linux-kernel - Re: [PATCH v1, 1/1] drm/mediatek: fixup ovl vblank callback data null pointer issue

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Date:   Thu, 17 Mar 2022 20:46:31 +0800
From:   Rex-BC Chen <rex-bc.chen@...iatek.com>
To:     Yongqiang Niu <yongqiang.niu@...iatek.com>,
        Chun-Kuang Hu <chunkuang.hu@...nel.org>
CC:     Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        "David Airlie" <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Jassi Brar <jassisinghbrar@...il.com>,
        Fabien Parent <fparent@...libre.com>,
        "Dennis YC Hsieh" <dennis-yc.hsieh@...iatek.com>,
        <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <Project_Global_Chrome_Upstream_Group@...iatek.com>,
        Hsin-Yi Wang <hsinyi@...omium.org>
Subject: Re: [PATCH v1, 1/1] drm/mediatek: fixup ovl vblank callback data
 null pointer issue

On Mon, 2022-03-14 at 16:08 +0800, Yongqiang Niu wrote:
> ovl vblank_cb_data will be null pointer when disable ovl
> vblank
> 

Hello Yongqiang,

What issue do you encounter?
Is it a timing issue?

> Signed-off-by: Yongqiang Niu <yongqiang.niu@...iatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_disp_ovl.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> index 2146299e5f52..f3a450c0ef2d 100644
> --- a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> +++ b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> @@ -113,7 +113,6 @@ void mtk_ovl_disable_vblank(struct device *dev)
>  	struct mtk_disp_ovl *ovl = dev_get_drvdata(dev);
>  
>  	ovl->vblank_cb = NULL;
> -	ovl->vblank_cb_data = NULL;

IMO, this may be not a good solution.
If this is a timing issue and you don't need to handle irq after
disable vblank.
I think you should handle  ovl->vblank_cb_data == NULL in
mtk_disp_ovl_irq_handler?

If I am wrong, please correct me.

Thanks.

BRs,
Rex

>  	writel_relaxed(0x0, ovl->regs + DISP_REG_OVL_INTEN);
>  }
>