[Intel-gfx] [PATCH 24/28] drm: use new iterator in drm_gem_plane_helper_prepare_fb v2

[Daniel Vetter]

On Tue, Oct 05, 2021 at 01:37:38PM +0200, Christian König wrote:
> Makes the handling a bit more complex, but avoids the use of
> dma_resv_get_excl_unlocked().
> 
> v2: improve coding and documentation
> 
> Signed-off-by: Christian König <christian.koenig at amd.com>
> ---
>  drivers/gpu/drm/drm_gem_atomic_helper.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_gem_atomic_helper.c b/drivers/gpu/drm/drm_gem_atomic_helper.c
> index e570398abd78..8534f78d4d6d 100644
> --- a/drivers/gpu/drm/drm_gem_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_gem_atomic_helper.c
> @@ -143,6 +143,7 @@
>   */
>  int drm_gem_plane_helper_prepare_fb(struct drm_plane *plane, struct drm_plane_state *state)
>  {
> +	struct dma_resv_iter cursor;
>  	struct drm_gem_object *obj;
>  	struct dma_fence *fence;
>  
> @@ -150,9 +151,17 @@ int drm_gem_plane_helper_prepare_fb(struct drm_plane *plane, struct drm_plane_st
>  		return 0;
>  
>  	obj = drm_gem_fb_get_obj(state->fb, 0);
> -	fence = dma_resv_get_excl_unlocked(obj->resv);
> -	drm_atomic_set_fence_for_plane(state, fence);
> +	dma_resv_iter_begin(&cursor, obj->resv, false);
> +	dma_resv_for_each_fence_unlocked(&cursor, fence) {
> +		/* TODO: We only use the first write fence here and need to fix
> +		 * the drm_atomic_set_fence_for_plane() API to accept more than
> +		 * one. */

I'm confused, right now there is only one write fence. So no need to
iterate, and also no need to add a TODO. If/when we add more write fences
then I think this needs to be revisited, and ofc then we do need to update
the set_fence helpers to carry an entire array of fences.
-Daniel

> +		dma_fence_get(fence);
> +		break;
> +	}
> +	dma_resv_iter_end(&cursor);
>  
> +	drm_atomic_set_fence_for_plane(state, fence);
>  	return 0;
>  }
>  EXPORT_SYMBOL_GPL(drm_gem_plane_helper_prepare_fb);
> -- 
> 2.25.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch