drm: Roll out acquire context for the page_flip ioctl

Again just prep work.
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170322215058.8671-11-daniel.vetter@ffwll.ch

drivers/gpu/drm/drm_plane.c

@@ -803,6 +803,7 @@ int drm_mode_page_flip_ioctl(struct drm_device *dev,
 	struct drm_framebuffer *fb = NULL;
 	struct drm_pending_vblank_event *e = NULL;
 	u32 target_vblank = page_flip->sequence;
+	struct drm_modeset_acquire_ctx ctx;
 	int ret = -EINVAL;
 
 	if (!drm_core_check_feature(dev, DRIVER_MODESET))
@@ -866,7 +867,16 @@ int drm_mode_page_flip_ioctl(struct drm_device *dev,
 		return -EINVAL;
 	}
 
-	drm_modeset_lock_crtc(crtc, crtc->primary);
+	drm_modeset_acquire_init(&ctx, 0);
+retry:
+	ret = drm_modeset_lock(&crtc->mutex, &ctx);
+	if (ret)
+		goto out;
+	ret = drm_modeset_lock(&crtc->cursor->mutex, &ctx);
+	if (ret)
+		goto out;
+	crtc->acquire_ctx = &ctx;
+
 	if (crtc->primary->fb == NULL) {
 		/* The framebuffer is currently unbound, presumably
 		 * due to a hotplug event, that userspace has not
@@ -944,7 +954,14 @@ int drm_mode_page_flip_ioctl(struct drm_device *dev,
 	if (crtc->primary->old_fb)
 		drm_framebuffer_put(crtc->primary->old_fb);
 	crtc->primary->old_fb = NULL;
-	drm_modeset_unlock_crtc(crtc);
+
+	if (ret == -EDEADLK) {
+		drm_modeset_backoff(&ctx);
+		goto retry;
+	}
+
+	drm_modeset_drop_locks(&ctx);
+	drm_modeset_acquire_fini(&ctx);
 
 	return ret;
 }