diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 23739609427d..e6862a744210 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -420,18 +420,21 @@ drm_atomic_replace_property_blob_from_id(struct drm_crtc *crtc,
 					 ssize_t expected_size,
 					 bool *replaced)
 {
-	struct drm_device *dev = crtc->dev;
 	struct drm_property_blob *new_blob = NULL;
 
 	if (blob_id != 0) {
-		new_blob = drm_property_lookup_blob(dev, blob_id);
+		new_blob = drm_property_lookup_blob(crtc->dev, blob_id);
 		if (new_blob == NULL)
 			return -EINVAL;
-		if (expected_size > 0 && expected_size != new_blob->length)
+
+		if (expected_size > 0 && expected_size != new_blob->length) {
+			drm_property_unreference_blob(new_blob);
 			return -EINVAL;
+		}
 	}
 
 	drm_atomic_replace_property_blob(blob, new_blob, replaced);
+	drm_property_unreference_blob(new_blob);
 
 	return 0;
 }
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index c3f83476f996..21f992605541 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -594,10 +594,6 @@ drm_atomic_helper_check_planes(struct drm_device *dev,
 	struct drm_plane_state *plane_state;
 	int i, ret = 0;
 
-	ret = drm_atomic_normalize_zpos(dev, state);
-	if (ret)
-		return ret;
-
 	for_each_plane_in_state(state, plane, plane_state, i) {
 		const struct drm_plane_helper_funcs *funcs;
 
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 04e457117980..aa644487749c 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -914,6 +914,7 @@ static void drm_dp_destroy_port(struct kref *kref)
 		/* no need to clean up vcpi
 		 * as if we have no connector we never setup a vcpi */
 		drm_dp_port_teardown_pdt(port, port->pdt);
+		port->pdt = DP_PEER_DEVICE_NONE;
 	}
 	kfree(port);
 }
@@ -1159,7 +1160,9 @@ static void drm_dp_add_port(struct drm_dp_mst_branch *mstb,
 			drm_dp_put_port(port);
 			goto out;
 		}
-		if (port->port_num >= DP_MST_LOGICAL_PORT_0) {
+		if ((port->pdt == DP_PEER_DEVICE_DP_LEGACY_CONV ||
+		     port->pdt == DP_PEER_DEVICE_SST_SINK) &&
+		    port->port_num >= DP_MST_LOGICAL_PORT_0) {
 			port->cached_edid = drm_get_edid(port->connector, &port->aux.ddc);
 			drm_mode_connector_set_tile_property(port->connector);
 		}
@@ -2919,6 +2922,7 @@ static void drm_dp_destroy_connector_work(struct work_struct *work)
 		mgr->cbs->destroy_connector(mgr, port->connector);
 
 		drm_dp_port_teardown_pdt(port, port->pdt);
+		port->pdt = DP_PEER_DEVICE_NONE;
 
 		if (!port->input && port->vcpi.vcpi > 0) {
 			drm_dp_mst_reset_vcpi_slots(mgr, port);
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 03414bde1f15..6c75e62c0b22 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -131,7 +131,12 @@ int drm_fb_helper_single_add_all_connectors(struct drm_fb_helper *fb_helper)
 	return 0;
 fail:
 	for (i = 0; i < fb_helper->connector_count; i++) {
-		kfree(fb_helper->connector_info[i]);
+		struct drm_fb_helper_connector *fb_helper_connector =
+			fb_helper->connector_info[i];
+
+		drm_connector_unreference(fb_helper_connector->connector);
+
+		kfree(fb_helper_connector);
 		fb_helper->connector_info[i] = NULL;
 	}
 	fb_helper->connector_count = 0;
@@ -603,6 +608,24 @@ int drm_fb_helper_blank(int blank, struct fb_info *info)
 }
 EXPORT_SYMBOL(drm_fb_helper_blank);
 
+static void drm_fb_helper_modeset_release(struct drm_fb_helper *helper,
+					  struct drm_mode_set *modeset)
+{
+	int i;
+
+	for (i = 0; i < modeset->num_connectors; i++) {
+		drm_connector_unreference(modeset->connectors[i]);
+		modeset->connectors[i] = NULL;
+	}
+	modeset->num_connectors = 0;
+
+	drm_mode_destroy(helper->dev, modeset->mode);
+	modeset->mode = NULL;
+
+	/* FIXME should hold a ref? */
+	modeset->fb = NULL;
+}
+
 static void drm_fb_helper_crtc_free(struct drm_fb_helper *helper)
 {
 	int i;
@@ -612,10 +635,12 @@ static void drm_fb_helper_crtc_free(struct drm_fb_helper *helper)
 		kfree(helper->connector_info[i]);
 	}
 	kfree(helper->connector_info);
+
 	for (i = 0; i < helper->crtc_count; i++) {
-		kfree(helper->crtc_info[i].mode_set.connectors);
-		if (helper->crtc_info[i].mode_set.mode)
-			drm_mode_destroy(helper->dev, helper->crtc_info[i].mode_set.mode);
+		struct drm_mode_set *modeset = &helper->crtc_info[i].mode_set;
+
+		drm_fb_helper_modeset_release(helper, modeset);
+		kfree(modeset->connectors);
 	}
 	kfree(helper->crtc_info);
 }
@@ -644,7 +669,9 @@ static void drm_fb_helper_dirty_work(struct work_struct *work)
 	clip->x2 = clip->y2 = 0;
 	spin_unlock_irqrestore(&helper->dirty_lock, flags);
 
