Re: [Intel-gfx] [PATCH] drm/damage_helper: Fix handling of cursor dirty buffers

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Aug 17, 2021 at 04:26:04PM -0700, José Roberto de Souza wrote:
> Cursors don't have a framebuffer so the fb comparisson was always
> failing and atomic state was being committed without any plane state.
> 
> So here checking if objects match when checking cursors.

This looks extremely backwards ... what exactly is this fixing? If this
isn't based on a real world compositor usage but some igt, then I'd say
the igt here is very wrong.
-Daniel

> Fixes: b9fc5e01d1ce ("drm: Add helper to implement legacy dirtyfb")
> Cc: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Rob Clark <robdclark@gmail.com>
> Cc: Deepak Rawat <drawat@vmware.com>
> Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
> Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> ---
>  drivers/gpu/drm/drm_damage_helper.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_damage_helper.c b/drivers/gpu/drm/drm_damage_helper.c
> index 8eeff0c7bdd47..595187d97c131 100644
> --- a/drivers/gpu/drm/drm_damage_helper.c
> +++ b/drivers/gpu/drm/drm_damage_helper.c
> @@ -157,12 +157,18 @@ int drm_atomic_helper_dirtyfb(struct drm_framebuffer *fb,
>  retry:
>  	drm_for_each_plane(plane, fb->dev) {
>  		struct drm_plane_state *plane_state;
> +		bool match;
>  
>  		ret = drm_modeset_lock(&plane->mutex, state->acquire_ctx);
>  		if (ret)
>  			goto out;
>  
> -		if (plane->state->fb != fb) {
> +		match = plane->state->fb == fb;
> +		/* Check if objs match to handle dirty buffers of cursors */
> +		if (plane->type == DRM_PLANE_TYPE_CURSOR && plane->state->fb)
> +			match |= fb->obj[0] == plane->state->fb->obj[0];
> +
> +		if (!match) {
>  			drm_modeset_unlock(&plane->mutex);
>  			continue;
>  		}
> -- 
> 2.32.0
> 

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