Re: [PATCH v4] drm/mediatek: mtk_dsi: Avoid EPROBE_DEFER loop with external bridge

[AngeloGioacchino Del Regno]

Il 08/02/22 09:32, CK Hu ha scritto:
> Hi, Angelo:
>
> On Tue, 2022-02-08 at 16:20 +0800, CK Hu wrote:
> > Hi, Angelo:
> >
> > On Mon, 2022-01-31 at 09:55 +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).
> > >
> > > Cc: <stable@xxxxxxxxxxxxxxx> # 5.15.x
> > > Signed-off-by: AngeloGioacchino Del Regno <
> > > angelogioacchino.delregno@xxxxxxxxxxxxx>
> > > Reviewed-by: Andrzej Hajda <andrzej.hajda@xxxxxxxxx>
> > > Reviewed-by: Jagan Teki <jagan@xxxxxxxxxxxxxxxxxxxx>
> > >
> > > ---
> > >   drivers/gpu/drm/mediatek/mtk_dsi.c | 167 +++++++++++++++----------
> > > ----
> > >   1 file changed, 84 insertions(+), 83 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c
> > > b/drivers/gpu/drm/mediatek/mtk_dsi.c
> > > index 5d90d2eb0019..bced4c7d668e 100644
> > > --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> > > +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> > > @@ -786,18 +786,101 @@ void mtk_dsi_ddp_stop(struct device *dev)
> > >   	mtk_dsi_poweroff(dsi);
> > >   }
> > >   
> >
> > [snip]
> >
> > > +
> > >   static int mtk_dsi_host_attach(struct mipi_dsi_host *host,
> > >   			       struct mipi_dsi_device *device)
> > >   {
> > >   	struct mtk_dsi *dsi = host_to_dsi(host);
> > > +	struct device *dev = host->dev;
> > > +	int ret;
> > >   
> > >   	dsi->lanes = device->lanes;
> > >   	dsi->format = device->format;
> > >   	dsi->mode_flags = device->mode_flags;
> > > +	dsi->next_bridge = devm_drm_of_get_bridge(dev, dev->of_node, 0,
> > > 0);
> >
> > The original would process panel. Why do you remove the panel part?
> > It's better that someone has a platform of DSI->Panel to test this
> > patch.
>
> Sorry, devm_drm_of_get_bridge() has processed the panel part, so for
> this patch,
>
> Reviewed-by: CK Hu <ck.hu@xxxxxxxxxxxx>

No worries! Thanks for the review/approval.

Regards,
Angelo

> > Regards,
> > CK