Re: [PATCH v4 1/2] dt-bindings: usb: cdns3: Add no_drd property

[Conor Dooley <conor@kernel.org>]

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On Tue, May 12, 2026 at 01:44:24PM +0200, Pawel Laszczak via B4 Relay wrote:
> From: Pawel Laszczak <pawell@cadence.com>
> 
> Introduce a new boolean property 'no_drd' for Cadence USBSS/USBSSP
> controllers.
> 
> Some hardware configurations of this controller are designed without
> the Dual-Role Device (DRD) register block or have it inaccessible.
> In such cases, the driver must skip all OTG/DRD register accesses
> to avoid bus errors and cannot rely on hardware-based role switching.
> 
> To accommodate these configurations, also relax the requirements for
> the 'reg' and 'interrupts' properties, making the 'otg' resources
> optional.

Why unconditionally? I think these hardware configurations need
device-specific compatibles and the constraints lowered on a
case-by-case basis.

Probably those compatibles should require no_drd too.

Alternatively to doing the conditions per compatible, if no_drd is
present, maxItems for these properties should be set to 2, and when
absent minItems set to 3.

pw-bot: changes-requested

Thanks,
Conor.

> 
> Signed-off-by: Pawel Laszczak <pawell@cadence.com>
> ---
>  Documentation/devicetree/bindings/usb/cdns,usb3.yaml | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/usb/cdns,usb3.yaml b/Documentation/devicetree/bindings/usb/cdns,usb3.yaml
> index 2d95fb7321af..8c7dc81708fb 100644
> --- a/Documentation/devicetree/bindings/usb/cdns,usb3.yaml
> +++ b/Documentation/devicetree/bindings/usb/cdns,usb3.yaml
> @@ -20,19 +20,21 @@ properties:
>      const: cdns,usb3
>  
>    reg:
> +    minItems: 2
>      items:
>        - description: OTG controller registers
>        - description: XHCI Host controller registers
>        - description: DEVICE controller registers
>  
>    reg-names:
> +    minItems: 2
>      items:
>        - const: otg
>        - const: xhci
>        - const: dev
>  
>    interrupts:
> -    minItems: 3
> +    minItems: 2
>      items:
>        - description: XHCI host controller interrupt
>        - description: Device controller interrupt
> @@ -41,7 +43,7 @@ properties:
>                       cleared by xhci core, this interrupt is optional
>  
>    interrupt-names:
> -    minItems: 3
> +    minItems: 2
>      items:
>        - const: host
>        - const: peripheral
> @@ -79,6 +81,13 @@ properties:
>      description: Enable resetting of PHY if Rx fail is detected
>      type: boolean
>  
> +  no_drd:
> +    description:
> +      Indicates that the Dual-Role Device (DRD) register block is not
> +      implemented or is inaccessible. In this case, the controller
> +      must operate in a fixed peripheral or host mode.
> +    type: boolean
> +
>  dependencies:
>    port: [ usb-role-switch ]
>  
> 
> -- 
> 2.43.0
> 
> 

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