drm/atomic-helper: remove modeset_lock_all from helper_resume

Atomic code rely shouldn't rely on the magic hidden acquire context.

v2: Remove unused config local var (gcc).
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170403083304.9083-5-daniel.vetter@ffwll.ch

drivers/gpu/drm/drm_atomic_helper.c

@@ -2622,14 +2622,22 @@ EXPORT_SYMBOL(drm_atomic_helper_commit_duplicated_state);
 int drm_atomic_helper_resume(struct drm_device *dev,
 			     struct drm_atomic_state *state)
 {
-	struct drm_mode_config *config = &dev->mode_config;
+	struct drm_modeset_acquire_ctx ctx;
 	int err;
 
 	drm_mode_config_reset(dev);
 
-	drm_modeset_lock_all(dev);
-	err = drm_atomic_helper_commit_duplicated_state(state, config->acquire_ctx);
-	drm_modeset_unlock_all(dev);
+	drm_modeset_acquire_init(&ctx, 0);
+	while (1) {
+		err = drm_atomic_helper_commit_duplicated_state(state, &ctx);
+		if (err != -EDEADLK)
+			break;
+
+		drm_modeset_backoff(&ctx);
+	}
+
+	drm_modeset_drop_locks(&ctx);
+	drm_modeset_acquire_fini(&ctx);
 
 	return err;
 }