linux-kernel - Re: [PATCH v2] drm/mediatek: Move mtk_crtc_finish_page_flip() to ddp_cmdq

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Message-ID: <b7398d1fb0d5ee96acf3587c44379b3f639a9a38.camel@mediatek.com>
Date: Tue, 10 Dec 2024 01:45:45 +0000
From: Jason-JH Lin (林睿祥) <Jason-JH.Lin@...iatek.com>
To: CK Hu (胡俊光) <ck.hu@...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>,
	"linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
	Shawn Sung (宋孝謙) <Shawn.Sung@...iatek.com>,
	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>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "fshao@...omium.org"
	<fshao@...omium.org>, AngeloGioacchino Del Regno
	<angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH v2] drm/mediatek: Move mtk_crtc_finish_page_flip() to
 ddp_cmdq_cb()

Hi CK,

Thanks for the review.

[snip]

> >  static void mtk_drm_finish_page_flip(struct mtk_crtc *mtk_crtc)
> >  {
> >  	unsigned long flags;
> > +	struct drm_crtc *crtc = &mtk_crtc->base;
> > +	struct mtk_drm_private *priv = crtc->dev->dev_private;
> >  
> >  	drm_crtc_handle_vblank(&mtk_crtc->base);
> >  
> > -	spin_lock_irqsave(&mtk_crtc->config_lock, flags);
> > -	if (!mtk_crtc->config_updating && mtk_crtc-
> > >pending_needs_vblank) {
> > -		mtk_crtc_finish_page_flip(mtk_crtc);
> > -		mtk_crtc->pending_needs_vblank = false;
> > +	if (priv->data->shadow_register) {
> 
> if (!priv->data->shadow_register)
> 	return;
> 
> And this would reduce the indent.
> 

OK, I'll adjust this.

> > +		spin_lock_irqsave(&mtk_crtc->config_lock, flags);
> > +		if (!mtk_crtc->config_updating && mtk_crtc-
> > >pending_needs_vblank) {
> > +			mtk_crtc_finish_page_flip(mtk_crtc);
> > +			mtk_crtc->pending_needs_vblank = false;
> > +		}
> > +		spin_unlock_irqrestore(&mtk_crtc->config_lock, flags);
> >  	}
> > -	spin_unlock_irqrestore(&mtk_crtc->config_lock, flags);
> >  }
> >  
> >  static void mtk_crtc_destroy(struct drm_crtc *crtc)
> > @@ -284,10 +288,8 @@ static void ddp_cmdq_cb(struct mbox_client
> > *cl, void *mssg)
> >  	state = to_mtk_crtc_state(mtk_crtc->base.state);
> >  
> >  	spin_lock_irqsave(&mtk_crtc->config_lock, flags);
> > -	if (mtk_crtc->config_updating) {
> > -		spin_unlock_irqrestore(&mtk_crtc->config_lock, flags);
> > +	if (mtk_crtc->config_updating)
> >  		goto ddp_cmdq_cb_out;
> > -	}
> >  
> >  	state->pending_config = false;
> >  
> > @@ -315,10 +317,15 @@ static void ddp_cmdq_cb(struct mbox_client
> > *cl, void *mssg)
> >  		mtk_crtc->pending_async_planes = false;
> >  	}
> >  
> > -	spin_unlock_irqrestore(&mtk_crtc->config_lock, flags);
> > -
> >  ddp_cmdq_cb_out:
> >  
> > +	if (mtk_crtc->pending_needs_vblank) {
> > +		mtk_crtc_finish_page_flip(mtk_crtc);
> > +		mtk_crtc->pending_needs_vblank = false;
> 
> In mtk_crtc_update_config(), after mbox_client_txdone() and before
> mtk_crtc->config_updating = false;
> cmdq may have finish the command and callback ddp_cmdq_cb().
> Because mtk_crtc->config_updating is true, so this page flip would be
> skipped.
> But if there is no next mtk_crtc_update_config() exist, this page
> flip would never happen.
> This may cause some deadlock.
> 

OK, I'll move the mtk_crtc->config_updating = false; earlier than 
mbox_client_txdone() to avoid skipping the page flip.

Regards,
Jason-JH.Lin

> Regards,
> CK