linux-kernel - Re: [PATCH 07/12] dt-bindings: tc358754: add DT bindings

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Date:   Mon, 28 May 2018 13:18:36 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Maciej Purski <m.purski@...sung.com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, devicetree@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, David Airlie <airlied@...ux.ie>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Thierry Reding <thierry.reding@...il.com>,
        Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Archit Taneja <architt@...eaurora.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Inki Dae <inki.dae@...sung.com>,
        Joonyoung Shim <jy0922.shim@...sung.com>,
        Seung-Woo Kim <sw0312.kim@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH 07/12] dt-bindings: tc358754: add DT bindings

Hi Maciej,

Thank you for the patch.

On Monday, 28 May 2018 12:47:11 EEST Maciej Purski wrote:
> The patch adds bindings to Toshiba DSI/LVDS bridge TC358764.
> Bindings describe power supplies, reset gpio and video interfaces.
> 
> Signed-off-by: Andrzej Hajda <a.hajda@...sung.com>
> Signed-off-by: Maciej Purski <m.purski@...sung.com>
> ---
>  .../bindings/display/bridge/toshiba,tc358764.txt   | 42 +++++++++++++++++++
>  1 file changed, 42 insertions(+)
>  create mode 100644
> Documentation/devicetree/bindings/display/bridge/toshiba,tc358764.txt
> 
> diff --git
> a/Documentation/devicetree/bindings/display/bridge/toshiba,tc358764.txt
> b/Documentation/devicetree/bindings/display/bridge/toshiba,tc358764.txt new
> file mode 100644
> index 0000000..d09bdc2
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/bridge/toshiba,tc358764.txt
> @@ -0,0 +1,42 @@
> +TC358764 MIPI-DSI to LVDS panel bridge
> +
> +Required properties:
> +  - compatible: "toshiba,tc358764"
> +  - reg: the virtual channel number of a DSI peripheral
> +  - vddc-supply: core voltage supply
> +  - vddio-supply: I/O voltage supply
> +  - vddmipi-supply: MIPI voltage supply
> +  - vddlvds133-supply: LVDS1 3.3V voltage supply
> +  - vddlvds112-supply: LVDS1 1.2V voltage supply

That's a lot of power supplies. Could some of them be merged together ? See 
https://patchwork.freedesktop.org/patch/216058/ for an earlier discussion on 
the same subject.

> +  - reset-gpios: a GPIO spec for the reset pin
> +
> +The device node can contain zero to two 'port' child nodes, each with one
> +child
> +'endpoint' node, according to the bindings defined in [1].
> +The following are properties specific to those nodes.
> +
> +port:
> +  - reg: (required) can be 0 for DSI port or 1 for LVDS port;

This seems pretty vague to me. It could be read as meaning that ports are 
completely optional, and that the port number you list can be used, but that 
something else could be used to.

Let's make the port nodes mandatory. I propose the following.

Required nodes:

The TC358764 has DSI and LVDS ports whose connections are described using the 
OF graph bindings defined in Documentation/devicetree/bindings/graph.txt. The 
device node must contain one 'port' child node per DSI and LVDS port. The port 
nodes are numbered as follows.

  Port                  Number
-------------------------------------------------------------------
  DSI Input             0
  LVDS Output           1

Each port node must contain endpoint nodes describing the hardware 
connections.

> +[1]: Documentation/devicetree/bindings/media/video-interfaces.txt
> +
> +Example:
> +
> +	bridge@0 {
> +		reg = <0>;
> +		compatible = "toshiba,tc358764";
> +		vddc-supply = <&vcc_1v2_reg>;
> +		vddio-supply = <&vcc_1v8_reg>;
> +		vddmipi-supply = <&vcc_1v2_reg>;
> +		vddlvds133-supply = <&vcc_3v3_reg>;
> +		vddlvds112-supply = <&vcc_1v2_reg>;
> +		reset-gpios = <&gpd1 6 GPIO_ACTIVE_LOW>;
> +		#address-cells = <1>;
> +		#size-cells = <0>;
> +		port@1 {
> +			reg = <1>;
> +			lvds_ep: endpoint {
> +				remote-endpoint = <&panel_ep>;
> +			};
> +		};
> +	};

-- 
Regards,

Laurent Pinchart