Re: [PATCH v8 1/2] dt-bindings: usb: cdns3: Add cdns,cdnsp-no-drd compatible string

[Conor Dooley <conor@kernel.org>]

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On Fri, May 15, 2026 at 01:24:38PM +0200, Pawel Laszczak via B4 Relay wrote:
> From: Pawel Laszczak <pawell@cadence.com>
> 
> Introduce a new compatible string 'cdns,cdnsp-no-drd' for Cadence
> USBSS/USBSSP controllers to support hardware configurations where the
> Dual-Role Device (DRD) register block is missing or inaccessible.
> 
> This change follows the recommendation to imply hardware limitations
> directly from the compatible string rather than using a dedicated
> boolean property.
> 
> When 'cdns,cdnsp-no-drd' is used:
> - The 'otg' register and interrupt resources are not required.
> - The 'reg' and 'interrupts' properties are restricted to 2 items
>   (host and device).
> - 'dr_mode' must be explicitly set to either 'host' or 'peripheral'.
> 
> The standard 'cdns,usb3' compatible remains unchanged, maintaining
> backward compatibility by requiring all 3 resource sets (otg, host, dev).
> 
> Signed-off-by: Pawel Laszczak <pawell@cadence.com>
> ---
> v8:
> - Update commit message to reflect schema changes.
> - Removed 'cdns,no-drd' boolean property as per Rob Herring's suggestion.
> - Introduced a new compatible string 'cdns,cdnsp-no-drd' for controller
>   variants that lack the DRD/OTG register block.
> 
> v7:
> - Rename 'no_drd' to 'cdns,no-drd'.
> - Update commit message to reflect property renaming and schema changes.
> - Simplify 'reg-names' using a single enum.
> - Revert 'interrupt-names' to a list of constants.
> - Move 'reg' item descriptions to if/else blocks for accuracy.
> - Clean up 'if/then' logic (remove redundant checks).
> - Add explicit 'items' list for 'interrupt-names' in the 'else' block.
> 
> v6:
> - Fixed validation error for 'interrupt-names' by correcting
>   the items definition.
> - Adjusted 'minItems'/'maxItems' to properly support the optional
>  'wakeup' interrupt.
> - Fixed 'too long' schema error in examples.
> 
> v5:
> - Implemented strict conditional validation using if-then-else logic.
> - Enforced 2 register/interrupt items and required 'dr_mode'
>   (host or peripheral) when 'no_drd' is present.
> - Enforced the standard 3 register/interrupt items (otg, host, dev)
>   when 'no_drd' is absent to ensure backward compatibility.
> - Updated 'reg-names' and 'interrupt-names' to use enums in the main
>   properties section to support flexible resource ordering during
>   validation.
> ---
> ---
>  .../devicetree/bindings/usb/cdns,usb3.yaml         | 60 ++++++++++++++++++----
>  1 file changed, 50 insertions(+), 10 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/usb/cdns,usb3.yaml b/Documentation/devicetree/bindings/usb/cdns,usb3.yaml
> index 2d95fb7321af..7b0aa9c4a2bd 100644
> --- a/Documentation/devicetree/bindings/usb/cdns,usb3.yaml
> +++ b/Documentation/devicetree/bindings/usb/cdns,usb3.yaml
> @@ -17,22 +17,22 @@ description:
>  
>  properties:
>    compatible:
> -    const: cdns,usb3
> +    enum:
> +      - cdns,usb3
> +      - cdns,cdnsp-no-drd

I doubt this is what Rob meant, he asked for soc-specific compatibles
and this is generic. A soc-specific compatible would be something like
microchip,newsoc-usb3

Thanks,
Conor.

>  
>    reg:
> -    items:
> -      - description: OTG controller registers
> -      - description: XHCI Host controller registers
> -      - description: DEVICE controller registers
> +    minItems: 2
> +    maxItems: 3
>  
>    reg-names:
> +    minItems: 2
> +    maxItems: 3
>      items:
> -      - const: otg
> -      - const: xhci
> -      - const: dev
> +      enum: [ otg, xhci, dev ]
>  
>    interrupts:
> -    minItems: 3
> +    minItems: 2
>      items:
>        - description: XHCI host controller interrupt
>        - description: Device controller interrupt
> @@ -41,7 +41,7 @@ properties:
>                       cleared by xhci core, this interrupt is optional
>  
>    interrupt-names:
> -    minItems: 3
> +    minItems: 2
>      items:
>        - const: host
>        - const: peripheral
> @@ -93,6 +93,46 @@ allOf:
>    - $ref: usb-drd.yaml#
>    - $ref: usb-xhci.yaml#
>  
> +  - if:
> +      properties:
> +        compatible:
> +          const: cdns,cdnsp-no-drd
> +    then:
> +      properties:
> +        reg:
> +          items:
> +            - description: XHCI Host controller registers
> +            - description: DEVICE controller registers
> +        reg-names:
> +          items:
> +            - const: xhci
> +            - const: dev
> +        interrupts:
> +          maxItems: 2
> +        interrupt-names:
> +          items:
> +            - const: host
> +            - const: peripheral
> +        dr_mode:
> +          enum: [host, peripheral]
> +    else:
> +      properties:
> +        reg:
> +          items:
> +            - description: OTG controller registers
> +            - description: XHCI Host controller registers
> +            - description: DEVICE controller registers
> +        reg-names:
> +          items:
> +            - const: otg
> +            - const: xhci
> +            - const: dev
> +        interrupts:
> +          minItems: 3
> +          maxItems: 4
> +        interrupt-names:
> +          minItems: 3
> +
>  unevaluatedProperties: false
>  
>  examples:
> 
> -- 
> 2.43.0
> 
> 

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