linux-kernel - Re: [PATCH 1/2] dt-bindings: it6251: add bindings for IT6251 LVDS-to-eDP bridge

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Message-ID: <20200509134410.GA5946@pendragon.ideasonboard.com>
Date:   Sat, 9 May 2020 16:44:10 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     srk@...io
Cc:     Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Lubomir Rintel <lkundrak@...sk>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Marek Vasut <marex@...x.de>,
        Sean Cross <xobs@...agi.com>
Subject: Re: [PATCH 1/2] dt-bindings: it6251: add bindings for IT6251
 LVDS-to-eDP bridge

Hi Richard,

Thank you for the patch.

On Sat, May 09, 2020 at 01:17:31PM +0200, srk@...io wrote:
> From: Marek Vasut <marex@...x.de>
> 
> Add DT bindings for ITE IT6251 LVDS-to-eDP bridge.
> 
> Signed-off-by: Marek Vasut <marex@...x.de>
> Signed-off-by: Richard Marko <srk@...io>
> Cc: Daniel Vetter <daniel@...ll.ch>
> Cc: Rob Herring <robh+dt@...nel.org>
> Cc: Sean Cross <xobs@...agi.com>
> Cc: devicetree@...r.kernel.org
> To: dri-devel@...ts.freedesktop.org
> ---
>  .../bindings/display/bridge/ite,it6251.yaml   | 97 +++++++++++++++++++
>  1 file changed, 97 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/display/bridge/ite,it6251.yaml
> 
> diff --git a/Documentation/devicetree/bindings/display/bridge/ite,it6251.yaml b/Documentation/devicetree/bindings/display/bridge/ite,it6251.yaml
> new file mode 100644
> index 000000000000..8daa44a30fa1
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/bridge/ite,it6251.yaml
> @@ -0,0 +1,97 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/display/bridge/ite,it6251.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: ITE IT6251 LVDS-to-eDP bridge bindings
> +
> +maintainers:
> +  - Marek Vasut <marex@...x.de>
> +  - Richard Marko <srk@...io>
> +
> +description: |
> +  The IT6251 is a high-performance single-chip
> +  De-SSC LVDS to DisplayPort converter.
> +  Combined with LVDS receiver and DisplayPort Transmitter,
> +  the IT6251 supports LVDS input and DisplayPort 1.1a
> +  output by conversion function.

You could reflow this to the 80 columns limit. It also sounds like
marketing material copied from the datasheet, with "by conversion
function" likely a bad translation.

> +
> +properties:
> +  compatible:
> +    const: ite,it6251
> +
> +  reg:
> +    items:
> +      - description: I2C address of the bridge
> +      - description: I2C address of the LVDS part
> +
> +  reg-names:
> +    items:
> +      - const: bridge
> +      - const: lvds
> +
> +  ports:
> +    type: object
> +
> +    properties:
> +      "#address-cells":
> +        const: 1
> +
> +      "#size-cells":
> +        const: 0
> +
> +      port@0:
> +        type: object
> +        description: |
> +         Video port for eDP output (typically panel).
> +
> +      port@1:
> +        type: object
> +        description: |
> +          Video port for LVDS input.

We traditionally use port 0 for the input and port 1 for the output. I'd
rather do the same here to remain consistent, and allow generic code to
operate on this device.

> +
> +    required:
> +      - port@0
> +      - port@1
> +
> +    additionalProperties: false
> +
> +  power-supply: true

There are multiple power supplies for the chip, shouldn't we have
multiple properties ? I would also name the properties according to the
supply name.

The chip has an HPD input. I would recommend already documenting an
optional boolean no-hpd property to report when the HPD input is not
connected.

> +
> +required:
> +  - compatible
> +  - reg
> +  - reg-names
> +  - power-supply
> +  - ports
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    it6251@5c {
> +      compatible = "ite,it6251";
> +      reg = <0x5c>, <0x5e>;
> +      reg-names = "bridge", "lvds";
> +      power-supply = <&reg_display>;
> +
> +      ports {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        port@0 {
> +          reg = <0>;
> +          bridge_out_edp0: endpoint {
> +            remote-endpoint = <&panel_in_edp0>;
> +          };
> +        };
> +
> +        port@1 {
> +          reg = <1>;
> +          bridge_in_lvds0: endpoint {
> +            remote-endpoint = <&lvds0_out>;
> +          };
> +        };
> +      };
> +    };

-- 
Regards,

Laurent Pinchart