--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -1702,27 +1702,6 @@ drm_atomic_set_crtc_for_connector(struct
 	struct drm_connector *connector = conn_state->connector;
 	struct drm_crtc_state *crtc_state;
 
-	/*
-	 * For compatibility with legacy users, we want to make sure that
-	 * we allow DPMS On<->Off modesets on unregistered connectors, since
-	 * legacy modesetting users will not be expecting these to fail. We do
-	 * not however, want to allow legacy users to assign a connector
-	 * that's been unregistered from sysfs to another CRTC, since doing
-	 * this with a now non-existent connector could potentially leave us
-	 * in an invalid state.
-	 *
-	 * Since the connector can be unregistered at any point during an
-	 * atomic check or commit, this is racy. But that's OK: all we care
-	 * about is ensuring that userspace can't use this connector for new
-	 * configurations after it's been notified that the connector is no
-	 * longer present.
-	 */
-	if (!READ_ONCE(connector->registered) && crtc) {
-		DRM_DEBUG_ATOMIC("[CONNECTOR:%d:%s] is not registered\n",
-				 connector->base.id, connector->name);
-		return -EINVAL;
-	}
-
 	if (conn_state->crtc == crtc)
 		return 0;
 
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -307,6 +307,26 @@ update_connector_routing(struct drm_atom
 		return 0;
 	}
 
+	crtc_state = drm_atomic_get_new_crtc_state(state,
+						   new_connector_state->crtc);
+	/*
+	 * For compatibility with legacy users, we want to make sure that
+	 * we allow DPMS On->Off modesets on unregistered connectors. Modesets
+	 * which would result in anything else must be considered invalid, to
+	 * avoid turning on new displays on dead connectors.
+	 *
+	 * Since the connector can be unregistered at any point during an
+	 * atomic check or commit, this is racy. But that's OK: all we care
+	 * about is ensuring that userspace can't do anything but shut off the
+	 * display on a connector that was destroyed after its been notified,
+	 * not before.
+	 */
+	if (drm_connector_is_unregistered(connector) && crtc_state->active) {
+		DRM_DEBUG_ATOMIC("[CONNECTOR:%d:%s] is not registered\n",
+				 connector->base.id, connector->name);
+		return -EINVAL;
+	}
+
 	funcs = connector->helper_private;
 
 	if (funcs->atomic_best_encoder)
@@ -351,7 +371,6 @@ update_connector_routing(struct drm_atom
 
 	set_best_encoder(state, new_connector_state, new_encoder);
 
-	crtc_state = drm_atomic_get_new_crtc_state(state, new_connector_state->crtc);
 	crtc_state->connectors_changed = true;
 
 	DRM_DEBUG_ATOMIC("[CONNECTOR:%d:%s] using [ENCODER:%d:%s] on [CRTC:%d:%s]\n",
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -375,7 +375,8 @@ void drm_connector_cleanup(struct drm_co
 	/* The connector should have been removed from userspace long before
 	 * it is finally destroyed.
 	 */
-	if (WARN_ON(connector->registered))
+	if (WARN_ON(connector->registration_state ==
+		    DRM_CONNECTOR_REGISTERED))
 		drm_connector_unregister(connector);
 
 	if (connector->tile_group) {
@@ -432,7 +433,7 @@ int drm_connector_register(struct drm_co
 		return 0;
 
 	mutex_lock(&connector->mutex);
-	if (connector->registered)
+	if (connector->registration_state != DRM_CONNECTOR_INITIALIZING)
 		goto unlock;
 
 	ret = drm_sysfs_connector_add(connector);
@@ -452,7 +453,7 @@ int drm_connector_register(struct drm_co
 
 	drm_mode_object_register(connector->dev, &connector->base);
 
-	connector->registered = true;
+	connector->registration_state = DRM_CONNECTOR_REGISTERED;
 	goto unlock;
 
 err_debugfs:
@@ -474,7 +475,7 @@ EXPORT_SYMBOL(drm_connector_register);
 void drm_connector_unregister(struct drm_connector *connector)
 {
 	mutex_lock(&connector->mutex);
-	if (!connector->registered) {
+	if (connector->registration_state != DRM_CONNECTOR_REGISTERED) {
 		mutex_unlock(&connector->mutex);
 		return;
 	}
@@ -485,7 +486,7 @@ void drm_connector_unregister(struct drm
 	drm_sysfs_connector_remove(connector);
 	drm_debugfs_connector_remove(connector);
 
-	connector->registered = false;
+	connector->registration_state = DRM_CONNECTOR_UNREGISTERED;
 	mutex_unlock(&connector->mutex);
 }
 EXPORT_SYMBOL(drm_connector_unregister);
--- a/drivers/gpu/drm/i915/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/intel_dp_mst.c
@@ -77,7 +77,7 @@ static bool intel_dp_mst_compute_config(
 	pipe_config->pbn = mst_pbn;
 
