linux-kernel - Re: [PATCH v2] drm/mediatek: mtk_dsi: Avoid EPROBE

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Date:   Thu, 27 Jan 2022 22:21:35 +0800
From:   Chun-Kuang Hu <chunkuang.hu@...nel.org>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
Cc:     Jagan Teki <jagan@...rulasolutions.com>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        David Airlie <airlied@...ux.ie>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        andrzej.hajda@...el.com,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Collabora Kernel ML <kernel@...labora.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2] drm/mediatek: mtk_dsi: Avoid EPROBE_DEFER loop with
 external bridge

Hi, Angelo:

AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com> 於
2022年1月27日 週四 下午6:32寫道：
>
> Il 12/01/22 08:09, Jagan Teki ha scritto:
> > On Tue, Jan 4, 2022 at 3:30 PM AngeloGioacchino Del Regno
> > <angelogioacchino.delregno@...labora.com> wrote:
> >>
> >> DRM bridge drivers are now attaching their DSI device at probe time,
> >> which requires us to register our DSI host in order to let the bridge
> >> to probe: this recently started producing an endless -EPROBE_DEFER
> >> loop on some machines that are using external bridges, like the
> >> parade-ps8640, found on the ACER Chromebook R13.
> >>
> >> Now that the DSI hosts/devices probe sequence is documented, we can
> >> do adjustments to the mtk_dsi driver as to both fix now and make sure
> >> to avoid this situation in the future: for this, following what is
> >> documented in drm_bridge.c, move the mtk_dsi component_add() to the
> >> mtk_dsi_ops.attach callback and delete it in the detach callback;
> >> keeping in mind that we are registering a drm_bridge for our DSI,
> >> which is only used/attached if the DSI Host is bound, it wouldn't
> >> make sense to keep adding our bridge at probe time (as it would
> >> be useless to have it if mtk_dsi_ops.attach() fails!), so also move
> >> that one to the dsi host attach function (and remove it in detach).
> >>
> >> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> >> Reviewed-by: Andrzej Hajda <andrzej.hajda@...el.com>
> >> ---
> >
> > Eventually I've observed similar issue on other Component based DSI
> > controllers, hence
> >
> > Reviewed-by: Jagan Teki <jagan@...rulasolutions.com>
> >
>
> Hello dri-devel,
> can you please pick this patch?
>
> All MediaTek platforms are broken in v5.17 without this one.

Please add Fixes tag [1] to this patch.

[1] https://www.kernel.org/doc/html/v5.16/process/submitting-patches.html

Regards,
Chun-Kuang.

>
> Thanks,
> Angelo