+
+	ret = __intel_set_mode(crtc, mode, x, y, fb);
+
+	if (ret == 0)
+		intel_modeset_check_state(crtc->dev);
+
+	return ret;
+}
+
 void intel_crtc_restore_mode(struct drm_crtc *crtc)
 {
 	intel_set_mode(crtc, &crtc->mode, crtc->x, crtc->y, crtc->fb);
@@ -9333,10 +9345,16 @@ void intel_modeset_setup_hw_state(struct drm_device *dev,
 	}
 
 	if (force_restore) {
+		/*
+		 * We need to use raw interfaces for restoring state to avoid
+		 * checking (bogus) intermediate states.
+		 */
 		for_each_pipe(pipe) {
 			struct drm_crtc *crtc =
 				dev_priv->pipe_to_crtc_mapping[pipe];
-			intel_crtc_restore_mode(crtc);
+
+			__intel_set_mode(crtc, &crtc->mode, crtc->x, crtc->y,
+					 crtc->fb);
 		}
 		list_for_each_entry(plane, &dev->mode_config.plane_list, head)
 			intel_plane_restore(plane);