-	helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, &clip_copy, 1);
+	/* call dirty callback only when it has been really touched */
+	if (clip_copy.x1 < clip_copy.x2 && clip_copy.y1 < clip_copy.y2)
+		helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, &clip_copy, 1);
 }
 
 /**
@@ -2088,7 +2115,6 @@ static void drm_setup_crtcs(struct drm_fb_helper *fb_helper)
 	struct drm_fb_helper_crtc **crtcs;
 	struct drm_display_mode **modes;
 	struct drm_fb_offset *offsets;
-	struct drm_mode_set *modeset;
 	bool *enabled;
 	int width, height;
 	int i;
@@ -2136,45 +2162,35 @@ static void drm_setup_crtcs(struct drm_fb_helper *fb_helper)
 
 	/* need to set the modesets up here for use later */
 	/* fill out the connector<->crtc mappings into the modesets */
-	for (i = 0; i < fb_helper->crtc_count; i++) {
-		modeset = &fb_helper->crtc_info[i].mode_set;
-		modeset->num_connectors = 0;
-		modeset->fb = NULL;
-	}
+	for (i = 0; i < fb_helper->crtc_count; i++)
+		drm_fb_helper_modeset_release(fb_helper,
+					      &fb_helper->crtc_info[i].mode_set);
 
 	for (i = 0; i < fb_helper->connector_count; i++) {
 		struct drm_display_mode *mode = modes[i];
 		struct drm_fb_helper_crtc *fb_crtc = crtcs[i];
 		struct drm_fb_offset *offset = &offsets[i];
-		modeset = &fb_crtc->mode_set;
+		struct drm_mode_set *modeset = &fb_crtc->mode_set;
 
 		if (mode && fb_crtc) {
+			struct drm_connector *connector =
+				fb_helper->connector_info[i]->connector;
+
 			DRM_DEBUG_KMS("desired mode %s set on crtc %d (%d,%d)\n",
 				      mode->name, fb_crtc->mode_set.crtc->base.id, offset->x, offset->y);
+
 			fb_crtc->desired_mode = mode;
 			fb_crtc->x = offset->x;
 			fb_crtc->y = offset->y;
-			if (modeset->mode)
-				drm_mode_destroy(dev, modeset->mode);
 			modeset->mode = drm_mode_duplicate(dev,
 							   fb_crtc->desired_mode);
-			modeset->connectors[modeset->num_connectors++] = fb_helper->connector_info[i]->connector;
+			drm_connector_reference(connector);
+			modeset->connectors[modeset->num_connectors++] = connector;
 			modeset->fb = fb_helper->fb;
 			modeset->x = offset->x;
 			modeset->y = offset->y;
 		}
 	}
-
-	/* Clear out any old modes if there are no more connected outputs. */
-	for (i = 0; i < fb_helper->crtc_count; i++) {
-		modeset = &fb_helper->crtc_info[i].mode_set;
-		if (modeset->num_connectors == 0) {
-			BUG_ON(modeset->fb);
-			if (modeset->mode)
-				drm_mode_destroy(dev, modeset->mode);
-			modeset->mode = NULL;
-		}
-	}
 out:
 	kfree(crtcs);
 	kfree(modes);
diff --git a/drivers/gpu/drm/exynos/exynos_drm_drv.c b/drivers/gpu/drm/exynos/exynos_drm_drv.c
index def78c8c1780..f86e7c846678 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_drv.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_drv.c
@@ -262,6 +262,26 @@ int exynos_atomic_commit(struct drm_device *dev, struct drm_atomic_state *state,
 	return 0;
 }
 
