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

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Message-ID: <27b09cde-2da2-49cf-b872-31adf7b5c4e6@collabora.com>
Date: Tue, 1 Jul 2025 10:19:28 +0200
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: Louis-Alexis Eyraud <louisalexis.eyraud@...labora.com>,
 Chun-Kuang Hu <chunkuang.hu@...nel.org>,
 Philipp Zabel <p.zabel@...gutronix.de>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, Matthias Brugger <matthias.bgg@...il.com>,
 Aradhya Bhatia <a-bhatia1@...com>, Thomas Zimmermann <tzimmermann@...e.de>,
 Dmitry Baryshkov <lumag@...nel.org>, Maxime Ripard <mripard@...nel.org>,
 Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Cc: kernel@...labora.com, dri-devel@...ts.freedesktop.org,
 linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] drm/mediatek: dsi: Fix DSI host and panel bridge
 pre-enable order

Il 01/07/25 09:30, Louis-Alexis Eyraud ha scritto:
> 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.
> 
> Fixes: c9b1150a68d9 ("drm/atomic-helper: Re-order bridge chain pre-enable and post-disable")
> Signed-off-by: Louis-Alexis Eyraud <louisalexis.eyraud@...labora.com>

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

> ---
> This patch fixes an issue that can be observed on boards such as
> MediatekGenio 1200-EVK or 350-EVK with a kernel based on linux-next
> (tag: next-20250635) since commit c9b1150a68d9 ("drm/atomic-helper:
> Re-order bridge chain pre-enable and post-disable").
> In boot logs, there are multiples errors such as IRQ timeouts and
> panel init errors, leading the DSI panel not being enabled:
> 
> Example on Genio 1200-EVK:
> ```
> [drm] Wait DSI IRQ(0x00000002) Timeout
> panel-himax-hx8279 1c008000.dsi.0: sending generic data b0 05 failed:
>    -62
> [drm] Wait DSI IRQ(0x00000008) Timeout
> [drm:mtk_dsi_host_transfer [mediatek_drm]] *ERROR* failed to switch cmd
>   mode
> panel-himax-hx8279 1c008000.dsi.0: sending DCS SET_DISPLAY_ON failed:
>    -62
> ```
> ---
>   drivers/gpu/drm/mediatek/mtk_dsi.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index d7726091819c4762698b41060b3d4d8d27940238..0e2bcd5f67b767d92f2697a5b8183f67ee178a38 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> @@ -1002,6 +1002,12 @@ static int mtk_dsi_host_attach(struct mipi_dsi_host *host,
>   			return PTR_ERR(dsi->next_bridge);
>   	}
>   
> +	/*
> +	 * set flag to request the DSI host bridge be pre-enabled before device bridge
> +	 * in the chain, so the DSI host is ready when the device bridge is pre-enabled
> +	 */
> +	dsi->next_bridge->pre_enable_prev_first = true;
> +
>   	drm_bridge_add(&dsi->bridge);
>   
>   	ret = component_add(host->dev, &mtk_dsi_component_ops);
> 
> ---
> base-commit: c6a68d8f7b81a6ce8962885408cc2d0c1f8b9470
> change-id: 20250630-mediatek-drm-fix-dsi-panel-init-1a4b534c40a6
> 
> Best regards,