 	/* Zombie connectors can't have VCPI slots */
-	if (READ_ONCE(connector->registered)) {
+	if (!drm_connector_is_unregistered(connector)) {
 		slots = drm_dp_atomic_find_vcpi_slots(state,
 						      &intel_dp->mst_mgr,
 						      port,
@@ -317,7 +317,7 @@ static int intel_dp_mst_get_ddc_modes(st
 	struct edid *edid;
 	int ret;
 
-	if (!READ_ONCE(connector->registered))
+	if (drm_connector_is_unregistered(connector))
 		return intel_connector_update_modes(connector, NULL);
 
 	edid = drm_dp_mst_get_edid(connector, &intel_dp->mst_mgr, intel_connector->port);
@@ -333,7 +333,7 @@ intel_dp_mst_detect(struct drm_connector
 	struct intel_connector *intel_connector = to_intel_connector(connector);
 	struct intel_dp *intel_dp = intel_connector->mst_port;
 
-	if (!READ_ONCE(connector->registered))
+	if (drm_connector_is_unregistered(connector))
 		return connector_status_disconnected;
 	return drm_dp_mst_detect_port(connector, &intel_dp->mst_mgr,
 				      intel_connector->port);
@@ -376,7 +376,7 @@ intel_dp_mst_mode_valid(struct drm_conne
 	int bpp = 24; /* MST uses fixed bpp */
 	int max_rate, mode_rate, max_lanes, max_link_clock;
 
-	if (!READ_ONCE(connector->registered))
+	if (drm_connector_is_unregistered(connector))
 		return MODE_ERROR;
 
 	if (mode->flags & DRM_MODE_FLAG_DBLSCAN)
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -81,6 +81,53 @@ enum drm_connector_status {
 	connector_status_unknown = 3,
 };
 
+/**
+ * enum drm_connector_registration_status - userspace registration status for
+ * a &drm_connector
+ *
+ * This enum is used to track the status of initializing a connector and
+ * registering it with userspace, so that DRM can prevent bogus modesets on
+ * connectors that no longer exist.
+ */
+enum drm_connector_registration_state {
+	/**
+	 * @DRM_CONNECTOR_INITIALIZING: The connector has just been created,
+	 * but has yet to be exposed to userspace. There should be no
+	 * additional restrictions to how the state of this connector may be
+	 * modified.
+	 */
+	DRM_CONNECTOR_INITIALIZING = 0,
+
+	/**
+	 * @DRM_CONNECTOR_REGISTERED: The connector has been fully initialized
+	 * and registered with sysfs, as such it has been exposed to
+	 * userspace. There should be no additional restrictions to how the
+	 * state of this connector may be modified.
+	 */
+	DRM_CONNECTOR_REGISTERED = 1,
+
+	/**
+	 * @DRM_CONNECTOR_UNREGISTERED: The connector has either been exposed
+	 * to userspace and has since been unregistered and removed from
+	 * userspace, or the connector was unregistered before it had a chance
+	 * to be exposed to userspace (e.g. still in the
+	 * @DRM_CONNECTOR_INITIALIZING state). When a connector is
+	 * unregistered, there are additional restrictions to how its state
+	 * may be modified:
+	 *
+	 * - An unregistered connector may only have its DPMS changed from
+	 *   On->Off. Once DPMS is changed to Off, it may not be switched back
+	 *   to On.
+	 * - Modesets are not allowed on unregistered connectors, unless they
+	 *   would result in disabling its assigned CRTCs. This means
+	 *   disabling a CRTC on an unregistered connector is OK, but enabling
+	 *   one is not.
+	 * - Removing a CRTC from an unregistered connector is OK, but new
+	 *   CRTCs may never be assigned to an unregistered connector.
+	 */
+	DRM_CONNECTOR_UNREGISTERED = 2,
+};
+
 enum subpixel_order {
 	SubPixelUnknown = 0,
 	SubPixelHorizontalRGB,
@@ -852,10 +899,12 @@ struct drm_connector {
 	bool ycbcr_420_allowed;
 
 	/**
-	 * @registered: Is this connector exposed (registered) with userspace?
+	 * @registration_state: Is this connector initializing, exposed
+	 * (registered) with userspace, or unregistered?
+	 *
 	 * Protected by @mutex.
 	 */
-	bool registered;
+	enum drm_connector_registration_state registration_state;
 
 	/**
 	 * @modes:
@@ -1165,6 +1214,24 @@ static inline void drm_connector_unrefer
 	drm_connector_put(connector);
 }
 
+/**
+ * drm_connector_is_unregistered - has the connector been unregistered from
+ * userspace?
+ * @connector: DRM connector
+ *
+ * Checks whether or not @connector has been unregistered from userspace.
+ *
+ * Returns:
+ * True if the connector was unregistered, false if the connector is
+ * registered or has not yet been registered with userspace.
+ */
+static inline bool
+drm_connector_is_unregistered(struct drm_connector *connector)
+{
+	return READ_ONCE(connector->registration_state) ==
+		DRM_CONNECTOR_UNREGISTERED;
+}
+
 const char *drm_get_connector_status_name(enum drm_connector_status status);
 const char *drm_get_subpixel_order_name(enum subpixel_order order);
 const char *drm_get_dpms_name(int val);