+int exynos_atomic_check(struct drm_device *dev,
+			struct drm_atomic_state *state)
+{
+	int ret;
+
+	ret = drm_atomic_helper_check_modeset(dev, state);
+	if (ret)
+		return ret;
+
+	ret = drm_atomic_normalize_zpos(dev, state);
+	if (ret)
+		return ret;
+
+	ret = drm_atomic_helper_check_planes(dev, state);
+	if (ret)
+		return ret;
+
+	return ret;
+}
+
 static int exynos_drm_open(struct drm_device *dev, struct drm_file *file)
 {
 	struct drm_exynos_file_private *file_priv;
diff --git a/drivers/gpu/drm/exynos/exynos_drm_drv.h b/drivers/gpu/drm/exynos/exynos_drm_drv.h
index d215149e737b..80c4d5b81689 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_drv.h
+++ b/drivers/gpu/drm/exynos/exynos_drm_drv.h
@@ -301,6 +301,7 @@ static inline int exynos_dpi_bind(struct drm_device *dev,
 
 int exynos_atomic_commit(struct drm_device *dev, struct drm_atomic_state *state,
 			 bool nonblock);
+int exynos_atomic_check(struct drm_device *dev, struct drm_atomic_state *state);
 
 
 extern struct platform_driver fimd_driver;
diff --git a/drivers/gpu/drm/exynos/exynos_drm_fb.c b/drivers/gpu/drm/exynos/exynos_drm_fb.c
index 40ce841eb952..23cce0a3f5fc 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_fb.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_fb.c
@@ -190,7 +190,7 @@ dma_addr_t exynos_drm_fb_dma_addr(struct drm_framebuffer *fb, int index)
 static const struct drm_mode_config_funcs exynos_drm_mode_config_funcs = {
 	.fb_create = exynos_user_fb_create,
 	.output_poll_changed = exynos_drm_output_poll_changed,
-	.atomic_check = drm_atomic_helper_check,
+	.atomic_check = exynos_atomic_check,
 	.atomic_commit = exynos_atomic_commit,
 };
 
diff --git a/drivers/gpu/drm/rcar-du/rcar_du_kms.c b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
index bd9c3bb9252c..392c7e6de042 100644
--- a/drivers/gpu/drm/rcar-du/rcar_du_kms.c
+++ b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
@@ -231,8 +231,16 @@ static int rcar_du_atomic_check(struct drm_device *dev,
 	struct rcar_du_device *rcdu = dev->dev_private;
 	int ret;
 
-	ret = drm_atomic_helper_check(dev, state);
-	if (ret < 0)
+	ret = drm_atomic_helper_check_modeset(dev, state);
+	if (ret)
+		return ret;
+
+	ret = drm_atomic_normalize_zpos(dev, state);
+	if (ret)
+		return ret;
+
+	ret = drm_atomic_helper_check_planes(dev, state);
+	if (ret)
 		return ret;
 
 	if (rcar_du_has(rcdu, RCAR_DU_FEATURE_VSP1_SOURCE))
diff --git a/drivers/gpu/drm/sti/sti_drv.c b/drivers/gpu/drm/sti/sti_drv.c
index 2784919a7366..9df308565f6c 100644
--- a/drivers/gpu/drm/sti/sti_drv.c
+++ b/drivers/gpu/drm/sti/sti_drv.c
@@ -195,6 +195,26 @@ static void sti_atomic_work(struct work_struct *work)
 	sti_atomic_complete(private, private->commit.state);
 }
 
+static int sti_atomic_check(struct drm_device *dev,
+			    struct drm_atomic_state *state)
+{
+	int ret;
+
+	ret = drm_atomic_helper_check_modeset(dev, state);
+	if (ret)
+		return ret;
+
+	ret = drm_atomic_normalize_zpos(dev, state);
+	if (ret)
+		return ret;
+
+	ret = drm_atomic_helper_check_planes(dev, state);
+	if (ret)
+		return ret;
+
+	return ret;
+}
+
 static int sti_atomic_commit(struct drm_device *drm,
 			     struct drm_atomic_state *state, bool nonblock)
 {
@@ -248,7 +268,7 @@ static void sti_output_poll_changed(struct drm_device *ddev)
 static const struct drm_mode_config_funcs sti_mode_config_funcs = {
 	.fb_create = drm_fb_cma_create,
 	.output_poll_changed = sti_output_poll_changed,
-	.atomic_check = drm_atomic_helper_check,
+	.atomic_check = sti_atomic_check,
 	.atomic_commit = sti_atomic_commit,
 };
 
diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
index 43cf193e54d6..8b4dc62470ff 100644
--- a/include/drm/drm_plane.h
+++ b/include/drm/drm_plane.h
@@ -47,8 +47,14 @@ struct drm_crtc;
  * @src_h: height of visible portion of plane (in 16.16)
  * @rotation: rotation of the plane
  * @zpos: priority of the given plane on crtc (optional)
+ *	Note that multiple active planes on the same crtc can have an identical
+ *	zpos value. The rule to solving the conflict is to compare the plane
+ *	object IDs; the plane with a higher ID must be stacked on top of a
+ *	plane with a lower ID.
  * @normalized_zpos: normalized value of zpos: unique, range from 0 to N-1
- *	where N is the number of active planes for given crtc
+ *	where N is the number of active planes for given crtc. Note that
+ *	the driver must call drm_atomic_normalize_zpos() to update this before
+ *	it can be trusted.
  * @src: clipped source coordinates of the plane (in 16.16)
  * @dst: clipped destination coordinates of the plane
  * @visible: visibility of the plane