linux-kernel - Re: [PATCH v2] drm/mediatek: Add spinlock for setting vblank event in atomic

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Date:   Wed, 8 Nov 2023 07:27:24 +0000
From:   CK Hu (胡俊光) <ck.hu@...iatek.com>
To:     Jason-JH Lin (林睿祥) 
        <Jason-JH.Lin@...iatek.com>,
        "chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Singo Chang (張興國) 
        <Singo.Chang@...iatek.com>,
        Johnson Wang (王聖鑫) 
        <Johnson.Wang@...iatek.com>,
        Jason-ch Chen (陳建豪) 
        <Jason-ch.Chen@...iatek.com>,
        Shawn Sung (宋孝謙) 
        <Shawn.Sung@...iatek.com>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        Nancy Lin (林欣螢) <Nancy.Lin@...iatek.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        Project_Global_Chrome_Upstream_Group 
        <Project_Global_Chrome_Upstream_Group@...iatek.com>,
        "amergnat@...libre.com" <amergnat@...libre.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "fshao@...omium.org" <fshao@...omium.org>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH v2] drm/mediatek: Add spinlock for setting vblank event in
 atomic_begin

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@...iatek.com>

> 
> Fixes: 119f5173628a ("drm/mediatek: Add DRM Driver for Mediatek SoC
> MT8173.")
> Signed-off-by: Jason-JH.Lin <jason-jh.lin@...iatek.com>
> Suggested-by: AngeloGioacchino Del Regno <
> angelogioacchino.delregno@...labora.com>
> Reviewed-by: Alexandre Mergnat <amergnat@...libre.com>
> Reviewed-by: Fei Shao <fshao@...omium.org>
> Tested-by: Fei Shao <fshao@...omium.org>
> ---
>  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;
>  	}
>  }