linux-kernel - Re: [PATCH/RFC 07/12] drm: rcar-du: lvds: Add support for dual link panels

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Date:   Fri, 2 Aug 2019 11:20:20 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Fabrizio Castro <fabrizio.castro@...renesas.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, linux-renesas-soc@...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 07/12] drm: rcar-du: lvds: Add support for dual link
 panels

Hi Fabrizio,

Thank you for the patch.

On Fri, Aug 02, 2019 at 08:34:04AM +0100, Fabrizio Castro wrote:
> If the display comes with two ports, assume it supports dual
> link.
> 
> Signed-off-by: Fabrizio Castro <fabrizio.castro@...renesas.com>
> ---
>  drivers/gpu/drm/rcar-du/rcar_lvds.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/rcar-du/rcar_lvds.c b/drivers/gpu/drm/rcar-du/rcar_lvds.c
> index 2d54ae5..97c51c2 100644
> --- a/drivers/gpu/drm/rcar-du/rcar_lvds.c
> +++ b/drivers/gpu/drm/rcar-du/rcar_lvds.c
> @@ -751,6 +751,9 @@ static int rcar_lvds_parse_dt(struct rcar_lvds *lvds)
>  			ret = -EPROBE_DEFER;
>  			goto done;
>  		}
> +		if (lvds->info->quirks & RCAR_LVDS_QUIRK_DUAL_LINK)
> +			lvds->dual_link = of_graph_get_endpoint_count(remote)
> +					== 2;

This is a bit of a hack, as I think the information should be queried
from the panel, like we do for bridges. I'd say we can live with this
for now, but as the data swap flag should come from the panel as well,
we will need infrastructure for that, and we can as well through the
dual link flag there at the same time.

I think we should use the drm_bridge_timings structure for this purpose,
as it would make life more difficult for users of drm_bridge and
drm_panel to have two different structures (especially when wrapping a
drm_panel with drm_panel_bridge_add()). The structure could be renamed
if desired.

>  	}
>  
>  	if (lvds->dual_link) {

-- 
Regards,

Laurent Pinchart