drm: Add valid clones check

Check that all encoders attached to a given CRTC are valid
possible_clones of each other.

Signed-off-by: Jessica Zhang <[e-mail]>
Reviewed-by: Maxime Ripard <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]
Signed-off-by: Dmitry Baryshkov <[e-mail]>

drivers/gpu/drm/drm_atomic_helper.c

···
 	return 0;
 }
 
+static int drm_atomic_check_valid_clones(struct drm_atomic_state *state,
+					 struct drm_crtc *crtc)
+{
+	struct drm_encoder *drm_enc;
+	struct drm_crtc_state *crtc_state = drm_atomic_get_new_crtc_state(state,
+									  crtc);
+
+	drm_for_each_encoder_mask(drm_enc, crtc->dev, crtc_state->encoder_mask) {
+		if (!drm_enc->possible_clones) {
+			DRM_DEBUG("enc%d possible_clones is 0\n", drm_enc->base.id);
+			continue;
+		}
+
+		if ((crtc_state->encoder_mask & drm_enc->possible_clones) !=
+		    crtc_state->encoder_mask) {
+			DRM_DEBUG("crtc%d failed valid clone check for mask 0x%x\n",
+				  crtc->base.id, crtc_state->encoder_mask);
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
 /**
  * drm_atomic_helper_check_modeset - validate state object for modeset changes
  * @dev: DRM device
···
 			return ret;
 
 		ret = drm_atomic_add_affected_planes(state, crtc);
+		if (ret != 0)
+			return ret;
+
+		ret = drm_atomic_check_valid_clones(state, crtc);
 		if (ret != 0)
 			return ret;
 	}