Re: [PATCH v2] drm/mediatek: mtk_dsi: Avoid EPROBE_DEFER loop with external bridge

[AngeloGioacchino Del Regno]

Il 06/01/22 06:22, CK Hu ha scritto:
> Hi, Angelo:
>
> On Tue, 2022-01-04 at 10:59 +0100, AngeloGioacchino Del Regno 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).
>
> This patch looks good to me, but please add 'Fixes' tag to note to
> which patch this patch want to fix.
>
> Regards,
> CK

Hello,
unfortunately I couldn't find a valid commit for a Fixes tag. This
started being an issue at some point, when the DRM API was changed to
adhere to the documented probe sequence: the MediaTek DSI driver was
not the only one that got broken/affected by these changes.

If you have any advice on which commit should be tagged, I'm open for
any kind of suggestion.

Thanks,
- Angelo