linux-kernel - Re: [PATCH v2] drm/mediatek: Add wait_event

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Message-ID: <6e7ab8ab603ed8ac06c7a6b639f339c1d87f9ad0.camel@mediatek.com>
Date: Wed, 25 Jun 2025 07:39:54 +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>, "AngeloGioacchino Del
 Regno" <angelogioacchino.delregno@...labora.com>, "airlied@...il.com"
	<airlied@...il.com>
CC: Sirius Wang (王皓昱) <Sirius.Wang@...iatek.com>,
	Nancy Lin (林欣螢) <Nancy.Lin@...iatek.com>,
	Xiandong Wang (王先冬)
	<Xiandong.Wang@...iatek.com>, "daniel@...ll.ch" <daniel@...ll.ch>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
	Paul-pl Chen (陳柏霖) <Paul-pl.Chen@...iatek.com>,
	Zhenxing Qin (秦振兴) <Zhenxing.Qin@...iatek.com>,
	Project_Global_Chrome_Upstream_Group
	<Project_Global_Chrome_Upstream_Group@...iatek.com>,
	Yongqiang Niu (牛永强)
	<yongqiang.niu@...iatek.com>, "p.zabel@...gutronix.de"
	<p.zabel@...gutronix.de>, Singo Chang (張興國)
	<Singo.Chang@...iatek.com>, "wenst@...omium.org" <wenst@...omium.org>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>,
	Jarried Lin (林裕哲) <Jarried.Lin@...iatek.com>,
	Xavier Chang (張獻文) <Xavier.Chang@...iatek.com>,
	"matthias.bgg@...il.com" <matthias.bgg@...il.com>
Subject: Re: [PATCH v2] drm/mediatek: Add wait_event_timeout when disabling
 plane

On Wed, 2025-06-25 at 06:54 +0000, CK Hu (胡俊光) wrote:
> On Tue, 2025-06-24 at 19:31 +0800, Jason-JH Lin wrote:
> > Our hardware registers are set through GCE, not by the CPU.
> > DRM might assume the hardware is disabled immediately after calling
> > atomic_disable() of drm_plane, but it is only truly disabled after
> > the
> > GCE IRQ is triggered.
> > 
> > Additionally, the cursor plane in DRM uses async_commit, so DRM
> > will
> > not wait for vblank and will free the buffer immediately after
> > calling
> > atomic_disable().
> > 
> > To prevent the framebuffer from being freed before the layer
> > disable
> > settings are configured into the hardware, which can cause an IOMMU
> > fault error, a wait_event_timeout has been added to wait for the
> > ddp_cmdq_cb() callback,indicating that the GCE IRQ has been
> > triggered.
> > 
> > Fixes: 119f5173628a ("drm/mediatek: Add DRM Driver for Mediatek SoC
> > MT8173.")
> 
> This patch looks good to me, so
> 
> Reviewed-by: CK Hu <ck.hu@...iatek.com>
> 
> But fixes patch is not correct.
> In "drm/mediatek: Add DRM Driver for Mediatek SoC MT8173.", it does
> not support cmdq.
> The first patch to support cmdq is 2f965be7f900 "drm/mediatek: apply
> CMDQ control flow"
> I would change fixes tag when I apply this patch.
> 

Thank you very much!

Regards,
Jason-JH Lin

> > Signed-off-by: Jason-JH Lin <jason-jh.lin@...iatek.com>
> > Reviewed-by: AngeloGioacchino Del Regno
> > <angelogioacchino.delregno@...labora.com>