[PATCH] drm/amd/display: Check all enabled planes in dm_check_crtc_cursor

[Alex Deucher]

On Tue, Sep 12, 2023 at 6:22 AM Michel Dänzer <michel at daenzer.net> wrote:
>
> From: Michel Dänzer <mdaenzer at redhat.com>
>
> It was only checking planes which had any state changes in the same
> commit. However, it also needs to check other enabled planes.
>
> Not doing this meant that a commit might spuriously "succeed", resulting
> in the cursor plane displaying with incorrect scaling. See
> https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3177#note_1824263
> for an example.

This looks correct to me, but someone more familiar with this code
should probably double check me.
Reviewed-by: Alex Deucher <alexander.deucher at amd.com>

>
> Fixes: d1bfbe8a3202 ("amd/display: check cursor plane matches underlying plane")
> Signed-off-by: Michel Dänzer <mdaenzer at redhat.com>
> ---
>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index 88ba8b66de1f..81c9d39567db 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -9836,14 +9836,24 @@ static int dm_check_crtc_cursor(struct drm_atomic_state *state,
>          * blending properties match the underlying planes'.
>          */
>
> -       new_cursor_state = drm_atomic_get_new_plane_state(state, cursor);
> -       if (!new_cursor_state || !new_cursor_state->fb)
> +       new_cursor_state = drm_atomic_get_plane_state(state, cursor);
> +       if (IS_ERR(new_cursor_state))
> +               return PTR_ERR(new_cursor_state);
> +
> +       if (!new_cursor_state->fb)
>                 return 0;
>
>         dm_get_oriented_plane_size(new_cursor_state, &cursor_src_w, &cursor_src_h);
>         cursor_scale_w = new_cursor_state->crtc_w * 1000 / cursor_src_w;
>         cursor_scale_h = new_cursor_state->crtc_h * 1000 / cursor_src_h;
>
> +       /* Need to check all enabled planes, even if this commit doesn't change
> +        * their state
> +        */
> +       i = drm_atomic_add_affected_planes(state, crtc);
> +       if (i)
> +               return i;
> +
>         for_each_new_plane_in_state_reverse(state, underlying, new_underlying_state, i) {
>                 /* Narrow down to non-cursor planes on the same CRTC as the cursor */
>                 if (new_underlying_state->crtc != crtc || underlying == crtc->cursor)
> --
> 2.40.1
>