drm/fb-helper: Push down modeset lock into FB helpers

Move the modeset locking from drivers into FB helpers.

v2: Also handle intel_connector_add_to_fbdev.

v3: Prevent race in intel_dp_mst with ->detect (Maarten)

Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Tested-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Thierry Reding <treding@nvidia.com> (v1)
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170704151833.17304-2-daniel.vetter@ffwll.ch

drivers/gpu/drm/drm_fb_helper.c

@@ -109,8 +109,8 @@ static DEFINE_MUTEX(kernel_fb_helper_lock);
 	for (({ lockdep_assert_held(&(fbh)->dev->mode_config.mutex); }), \
 	     i__ = 0; i__ < (fbh)->connector_count; i__++)
 
-int drm_fb_helper_add_one_connector(struct drm_fb_helper *fb_helper,
-				    struct drm_connector *connector)
+static int __drm_fb_helper_add_one_connector(struct drm_fb_helper *fb_helper,
+					     struct drm_connector *connector)
 {
 	struct drm_fb_helper_connector *fb_conn;
 	struct drm_fb_helper_connector **temp;
@@ -141,8 +141,23 @@ int drm_fb_helper_add_one_connector(struct drm_fb_helper *fb_helper,
 	drm_connector_get(connector);
 	fb_conn->connector = connector;
 	fb_helper->connector_info[fb_helper->connector_count++] = fb_conn;
+
 	return 0;
 }
+
+int drm_fb_helper_add_one_connector(struct drm_fb_helper *fb_helper,
+				    struct drm_connector *connector)
+{
+	int err;
+
+	mutex_lock(&fb_helper->dev->mode_config.mutex);
+
+	err = __drm_fb_helper_add_one_connector(fb_helper, connector);
+
+	mutex_unlock(&fb_helper->dev->mode_config.mutex);
+
+	return err;
+}
 EXPORT_SYMBOL(drm_fb_helper_add_one_connector);
 
 /**
@@ -172,8 +187,7 @@ int drm_fb_helper_single_add_all_connectors(struct drm_fb_helper *fb_helper)
 	mutex_lock(&dev->mode_config.mutex);
 	drm_connector_list_iter_begin(dev, &conn_iter);
 	drm_for_each_connector_iter(connector, &conn_iter) {
-		ret = drm_fb_helper_add_one_connector(fb_helper, connector);
-
+		ret = __drm_fb_helper_add_one_connector(fb_helper, connector);
 		if (ret)
 			goto fail;
 	}
@@ -198,8 +212,8 @@ out:
 }
 EXPORT_SYMBOL(drm_fb_helper_single_add_all_connectors);
 
-int drm_fb_helper_remove_one_connector(struct drm_fb_helper *fb_helper,
-				       struct drm_connector *connector)
+static int __drm_fb_helper_remove_one_connector(struct drm_fb_helper *fb_helper,
+						struct drm_connector *connector)
 {
 	struct drm_fb_helper_connector *fb_helper_connector;
 	int i, j;
@@ -227,6 +241,20 @@ int drm_fb_helper_remove_one_connector(struct drm_fb_helper *fb_helper,
 
 	return 0;
 }
+
+int drm_fb_helper_remove_one_connector(struct drm_fb_helper *fb_helper,
+				       struct drm_connector *connector)
+{
+	int err;
+
+	mutex_lock(&fb_helper->dev->mode_config.mutex);
+
+	err = __drm_fb_helper_remove_one_connector(fb_helper, connector);
+
+	mutex_unlock(&fb_helper->dev->mode_config.mutex);
+
+	return err;
+}
 EXPORT_SYMBOL(drm_fb_helper_remove_one_connector);
 
 static void drm_fb_helper_save_lut_atomic(struct drm_crtc *crtc, struct drm_fb_helper *helper)

drivers/gpu/drm/i915/intel_dp_mst.c

@@ -501,11 +501,8 @@ static struct drm_connector *intel_dp_add_mst_connector(struct drm_dp_mst_topolo
 static void intel_dp_register_mst_connector(struct drm_connector *connector)
 {
 	struct intel_connector *intel_connector = to_intel_connector(connector);
-	struct drm_device *dev = connector->dev;
 
-	drm_modeset_lock_all(dev);
 	intel_connector_add_to_fbdev(intel_connector);
-	drm_modeset_unlock_all(dev);
 
 	drm_connector_register(&intel_connector->base);
 }
@@ -514,15 +511,15 @@ static void intel_dp_destroy_mst_connector(struct drm_dp_mst_topology_mgr *mgr,
 					   struct drm_connector *connector)
 {
 	struct intel_connector *intel_connector = to_intel_connector(connector);
-	struct drm_device *dev = connector->dev;
 
 	drm_connector_unregister(connector);
 
 	/* need to nuke the connector */
-	drm_modeset_lock_all(dev);
 	intel_connector_remove_from_fbdev(intel_connector);
+	/* prevent race with the check in ->detect */
+	drm_modeset_lock(&connector->dev->mode_config.connection_mutex, NULL);
 	intel_connector->mst_port = NULL;
-	drm_modeset_unlock_all(dev);
+	drm_modeset_unlock(&connector->dev->mode_config.connection_mutex);
 
 	drm_connector_unreference(&intel_connector->base);
 	DRM_DEBUG_KMS("\n");

drivers/gpu/drm/radeon/radeon_dp_mst.c

@@ -300,9 +300,7 @@ static void radeon_dp_register_mst_connector(struct drm_connector *connector)
 	struct drm_device *dev = connector->dev;
 	struct radeon_device *rdev = dev->dev_private;
 
-	drm_modeset_lock_all(dev);
 	radeon_fb_add_connector(rdev, connector);
-	drm_modeset_unlock_all(dev);
 
 	drm_connector_register(connector);
 }
@@ -315,13 +313,8 @@ static void radeon_dp_destroy_mst_connector(struct drm_dp_mst_topology_mgr *mgr,
 	struct radeon_device *rdev = dev->dev_private;
 
 	drm_connector_unregister(connector);
-	/* need to nuke the connector */
-	drm_modeset_lock_all(dev);
-	/* dpms off */
 	radeon_fb_remove_connector(rdev, connector);
-
 	drm_connector_cleanup(connector);
-	drm_modeset_unlock_all(dev);
 
 	kfree(connector);
 	DRM_DEBUG_KMS("\n");