linux-kernel - Re: [RESEND PATCH v5 2/3] dt-bindings: display: atmel: optional video-interface of endpoints

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Date:   Fri, 3 Aug 2018 10:11:28 +0200
From:   jacopo mondi <jacopo@...ndi.org>
To:     Peter Rosin <peda@...ntia.se>
Cc:     linux-kernel@...r.kernel.org,
        Boris Brezillon <boris.brezillon@...tlin.com>,
        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>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, Jyri Sarha <jsarha@...com>,
        Daniel Vetter <daniel@...ll.ch>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Jacopo Mondi <jacopo+renesas@...ndi.org>
Subject: Re: [RESEND PATCH v5 2/3] dt-bindings: display: atmel: optional
 video-interface of endpoints

Hi Peter!

On Fri, Aug 03, 2018 at 09:23:07AM +0200, Peter Rosin 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.
>
> Acked-by: Boris Brezillon <boris.brezillon@...tlin.com>
> Reviewed-by: Rob Herring <robh@...nel.org>
> Signed-off-by: Peter Rosin <peda@...ntia.se>
> ---
>  .../devicetree/bindings/display/atmel/hlcdc-dc.txt | 26 ++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/display/atmel/hlcdc-dc.txt b/Documentation/devicetree/bindings/display/atmel/hlcdc-dc.txt
> index 82f2acb3d374..9de434a8f523 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>.

Is there any value in specifying this, if it has a fixed value to
"autodetect"? I understand it's optional, so if nobody else objects,
feels free to keep it there.


> + - bus-width: recognized values are <12>, <16>, <18> and <24>, and
> +   override any output mode selection heuristic, forcing "rgb444",
> +   "rgb565", "rgb666" and "rgb888" respectively.
> +
>  Example:
>
>  	hlcdc: hlcdc@...30000 {
> @@ -50,3 +58,21 @@ Example:
>  			#pwm-cells = <3>;
>  		};
>  	};
> +

Two blank lines here.

> +
> +Example 2: With a video interface override to force rgb565; as above
> +but with these changes/additions:
> +
> +	&hlcdc {
> +		hlcdc-display-controller {
> +			pinctrl-names = "default";
> +			pinctrl-0 = <&pinctrl_lcd_base &pinctrl_lcd_rgb565>;
> +
> +			port@0 {

The node has a unit address specified, you're missing a reg = <0>
property (no big deal, it's an example, but the other one has it)

> +				hlcdc_panel_output: endpoint@0 {

Missing reg here too.

Minors apart:

Reviewed-by: Jacopo Mondi <jacopo+renesas@...ndi.org>

Thanks
   j

> +					bus-type = <0>;
> +					bus-width = <16>;
> +				};
> +			};
> +		};
> +	};
> --
> 2.11.0
>

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