linux-kernel - Re: [PATCH 3/3] drm/mediatek: add devlink to cmdq dev

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Message-ID: <YZXqz6XDChwscDC0@google.com>
Date:   Thu, 18 Nov 2021 13:55:27 +0800
From:   Tzung-Bi Shih <tzungbi@...gle.com>
To:     "jason-jh.lin" <jason-jh.lin@...iatek.com>
Cc:     Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Jassi Brar <jassisinghbrar@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org,
        linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        hsinyi@...omium.org, fshao@...omium.org, nancy.lin@...iatek.com,
        singo.chang@...iatek.com
Subject: Re: [PATCH 3/3] drm/mediatek: add devlink to cmdq dev

On Wed, Nov 17, 2021 at 02:41:58PM +0800, jason-jh.lin wrote:
> @@ -158,6 +159,7 @@ static void mtk_drm_crtc_destroy(struct drm_crtc *crtc)
>  	mtk_drm_cmdq_pkt_destroy(&mtk_crtc->cmdq_handle);
>  
>  	if (mtk_crtc->cmdq_client.chan) {
> +		device_link_remove(mtk_crtc->drm_dev, mtk_crtc->cmdq_client.chan->mbox->dev);
>  		mbox_free_channel(mtk_crtc->cmdq_client.chan);
>  		mtk_crtc->cmdq_client.chan = NULL;
>  	}
[...]
> @@ -956,6 +959,16 @@ int mtk_drm_crtc_create(struct drm_device *drm_dev,
>  	}
>  
>  	if (mtk_crtc->cmdq_client.chan) {
> +		struct device_link *link;
> +
> +		/* add devlink to cmdq dev to make sure suspend/resume order is correct */
> +		link = device_link_add(dev, mtk_crtc->cmdq_client.chan->mbox->dev,
> +				       DL_FLAG_PM_RUNTIME | DL_FLAG_STATELESS);
> +		if (!link) {
> +			dev_err(dev, "Unable to link dev=%s\n",
> +				dev_name(mtk_crtc->cmdq_client.chan->mbox->dev));
> +		}
> +

If device_link_add() failed, doesn't mtk_drm_crtc_create() need to return an error and exit?

OTOH, if device_link_add() failed, won't it bring any side effects to call device_link_remove()?