Re: [PATCH v2] drm/mediatek: Add spinlock for setting vblank event in atomic_begin

[Chen-Yu Tsai]

On Wed, Nov 8, 2023 at 3:27 PM CK Hu (胡俊光) <ck.hu@xxxxxxxxxxxx> wrote:
>
> Hi, Jason:
>
> On Wed, 2023-09-20 at 17:06 +0800, Jason-JH.Lin wrote:
> > Add spinlock protection to avoid race condition on vblank event
> > between mtk_drm_crtc_atomic_begin() and mtk_drm_finish_page_flip().
>
> Reviewed-by: CK Hu <ck.hu@xxxxxxxxxxxx>

Please also merge this for fixes so it lands sooner.

> >
> > Fixes: 119f5173628a ("drm/mediatek: Add DRM Driver for Mediatek SoC
> > MT8173.")
> > Signed-off-by: Jason-JH.Lin <jason-jh.lin@xxxxxxxxxxxx>
> > Suggested-by: AngeloGioacchino Del Regno <
> > angelogioacchino.delregno@xxxxxxxxxxxxx>
> > Reviewed-by: Alexandre Mergnat <amergnat@xxxxxxxxxxxx>
> > Reviewed-by: Fei Shao <fshao@xxxxxxxxxxxx>
> > Tested-by: Fei Shao <fshao@xxxxxxxxxxxx>
> > ---
> >  drivers/gpu/drm/mediatek/mtk_drm_crtc.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> > b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> > index b6fa4ad2f94d..cab4fe092f13 100644
> > --- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> > +++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> > @@ -744,6 +744,7 @@ static void mtk_drm_crtc_atomic_begin(struct
> > drm_crtc *crtc,
> >
> >   crtc);
> >       struct mtk_crtc_state *mtk_crtc_state =
> > to_mtk_crtc_state(crtc_state);
> >       struct mtk_drm_crtc *mtk_crtc = to_mtk_crtc(crtc);
> > +     unsigned long flags;
> >
> >       if (mtk_crtc->event && mtk_crtc_state->base.event)
> >               DRM_ERROR("new event while there is still a pending
> > event\n");
> > @@ -751,7 +752,11 @@ static void mtk_drm_crtc_atomic_begin(struct
> > drm_crtc *crtc,
> >       if (mtk_crtc_state->base.event) {
> >               mtk_crtc_state->base.event->pipe =
> > drm_crtc_index(crtc);
> >               WARN_ON(drm_crtc_vblank_get(crtc) != 0);
> > +
> > +             spin_lock_irqsave(&crtc->dev->event_lock, flags);
> >               mtk_crtc->event = mtk_crtc_state->base.event;
> > +             spin_unlock_irqrestore(&crtc->dev->event_lock, flags);
> > +
> >               mtk_crtc_state->base.event = NULL;
> >       }
> >  }