Linux Virtualization - Jun 2019 - [PATCH 3/4] drm/virtio: simplify cursor updates

No need to do the reservation dance,
we can just wait on the fence directly.

Signed-off-by: Gerd Hoffmann <kraxel at redhat.com>
---
 drivers/gpu/drm/virtio/virtgpu_plane.c | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_plane.c
b/drivers/gpu/drm/virtio/virtgpu_plane.c
index 024c2aa0c929..4b805bf466d3 100644
--- a/drivers/gpu/drm/virtio/virtgpu_plane.c
+++ b/drivers/gpu/drm/virtio/virtgpu_plane.c
@@ -184,7 +184,6 @@ static void virtio_gpu_cursor_plane_update(struct drm_plane
*plane,
 	struct virtio_gpu_framebuffer *vgfb;
 	struct virtio_gpu_object *bo = NULL;
 	uint32_t handle;
-	int ret = 0;
 
 	if (plane->state->crtc)
 		output = drm_crtc_to_virtio_gpu_output(plane->state->crtc);
@@ -208,15 +207,9 @@ static void virtio_gpu_cursor_plane_update(struct drm_plane
*plane,
 			 cpu_to_le32(plane->state->crtc_w),
 			 cpu_to_le32(plane->state->crtc_h),
 			 0, 0, vgfb->fence);
-		ret = virtio_gpu_object_reserve(bo, false);
-		if (!ret) {
-			reservation_object_add_excl_fence(bo->tbo.resv,
-							  &vgfb->fence->f);
-			dma_fence_put(&vgfb->fence->f);
-			vgfb->fence = NULL;
-			virtio_gpu_object_unreserve(bo);
-			virtio_gpu_object_wait(bo, false);
-		}
+		dma_fence_wait(&vgfb->fence->f, true);
+		dma_fence_put(&vgfb->fence->f);
+		vgfb->fence = NULL;
 	}
 
 	if (plane->state->fb != old_state->fb) {
-- 
2.18.1

On Mon, Jun 17, 2019 at 01:14:05PM +0200, Gerd Hoffmann
wrote:
> No need to do the reservation dance,
> we can just wait on the fence directly.
> 
> Signed-off-by: Gerd Hoffmann <kraxel at redhat.com>
> ---
>  drivers/gpu/drm/virtio/virtgpu_plane.c | 13 +++----------
>  1 file changed, 3 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/virtio/virtgpu_plane.c
b/drivers/gpu/drm/virtio/virtgpu_plane.c
> index 024c2aa0c929..4b805bf466d3 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_plane.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_plane.c
> @@ -184,7 +184,6 @@ static void virtio_gpu_cursor_plane_update(struct
drm_plane *plane,
>  	struct virtio_gpu_framebuffer *vgfb;
>  	struct virtio_gpu_object *bo = NULL;
>  	uint32_t handle;
> -	int ret = 0;
>  
>  	if (plane->state->crtc)
>  		output = drm_crtc_to_virtio_gpu_output(plane->state->crtc);
> @@ -208,15 +207,9 @@ static void virtio_gpu_cursor_plane_update(struct
drm_plane *plane,
>  			 cpu_to_le32(plane->state->crtc_w),
>  			 cpu_to_le32(plane->state->crtc_h),
>  			 0, 0, vgfb->fence);
> -		ret = virtio_gpu_object_reserve(bo, false);
> -		if (!ret) {
> -			reservation_object_add_excl_fence(bo->tbo.resv,
> -							  &vgfb->fence->f);
> -			dma_fence_put(&vgfb->fence->f);
> -			vgfb->fence = NULL;
> -			virtio_gpu_object_unreserve(bo);
> -			virtio_gpu_object_wait(bo, false);
> -		}
> +		dma_fence_wait(&vgfb->fence->f, true);
> +		dma_fence_put(&vgfb->fence->f);
> +		vgfb->fence = NULL;
Even nicer would be to add the fence using
drm_atomic_set_fence_for_plane() in the prepare_fb hook. Assuming this
isn't necessary for correctness (but then I kinda have questions about
races and stuff).

But this gets the job done too I think, so:

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
>  	}
>  
>  	if (plane->state->fb != old_state->fb) {
> -- 
> 2.18.1
> 
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

> Even nicer would be to add the fence using
> drm_atomic_set_fence_for_plane() in the prepare_fb hook. Assuming this
> isn't necessary for correctness (but then I kinda have questions about
> races and stuff).
I'll have a look.  Maybe this way I can drop struct
virtio_gpu_framebuffer (where the fence is the only
thing beside struct drm_framebuffer).

cheers,
  Gerd