linux-kernel - Re: [PATCH] drm/mediatek: dsi: Fix DSI host and panel bridge pre-enable order

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Message-ID: <7de3ce656c7fd2f53948abc862a222719b7bce0f.camel@mediatek.com>
Date: Thu, 3 Jul 2025 06:51:10 +0000
From: CK Hu (胡俊光) <ck.hu@...iatek.com>
To: "tzimmermann@...e.de" <tzimmermann@...e.de>, "chunkuang.hu@...nel.org"
	<chunkuang.hu@...nel.org>, "simona@...ll.ch" <simona@...ll.ch>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	"airlied@...il.com" <airlied@...il.com>, "a-bhatia1@...com"
	<a-bhatia1@...com>, "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
	"matthias.bgg@...il.com" <matthias.bgg@...il.com>, Louis-Alexis Eyraud
	<louisalexis.eyraud@...labora.com>, "mripard@...nel.org"
	<mripard@...nel.org>, "tomi.valkeinen@...asonboard.com"
	<tomi.valkeinen@...asonboard.com>, "lumag@...nel.org" <lumag@...nel.org>
CC: "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "kernel@...labora.com"
	<kernel@...labora.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/mediatek: dsi: Fix DSI host and panel bridge
 pre-enable order

On Tue, 2025-07-01 at 09:30 +0200, Louis-Alexis Eyraud wrote:
> External email : Please do not click links or open attachments until you have verified the sender or the content.
> 
> 
> Since commit c9b1150a68d9 ("drm/atomic-helper: Re-order bridge chain
> pre-enable and post-disable"), the bridge pre_enable callbacks are now
> called before crtc enable, and the bridge post_disable callbacks after
> the crtc disable.
> In the mediatek-drm driver, this change leads to transfer errors on
> mtk_dsi_host_transfer callback processing during the panel bridge
> pre-enable sequence because the DSI host bridge pre_enable and CRTC
> enable sequences, that are enabling the required clocks and PHY using
> mtk_dsi_poweron function, are called after.
> 
> So, in order to fix this call order issue, request the DSI host bridge
> be pre-enabled before panel bridge by setting pre_enable_prev_first
> flag on DSI device bridge in the mtk_dsi_host_attach function.

Reviewed-by: CK Hu <ck.hu@...iatek.com>

> 
> Fixes: c9b1150a68d9 ("drm/atomic-helper: Re-order bridge chain pre-enable and post-disable")
> Signed-off-by: Louis-Alexis Eyraud <louisalexis.eyraud@...labora.com>
> ---
>