Message-ID: <20260206145544.GA207233-robh@kernel.org>
Date: Fri, 6 Feb 2026 08:55:44 -0600
From: Rob Herring <robh@...nel.org>
To: Elson Serrao <elson.serrao@....qualcomm.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konradybcio@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Souradeep Chowdhury <quic_schowdhu@...cinc.com>,
	linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/9] dt-bindings: soc: qcom: eud: Restructure to model
 multi-path hardware

On Mon, Jan 26, 2026 at 03:38:22PM -0800, Elson Serrao wrote:
> The Qualcomm Embedded USB Debugger (EUD) can intercept one or two
> independent High-Speed UTMI paths, depending on the SoC. Each path is
> distinct with its own HS-PHY interface, connector/controller wiring, and
> UTMI routing behavior. The EUD hardware sits between the USB2 PHY and
> the USB controller on each path.
> 
> The existing binding models only a single UTMI path and does not provide
> a way to associate the required High-Speed USB PHY. EUD relies on the
> HS-PHY on the selected UTMI path for link signalling and correct operation
> of the hardware.
> 
> Historically, EUD has worked on platforms that use a single UTMI path
> because the USB controller maintains ownership of the PHY during
> enumeration and normal operation. This implicit relationship allowed
> EUD to function even though the dependency on the PHY was not described
> in the binding. However, this behavior is not guaranteed by hardware.
> The current binding description is not sufficient for SoCs that expose
> two independent UTMI paths, where the PHY association and port wiring
> must be explicitly described.
> 
> Introduce per-path eud-path child nodes so each UTMI path can describe
> its HS-PHY, port connections, and the role‑switching capability of its
> associated USB port.
> 
> Signed-off-by: Elson Serrao <elson.serrao@....qualcomm.com>
> ---
>  .../bindings/soc/qcom/qcom,eud.yaml           | 100 +++++++++++++-----
>  1 file changed, 74 insertions(+), 26 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/soc/qcom/qcom,eud.yaml b/Documentation/devicetree/bindings/soc/qcom/qcom,eud.yaml
> index 84218636c0d8..0507252dbf27 100644
> --- a/Documentation/devicetree/bindings/soc/qcom/qcom,eud.yaml
> +++ b/Documentation/devicetree/bindings/soc/qcom/qcom,eud.yaml
> @@ -10,8 +10,11 @@ maintainers:
>    - Souradeep Chowdhury <quic_schowdhu@...cinc.com>
>  
>  description:
> -  This binding is used to describe the Qualcomm Embedded USB Debugger, which is
> -  mini USB-hub implemented on chip to support USB-based debug capabilities.
> +  This binding describes the Qualcomm Embedded USB Debugger (EUD), an on-chip
> +  mini USB hub that enables USB-based debug capabilities. The EUD block is
> +  positioned between the High-Speed USB PHY and the USB controller, where it
> +  intercepts the UTMI interface to support debug and bypass modes. EUD can be
> +  supported on up to two High-Speed USB ports.
>  
>  properties:
>    compatible:
> @@ -29,26 +32,62 @@ properties:
>      description: EUD interrupt
>      maxItems: 1
>  
> -  ports:
> -    $ref: /schemas/graph.yaml#/properties/ports

You are breaking existing users.

> +  '#address-cells':
> +    const: 1
> +
> +  '#size-cells':
> +    const: 0
> +
> +patternProperties:
> +  "^eud-path@[0-1]$":
> +    type: object
>      description:
> -      These ports is to be attached to the endpoint of the DWC3 controller node
> -      and type C connector node. The controller has the "usb-role-switch"
> -      property.
> +      Represents one High-Speed UTMI path that EUD intercepts. This node models
> +      the physical data path intercepted by EUD and provides graph endpoints to
> +      link the USB controller and the external connector associated with this path.
>  
>      properties:
> -      port@0:
> -        $ref: /schemas/graph.yaml#/properties/port
> -        description: This port is to be attached to the DWC3 controller.
> +      reg:
> +        maxItems: 1
> +        description: Path number
> +
> +      phys:
> +        maxItems: 1
> +        description: High-Speed USB PHY associated with this data path.

Doesn't the DWC3 node have a phys property? You don't need it twice 
since you can walk the graph.

> +
> +      usb-role-switch:
> +        type: boolean
> +        description:
> +          Set this property if the USB port on this path is role switch capable.
> +          In device role, debug mode inserts the EUD hub into the UTMI path. In
> +          host role, the EUD hub is bypassed and UTMI traffic flows directly
> +          between the PHY and the USB controller.
> +
> +      ports:
> +        $ref: /schemas/graph.yaml#/properties/ports
> +        description:
> +          These ports are to be attached to the endpoint of the USB controller node
> +          and USB connector node.
> +
> +        properties:
> +          port@0:
> +            $ref: /schemas/graph.yaml#/properties/port
> +            description: This port is to be attached to the USB controller.
>  
> -      port@1:
> -        $ref: /schemas/graph.yaml#/properties/port
> -        description: This port is to be attached to the type C connector.
> +          port@1:
> +            $ref: /schemas/graph.yaml#/properties/port
> +            description: This port is to be attached to the USB connector.

Both port 0 and 1 are attached to the USB controller?

Why can't you just add more port nodes to the existing binding?

Rob

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