linux-kernel - Re: [PATCH v1 3/5] drm/mediatek: mtk_drm_drv: Unbind secondary mmsys components on err

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Message-ID: <CAGXv+5H1aww6Adf=EKCkpC8oCkdRLEHP5_fwtfU1BzEsnyi7NA@mail.gmail.com>
Date: Wed, 2 Apr 2025 18:19:24 +0800
From: Chen-Yu Tsai <wenst@...omium.org>
To: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Cc: chunkuang.hu@...nel.org, p.zabel@...gutronix.de, airlied@...il.com, 
	simona@...ll.ch, matthias.bgg@...il.com, nancy.lin@...iatek.com, 
	ck.hu@...iatek.com, djkurtz@...omium.org, littlecvr@...omium.org, 
	bibby.hsieh@...iatek.com, dri-devel@...ts.freedesktop.org, 
	linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, kernel@...labora.com
Subject: Re: [PATCH v1 3/5] drm/mediatek: mtk_drm_drv: Unbind secondary mmsys
 components on err

On Wed, Apr 2, 2025 at 4:36 PM AngeloGioacchino Del Regno
<angelogioacchino.delregno@...labora.com> wrote:
>
> When calling component_bind_all(), if a component that is included
> in the list fails, all of those that have been successfully bound
> will be unbound, but this driver has two components lists for two
> actual devices, as in, each mmsys instance has its own components
> list.
>
> In case mmsys0 (or actually vdosys0) is able to bind all of its
> components, but the secondary one fails, all of the components of
> the first are kept bound, while the ones of mmsys1/vdosys1 are
> correctly cleaned up.
>
> This is not right because, in case of a failure, the components
> are re-bound for all of the mmsys/vdosys instances without caring
> about the ones that were previously left in a bound state.
>
> Fix that by calling component_unbind_all() on all of the previous
> component masters that succeeded binding all subdevices when any
> of the other masters errors out.
>
> Fixes: 1ef7ed48356c ("drm/mediatek: Modify mediatek-drm for mt8195 multi mmsys support")
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>

Makes sense.

Reviewed-by: Chen-Yu Tsai <wenst@...omium.org>

> ---
>  drivers/gpu/drm/mediatek/mtk_drm_drv.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> index 6b31df587507..2d6562b29755 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> @@ -482,8 +482,11 @@ static int mtk_drm_kms_init(struct drm_device *drm)
>         for (i = 0; i < private->data->mmsys_dev_num; i++) {
>                 drm->dev_private = private->all_drm_private[i];
>                 ret = component_bind_all(private->all_drm_private[i]->dev, drm);
> -               if (ret)
> +               if (ret) {
> +                       while (--i >= 0)
> +                               component_unbind_all(private->all_drm_private[i]->dev, drm);
>                         return ret;
> +               }
>         }
>
>         /*
> --
> 2.48.1
>