linux-kernel - Re: [PATCH v5 1/9] dt-bindings: usb: Add Type-C switch binding

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Date:   Thu, 23 Jun 2022 14:30:53 -0400
From:   Stephen Boyd <swboyd@...omium.org>
To:     Prashant Malani <pmalani@...omium.org>,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Cc:     bleung@...omium.org, heikki.krogerus@...ux.intel.com,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Nícolas F . R . A . Prado 
        <nfraprado@...labora.com>, Allen Chen <allen.chen@....com.tw>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>, devicetree@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Jonas Karlman <jonas@...boo.se>,
        José Expósito <jose.exposito89@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Maxime Ripard <maxime@...no.tech>,
        Neil Armstrong <narmstrong@...libre.com>,
        Pin-Yen Lin <treapking@...omium.org>,
        Robert Foss <robert.foss@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Sam Ravnborg <sam@...nborg.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Xin Ji <xji@...logixsemi.com>
Subject: Re: [PATCH v5 1/9] dt-bindings: usb: Add Type-C switch binding

Quoting Prashant Malani (2022-06-22 10:34:30)
> diff --git a/Documentation/devicetree/bindings/usb/typec-switch.yaml b/Documentation/devicetree/bindings/usb/typec-switch.yaml
> new file mode 100644
> index 000000000000..78b0190c8543
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/usb/typec-switch.yaml
> @@ -0,0 +1,74 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/usb/typec-switch.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: USB Type-C Switch
> +
> +maintainers:
> +  - Prashant Malani <pmalani@...omium.org>
> +
> +description:
> +  A USB Type-C switch represents a component which routes USB Type-C data
> +  lines to various protocol host controllers (e.g USB, VESA DisplayPort,
> +  Thunderbolt etc.) depending on which mode the Type-C port, port partner
> +  and cable are operating in. It can also modify lane routing based on
> +  the orientation of a connected Type-C peripheral.
> +
> +properties:
> +  compatible:
> +    const: typec-switch
> +
> +  mode-switch:
> +    type: boolean
> +    description: Specify that this switch can handle alternate mode switching.
> +
> +  orientation-switch:
> +    type: boolean
> +    description: Specify that this switch can handle orientation switching.
> +
> +  ports:
> +    $ref: /schemas/graph.yaml#/properties/ports
> +    description: OF graph binding modelling data lines to the Type-C switch.
> +
> +    properties:
> +      port@0:
> +        $ref: /schemas/graph.yaml#/properties/port
> +        description: Link between the switch and a Type-C connector.

Is there an update to the usb-c-connector binding to accept this port
connection?

> +
> +    required:
> +      - port@0
> +
> +required:
> +  - compatible
> +  - ports
> +
> +anyOf:
> +  - required:
> +      - mode-switch
> +  - required:
> +      - orientation-switch
> +
> +additionalProperties: true
> +
> +examples:
> +  - |
> +    drm-bridge {
> +        usb-switch {
> +            compatible = "typec-switch";

I still don't understand the subnode design here. usb-switch as a
container node indicates to me that this is a bus, but in earlier rounds
of this series it was stated this isn't a bus. Why doesn't it work to
merge everything inside usb-switch directly into the drm-bridge node?

> +            mode-switch;
> +            orientation-switch;
> +            ports {
> +                #address-cells = <1>;
> +                #size-cells = <0>;
> +
> +                port@0 {
> +                    reg = <0>;
> +                    anx_ep: endpoint {
> +                        remote-endpoint = <&typec_controller>;
> +                    };
> +                };
> +            };
> +        };