linux-kernel - Re: [PATCH v2 2/6] dt-bindings: display: atmel: optional video-interface of endpoints

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Date:   Wed, 18 Apr 2018 09:16:58 +0200
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Peter Rosin <peda@...ntia.se>
Cc:     linux-kernel@...r.kernel.org, David Airlie <airlied@...ux.ie>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Gustavo Padovan <gustavo@...ovan.org>,
        Sean Paul <seanpaul@...omium.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 2/6] dt-bindings: display: atmel: optional
 video-interface of endpoints

Hi Peter,

On Tue, 17 Apr 2018 15:10:48 +0200
Peter Rosin <peda@...ntia.se> wrote:

> With bus-type/bus-width properties in the endpoint nodes, the video-
> interface of the connection can be specified for cases where the
> heuristic fails to select the correct output mode. This can happen
> e.g. if not all RGB pins are routed on the PCB; the driver has no
> way of knowing this, and needs to be told explicitly.
> 
> This is critical for the devices that have the "conflicting output
> formats" issue (SAM9N12, SAM9X5, SAMA5D3), since the most significant
> RGB bits move around depending on the selected output mode. For
> devices that do not have the "conflicting output formats" issue
> (SAMA5D2, SAMA5D4), this is completely irrelevant.
> 
> Signed-off-by: Peter Rosin <peda@...ntia.se>
> ---
>  Documentation/devicetree/bindings/display/atmel/hlcdc-dc.txt | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/display/atmel/hlcdc-dc.txt b/Documentation/devicetree/bindings/display/atmel/hlcdc-dc.txt
> index 82f2acb3d374..244b48869eb4 100644
> --- a/Documentation/devicetree/bindings/display/atmel/hlcdc-dc.txt
> +++ b/Documentation/devicetree/bindings/display/atmel/hlcdc-dc.txt
> @@ -15,6 +15,14 @@ Required children nodes:
>   to external devices using the OF graph reprensentation (see ../graph.txt).
>   At least one port node is required.
>  
> +Optional properties in grandchild nodes:
> + Any endpoint grandchild node may specify a desired video interface
> + according to ../../media/video-interfaces.txt, specifically
> + - bus-type: must be <0>.
> + - bus-width: recognized values are <12>, <16>, <18> and <24>, and
> +   override any output mode selection hueristic, forcing "rgb444",
> +   "rgb565", "rgb666" and "rgb888" respectively.
> +

Can you add an example or update the existing one to show how this
should be defined?

>  Example:
>  
>  	hlcdc: hlcdc@...30000 {


Thanks,

Boris