Re: [PATCH 5/7] dt-bindings: usb: google,cros-ec-typec: Add ports for DP altmode

[Rob Herring <robh@kernel.org>]

On Tue, Apr 15, 2025 at 05:02:05PM -0700, Stephen Boyd wrote:
> Add a DT graph binding to google,cros-ec-typec so that it can combine
> DisplayPort (DP) and USB SuperSpeed (SS) data into a USB type-c endpoint
> that is connected to the usb-c-connector node's SS endpoint. Allow there
> to be multiple 'typec' nodes underneath the EC node so that one DT graph
> exists per DP bridge. The EC is actually controlling TCPCs and redrivers
> that combine the DP and USB signals together so this more accurately
> reflects the hardware design without introducing yet another DT node
> underneath the EC for USB type-c "stuff".
> 
> If the type-c ports are being shared between a single DP controller then
> the ports need to know about each other and determine a policy to drive
> DP to one type-c port or the other. If the type-c ports each have their
> own dedicated DP controller then they're able to operate independently
> and enter/exit DP altmode independently as well. We can't connect the DP
> controller's endpoint to one usb-c-connector port@1 endpoint and the USB
> controller's endpoint to another usb-c-connector port@1 endpoint either
> because the DP muxing case would have DP connected to two
> usb-c-connector endpoints which the graph binding doesn't support.
> 
> Therefore, one typec node is required per the capabilities of the type-c
> port(s) being managed. Add a port to the DisplayPort altmode as well, so
> that we can show the connection between the DP controller and the DP
> altmode. This lets us indicate which type-c ports the DP controller is
> wired to. For example, if DP was connected to ports 0 and 2, while port
> 1 was connected to another DP controller we wouldn't be able to
> implement that without having some other DT property to indicate which
> output ports are connected to the DP endpoint.
> 
> Furthermore, this supports ChromeOS designs like Corsola where a DP
> controller/PHY is split with two lanes going to one connector and the
> other two lanes going to another connector. In this case, we wouldn't
> have the graph binding under the cros-ec-typec node, but we would have
> the graph binding in the DP altmode directly connected to the DP
> controller's two output endpoints.
> 
> Cc: Rob Herring (Arm) <robh@kernel.org>
> Cc: Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>
> Cc: Conor Dooley <conor+dt@kernel.org>
> Acked-by: Lee Jones <lee@kernel.org>
> Cc: Benson Leung <bleung@chromium.org>
> Cc: Guenter Roeck <groeck@chromium.org>
> Cc: Tzung-Bi Shih <tzungbi@kernel.org>
> Cc: <devicetree@vger.kernel.org>
> Cc: <chrome-platform@lists.linux.dev>
> Cc: Pin-yen Lin <treapking@chromium.org>
> Cc: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
> Cc: Łukasz Bartosik <ukaszb@chromium.org>
> Cc: Jameson Thies <jthies@google.com>
> Cc: Andrei Kuchynski <akuchynski@chromium.org>
> Signed-off-by: Stephen Boyd <swboyd@chromium.org>
> ---
>  .../bindings/connector/usb-connector.yaml     |   6 +
>  .../bindings/mfd/google,cros-ec.yaml          |   7 +-
>  .../bindings/usb/google,cros-ec-typec.yaml    | 165 ++++++++++++++++++
>  3 files changed, 175 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/connector/usb-connector.yaml b/Documentation/devicetree/bindings/connector/usb-connector.yaml
> index 11e40d225b9f..e3d60997c03e 100644
> --- a/Documentation/devicetree/bindings/connector/usb-connector.yaml
> +++ b/Documentation/devicetree/bindings/connector/usb-connector.yaml
> @@ -179,6 +179,12 @@ properties:
>              $ref: /schemas/types.yaml#/definitions/uint32
>              description: VDO returned by Discover Modes USB PD command.
>  
> +          port:
> +            $ref: /schemas/graph.yaml#/properties/port
> +            description: OF graph bindings modeling a data bus to the
> +              DisplayPort altmode from the DisplayPort controller. Used when
> +              the altmode switch is part of the port manager.
> +

Why can't this connection be another endpoint on port@1 as that is the 
port for the SS signals.

>    port:
>      $ref: /schemas/graph.yaml#/properties/port
>      description: OF graph bindings modeling a data bus to the connector, e.g.
> diff --git a/Documentation/devicetree/bindings/mfd/google,cros-ec.yaml b/Documentation/devicetree/bindings/mfd/google,cros-ec.yaml
> index ac89696fa649..63d506e88abb 100644
> --- a/Documentation/devicetree/bindings/mfd/google,cros-ec.yaml
> +++ b/Documentation/devicetree/bindings/mfd/google,cros-ec.yaml
> @@ -98,9 +98,6 @@ properties:
>  
>    gpio-controller: true
>  
> -  typec:
> -    $ref: /schemas/usb/google,cros-ec-typec.yaml#
> -
>    ec-pwm:
>      $ref: /schemas/pwm/google,cros-ec-pwm.yaml#
>      deprecated: true
> @@ -163,6 +160,10 @@ patternProperties:
>      type: object
>      $ref: /schemas/extcon/extcon-usbc-cros-ec.yaml#
>  
> +  "^typec(-[0-9])*$":
> +    type: object
> +    $ref: /schemas/usb/google,cros-ec-typec.yaml#
> +
>  required:
>    - compatible
>  
> diff --git a/Documentation/devicetree/bindings/usb/google,cros-ec-typec.yaml b/Documentation/devicetree/bindings/usb/google,cros-ec-typec.yaml
> index 3272d0e01f7e..611345bbe884 100644
> --- a/Documentation/devicetree/bindings/usb/google,cros-ec-typec.yaml
> +++ b/Documentation/devicetree/bindings/usb/google,cros-ec-typec.yaml
> @@ -26,6 +26,55 @@ properties:
>    '#size-cells':
>      const: 0
>  
> +  mux-gpios:
> +    description: GPIOs indicating which way the DisplayPort mux is steered
> +    minItems: 1
> +    maxItems: 3
> +
> +  no-hpd:
> +    description: Indicates this device doesn't signal HPD for DisplayPort
> +    type: boolean
> +
> +  ports:
> +    $ref: /schemas/graph.yaml#/properties/ports
> +
> +    properties:
> +      port@0:
> +        $ref: /schemas/graph.yaml#/properties/port
> +        description:
> +          Port for DisplayPort (DP) data
> +
> +        properties:
> +          endpoint@0:
> +            $ref: /schemas/graph.yaml#/properties/endpoint
> +            description: Input DP port
> +
> +        patternProperties:
> +          '^endpoint@[1-8]$':
> +            $ref: /schemas/graph.yaml#/properties/endpoint
> +            description: Output to the usb-c connector's DP altmode

This is odd. Generally (or always?) a port is 1 direction.

Other bindings IIRC have 3 ports in the device doing the muxing: 1 
output for connector port@1, 1 USB SS input, and 1 DP input.

Rob