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

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Message-ID: <aed94e06-455f-4aa3-8740-57bd1facad22@collabora.com>
Date: Thu, 22 May 2025 12:30:36 +0200
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: Jason-JH Lin <jason-jh.lin@...iatek.com>,
 Chun-Kuang Hu <chunkuang.hu@...nel.org>
Cc: Nancy Lin <nancy.lin@...iatek.com>, Singo Chang
 <singo.chang@...iatek.com>, Paul-PL Chen <paul-pl.chen@...iatek.com>,
 Yongqiang Niu <yongqiang.niu@...iatek.com>,
 Zhenxing Qin <zhenxing.qin@...iatek.com>,
 Sirius Wang <sirius.wang@...iatek.com>,
 Xavier Chang <xavier.chang@...iatek.com>, Fei Shao <fshao@...omium.org>,
 Chen-yu Tsai <wenst@...omium.org>, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, linux-mediatek@...ts.infradead.org,
 linux-arm-kernel@...ts.infradead.org,
 Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH] drm/mediatek: Add wait_event_timeout when disabling plane

Il 22/05/25 10:34, Jason-JH Lin ha scritto:
> 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.")
> Signed-off-by: Jason-JH Lin <jason-jh.lin@...iatek.com>

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>