linux-kernel - RE: [PATCH/RFC 06/12] drm: rcar-du: lvds: Do not look at ports for identifying bridges

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Message-ID: <TY1PR01MB1770B8EED1043B50ED7AEA12C0DA0@TY1PR01MB1770.jpnprd01.prod.outlook.com>
Date:   Mon, 5 Aug 2019 09:06:38 +0000
From:   Fabrizio Castro <fabrizio.castro@...renesas.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
CC:     Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        Jacopo Mondi <jacopo+renesas@...ndi.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Simon Horman <horms@...ge.net.au>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Chris Paterson <Chris.Paterson2@...esas.com>,
        Biju Das <biju.das@...renesas.com>
Subject: RE: [PATCH/RFC 06/12] drm: rcar-du: lvds: Do not look at ports for
 identifying bridges

Hi Laurent,

Thank you for your feedback!

> From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> Sent: 02 August 2019 09:08
> Subject: Re: [PATCH/RFC 06/12] drm: rcar-du: lvds: Do not look at ports for identifying bridges
> 
> Hi Fabrizio,
> 
> Thank you for the patch.
> 
> On Fri, Aug 02, 2019 at 08:34:03AM +0100, Fabrizio Castro wrote:
> > We may be connected to a dual LVDS display, therefore checking
> > if node != remote_input for identifying bridges is not going to
> > work anymore.
> > We could try to match the ports on the remote end to the LVDS
> > encoders, however the companion LVDS encoder instance doesn't
> > hold a reference to the primary LVDS encoder instance.
> > We know we could be connected to either a bridge, or a panel,
> > therefore look through the registered bridges and panels, until
> > we have a match.
> >
> > Signed-off-by: Fabrizio Castro <fabrizio.castro@...renesas.com>
> > ---
> >  drivers/gpu/drm/rcar-du/rcar_lvds.c | 29 +++--------------------------
> >  1 file changed, 3 insertions(+), 26 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/rcar-du/rcar_lvds.c b/drivers/gpu/drm/rcar-du/rcar_lvds.c
> > index c306fab..2d54ae5 100644
> > --- a/drivers/gpu/drm/rcar-du/rcar_lvds.c
> > +++ b/drivers/gpu/drm/rcar-du/rcar_lvds.c
> > @@ -711,10 +711,7 @@ static int rcar_lvds_parse_dt_companion(struct rcar_lvds *lvds)
> >  static int rcar_lvds_parse_dt(struct rcar_lvds *lvds)
> >  {
> >  	struct device_node *local_output = NULL;
> > -	struct device_node *remote_input = NULL;
> >  	struct device_node *remote = NULL;
> > -	struct device_node *node;
> > -	bool is_bridge = false;
> >  	int ret = 0;
> >
> >  	local_output = of_graph_get_endpoint_by_regs(lvds->dev->of_node, 1, 0);
> > @@ -742,27 +739,8 @@ static int rcar_lvds_parse_dt(struct rcar_lvds *lvds)
> >  		goto done;
> >  	}
> >
> > -	remote_input = of_graph_get_remote_endpoint(local_output);
> > -
> > -	for_each_endpoint_of_node(remote, node) {
> > -		if (node != remote_input) {
> > -			/*
> > -			 * We've found one endpoint other than the input, this
> > -			 * must be a bridge.
> > -			 */
> > -			is_bridge = true;
> > -			of_node_put(node);
> > -			break;
> > -		}
> > -	}
> > -
> > -	if (is_bridge) {
> > -		lvds->next_bridge = of_drm_find_bridge(remote);
> > -		if (!lvds->next_bridge) {
> > -			ret = -EPROBE_DEFER;
> > -			goto done;
> > -		}
> > -
> > +	lvds->next_bridge = of_drm_find_bridge(remote);
> 
> How about using drm_of_find_panel_or_bridge() ?

It sounds like drm_of_find_panel_or_bridge is exactly what we need here, I'll give it a try,
thank you for the pointer!

Thanks,
Fab

> 
> > +	if (lvds->next_bridge) {
> >  		if (lvds->info->quirks & RCAR_LVDS_QUIRK_DUAL_LINK)
> >  			lvds->dual_link = lvds->next_bridge->timings
> >  					? lvds->next_bridge->timings->dual_link
> > @@ -770,7 +748,7 @@ static int rcar_lvds_parse_dt(struct rcar_lvds *lvds)
> >  	} else {
> >  		lvds->panel = of_drm_find_panel(remote);
> >  		if (IS_ERR(lvds->panel)) {
> > -			ret = PTR_ERR(lvds->panel);
> > +			ret = -EPROBE_DEFER;
> >  			goto done;
> >  		}
> >  	}
> > @@ -784,7 +762,6 @@ static int rcar_lvds_parse_dt(struct rcar_lvds *lvds)
> >
> >  done:
> >  	of_node_put(local_output);
> > -	of_node_put(remote_input);
> >  	of_node_put(remote);
> >
> >  	switch (ret) {
> 
> --
> Regards,
> 
> Laurent Pinchart