Re: FW: [PATCH 3/3] drm/mediatek: add devlink to cmdq dev

[Jason-JH Lin <jason-jh.lin@mediatek.com>]

Hi Tzung-Bi,

Thanks for the reviews.

> From: Linux-mediatek <linux-mediatek-bounces@lists.infradead.org> On
> Behalf Of Tzung-Bi Shih
> Sent: Thursday, November 18, 2021 1:55 PM
> To: Jason-JH Lin (林睿祥) <Jason-JH.Lin@mediatek.com>
> Cc: Chun-Kuang Hu <chunkuang.hu@kernel.org>; Philipp Zabel <
> p.zabel@pengutronix.de>; Matthias Brugger <matthias.bgg@gmail.com>;
> Jassi Brar <jassisinghbrar@gmail.com>; David Airlie <airlied@linux.ie
> >; Daniel Vetter <daniel@ffwll.ch>; dri-devel@lists.freedesktop.org; 
> linux-mediatek@lists.infradead.org; 
> linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org; 
> hsinyi@chromium.org; fshao@chromium.org; Nancy Lin (林欣螢) <
> Nancy.Lin@mediatek.com>; Singo Chang (張興國) <Singo.Chang@mediatek.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?

OK, I'll add the return error at the next verion.
> 
> OTOH, if device_link_add() failed, won't it bring any side effects to
> call device_link_remove()?
> 

Because device_link_remove() will find the device_link of supplier and
consumer, then delete the device_link between them.
If device_link_add() failed, supplier and consumer won't create the
device_link.
So calling device_link_remove() won't do anything without deive_link
and won't bring any side effects.

Regards,
Jason-JH.Lin
> _______________________________________________
> Linux-mediatek mailing list
> Linux-mediatek@lists.infradead.org
> 
https://urldefense.com/v3/__http://lists.infradead.org/mailman/listinfo/linux-mediatek__;!!CTRNKA9wMg0ARbw!125dmOZ7xCLkwbIrzZf1VqVLQBbdT4RFHoMjR38U1GeCxaTM6xvvB-mSr7sTc6BuY5IH$
>  
-- 
Jason-JH Lin <jason-jh.lin@mediatek.com>