drm/virtio: track virtual output state

Track whenever an virtual output (crtc) is enabled or disabled.

On atomic updates check for both framebuffer being present and crtc
being enabled to figure whenever the output is active or not.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20180813152855.12863-1-kraxel@redhat.com

drivers/gpu/drm/virtio/virtgpu_display.c

@@ -109,6 +109,9 @@ static void virtio_gpu_crtc_mode_set_nofb(struct drm_crtc *crtc)
 static void virtio_gpu_crtc_atomic_enable(struct drm_crtc *crtc,
 					  struct drm_crtc_state *old_state)
 {
+	struct virtio_gpu_output *output = drm_crtc_to_virtio_gpu_output(crtc);
+
+	output->enabled = true;
 }
 
 static void virtio_gpu_crtc_atomic_disable(struct drm_crtc *crtc,
@@ -119,6 +122,7 @@ static void virtio_gpu_crtc_atomic_disable(struct drm_crtc *crtc,
 	struct virtio_gpu_output *output = drm_crtc_to_virtio_gpu_output(crtc);
 
 	virtio_gpu_cmd_set_scanout(vgdev, output->index, 0, 0, 0, 0, 0);
+	output->enabled = false;
 }
 
 static int virtio_gpu_crtc_atomic_check(struct drm_crtc *crtc,

drivers/gpu/drm/virtio/virtgpu_drv.h

@@ -114,6 +114,7 @@ struct virtio_gpu_output {
 	struct virtio_gpu_update_cursor cursor;
 	int cur_x;
 	int cur_y;
+	bool enabled;
 };
 #define drm_crtc_to_virtio_gpu_output(x) \
 	container_of(x, struct virtio_gpu_output, crtc)

drivers/gpu/drm/virtio/virtgpu_plane.c

@@ -152,7 +152,7 @@ static void virtio_gpu_primary_plane_update(struct drm_plane *plane,
 	if (WARN_ON(!output))
 		return;
 
-	if (plane->state->fb) {
+	if (plane->state->fb && output->enabled) {
 		vgfb = to_virtio_gpu_framebuffer(plane->state->fb);
 		bo = gem_to_virtio_gpu_obj(vgfb->base.obj[0]);
 		handle = bo->hw_res_handle;