linux-kernel - Re: [PATCH 1/3] dt-bindings: display: bridge: Document THC63LVD1024 LVDS decoder

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Date:   Fri, 9 Mar 2018 09:01:24 +0100
From:   Andrzej Hajda <a.hajda@...sung.com>
To:     Jacopo Mondi <jacopo+renesas@...ndi.org>, architt@...eaurora.org,
        Laurent.pinchart@...asonboard.com, airlied@...ux.ie,
        horms@...ge.net.au, magnus.damm@...il.com, geert@...ux-m68k.org,
        niklas.soderlund@...natech.se, sergei.shtylyov@...entembedded.com,
        robh+dt@...nel.org, mark.rutland@....com
Cc:     dri-devel@...ts.freedesktop.org, linux-renesas-soc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] dt-bindings: display: bridge: Document THC63LVD1024
 LVDS decoder

On 08.03.2018 16:24, Jacopo Mondi wrote:
> Document Thine THC63LVD1024 LVDS decoder.
>
> Signed-off-by: Jacopo Mondi <jacopo+renesas@...ndi.org>
> ---
>  .../bindings/display/bridge/thine,thc63lvd1024.txt | 59 ++++++++++++++++++++++
>  1 file changed, 59 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/display/bridge/thine,thc63lvd1024.txt
>
> diff --git a/Documentation/devicetree/bindings/display/bridge/thine,thc63lvd1024.txt b/Documentation/devicetree/bindings/display/bridge/thine,thc63lvd1024.txt
> new file mode 100644
> index 0000000..53b6453
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/bridge/thine,thc63lvd1024.txt
> @@ -0,0 +1,59 @@
> +THine Electronics THC63LVD1024 LVDS receiver
> +--------------------------------------------
> +
> +The THC63LVD1024 is an LVDS receiver designed to convert multiple LVDS streams
> +to digital CMOS/TTL parallel data.

You say multiple streams, but bindings describe only one stream.
> +
> +Required properties:
> +- compatible: Shall be one of the following:
> +  "thine,thc63lvd1024",
> +  "lvds-decoder"
> +
> +Optional properties:
> +- supply-vcc: Power supply for TTL output and digital circuitry
> +- supply-cvcc: Power supply for TTL CLOCKOUT signal
> +- supply-lvcc: Power supply for LVDS inputs
> +- supply-pvcc: Power supply for PLL circuitry
> +- pwnd-gpio: Power down GPIO signal. Active low.

Specs [1] uses "/PDWN" name for the pin, moreover gpios suffix is preferred.

Another issue I see is two possibly contradicting conventions:
1. Properties should be named according to specs - so here it should be
named pdwn-gpios.
2. The bindings tries to be generic for lvds decoders, in such case
probably preferred name should be more generic, maybe power-gpios.

Personally I would prefer 1, in such case generic lvds-decoder driver
should look for gpio names according to compatible string.

[1]: http://www.thine.co.jp/files/topics/179_ext_12_0.pdf

> +- oe-gpio: Output enable GPIO signal. Active high.

oe-gpios

> +
> +The THC63LVD1024 has two video ports, whose connections are modeled according
> +to OF graph bindings specified by Documentation/devicetree/bindings/graph.txt
> +
> +- Port@0: LVDS input port
> +- Port@1: Digital CMOS/TTL parallel output

According to specs it has two lvds input and two parallel output ports,
maybe it would be good to describe all here.

Regards
Andrzej

> +
> +Example:
> +-------
> +
> +	lvds_decoder: decoder-0 {
> +		compatible = "thine,thc63lvd1024";
> +
> +		vcc-supply = <&reg_lvds_vcc>;
> +		lvcc-supply = <&reg_lvds_lvcc>;
> +
> +		pwdn-gpio = <&gpio4 15 GPIO_ACTIVE_LOW>;
> +
> +		ports {
> +			#address-cells = <1>;
> +			#size-cells = <0>;
> +
> +			port@0 {
> +				reg = <0>;
> +
> +				lvds_dec_in: endpoint {
> +					remote-endpoint = <&lvds_out>;
> +				};
> +			};
> +
> +			port@1{
> +				reg = <1>;
> +
> +				lvds_dec_out: endpoint {
> +					remote-endpoint = <&adv7511_in>;
> +				};
> +
> +			};
> +
> +		};
> +	};