[PATCH] drm/mediatek: Fix missing configuration flags in mtk_crtc_ddp_config()

[Chun-Kuang Hu]

Hi, Jason:

Jason-JH.Lin <jason-jh.lin at mediatek.com> 於 2024年7月3日 週三 下午6:33寫道：
>
> In mtk_crtc_ddp_config(), mtk_crtc will use some configuration flags to
> generate instructions to cmdq_handle, such as:
>   state->pending_config
>   mtk_crtc->pending_planes
>   plane_state->pending.config
>   mtk_crtc->pending_async_planes
>   plane_state->pending.async_config
>
> These configuration flags may be set to false when a GCE IRQ comes calling
> ddp_cmdq_cb(). This may result in missing prepare instructions,
> especially if mtk_crtc_update_config() with the flase need_vblank (no need
> to wait for vblank) cases.
>
> Therefore, use the mtk_crtc->config_updating flag set at the beginning of
> mtk_crtc_update_config() to ensure that these configuration flags won't be
> changed when the mtk_crtc_ddp_config() is preparing instructions.
>
> Fixes: 7f82d9c43879 ("drm/mediatek: Clear pending flag when cmdq packet is done")
> Signed-off-by: Jason-JH.Lin <jason-jh.lin at mediatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_crtc.c | 34 +++++++++++++++--------------
>  1 file changed, 18 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_crtc.c b/drivers/gpu/drm/mediatek/mtk_crtc.c
> index 6f34f573e127..bc3bf0c3edd9 100644
> --- a/drivers/gpu/drm/mediatek/mtk_crtc.c
> +++ b/drivers/gpu/drm/mediatek/mtk_crtc.c
> @@ -314,30 +314,32 @@ static void ddp_cmdq_cb(struct mbox_client *cl, void *mssg)
>
>         state = to_mtk_crtc_state(mtk_crtc->base.state);
>
> -       state->pending_config = false;
> +       if (!mtk_crtc->config_updating) {
> +               state->pending_config = false;

I think if mtk_crtc->config_updating == true, the whole clear job
could be skipped.
And use spin_lock to protect the clear job in irq.

/*
spin_lock():
if (mtk_crtc->config_updating) {
        spin_unlock();
        goto out;
}

/* clear job */

spin_unlock();
*/
out:

In mtk_crtc_config_update(), use spin_lock to protect mtk_crtc->config_updating:

spin_lock();
mtk_crtc->config_updating = true;
spin_unlock();
...
spin_lock();
mtk_crtc->config_updating = false;
spin_unlock();

Regards,
Chun-Kuang.


>
> -       if (mtk_crtc->pending_planes) {
> -               for (i = 0; i < mtk_crtc->layer_nr; i++) {
> -                       struct drm_plane *plane = &mtk_crtc->planes[i];
> -                       struct mtk_plane_state *plane_state;
> +               if (mtk_crtc->pending_planes) {
> +                       for (i = 0; i < mtk_crtc->layer_nr; i++) {
> +                               struct drm_plane *plane = &mtk_crtc->planes[i];
> +                               struct mtk_plane_state *plane_state;
>
> -                       plane_state = to_mtk_plane_state(plane->state);
> +                               plane_state = to_mtk_plane_state(plane->state);
>
> -                       plane_state->pending.config = false;
> +                               plane_state->pending.config = false;
> +                       }
> +                       mtk_crtc->pending_planes = false;
>                 }
> -               mtk_crtc->pending_planes = false;
> -       }
>
> -       if (mtk_crtc->pending_async_planes) {
> -               for (i = 0; i < mtk_crtc->layer_nr; i++) {
> -                       struct drm_plane *plane = &mtk_crtc->planes[i];
> -                       struct mtk_plane_state *plane_state;
> +               if (mtk_crtc->pending_async_planes) {
> +                       for (i = 0; i < mtk_crtc->layer_nr; i++) {
> +                               struct drm_plane *plane = &mtk_crtc->planes[i];
> +                               struct mtk_plane_state *plane_state;
>
> -                       plane_state = to_mtk_plane_state(plane->state);
> +                               plane_state = to_mtk_plane_state(plane->state);
>
> -                       plane_state->pending.async_config = false;
> +                               plane_state->pending.async_config = false;
> +                       }
> +                       mtk_crtc->pending_async_planes = false;
>                 }
> -               mtk_crtc->pending_async_planes = false;
>         }
>
>         mtk_crtc->cmdq_vblank_cnt = 0;
> --
> 2.18.0
>