Re: [RFC 1/2] dt-bindings: usb: dwc3: Add support for multiport related properties

From: Bjorn Andersson <bjorn.andersson@linaro.org>
To: Harsh Agarwal <quic_harshq@quicinc.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Felipe Balbi <balbi@kernel.org>,
	linux-usb@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, quic_pkondeti@quicinc.com,
	quic_ppratap@quicinc.com
Subject: Re: [RFC 1/2] dt-bindings: usb: dwc3: Add support for multiport related properties
Date: Fri, 20 May 2022 20:05:33 -0700	[thread overview]
Message-ID: <YohW/W3Mk0J0AKVt@ripper> (raw)
In-Reply-To: <1652963695-10109-2-git-send-email-quic_harshq@quicinc.com>

On Thu 19 May 05:34 PDT 2022, Harsh Agarwal wrote:

> Added support for multiport, mport, num-ssphy and num-hsphy
> properties. These properties are used to support devices having
> a multiport controller.
> 
> Signed-off-by: Harsh Agarwal <quic_harshq@quicinc.com>

Please do run dt_binding_check on your bindings, even though they are
RFCs.

> ---
>  .../devicetree/bindings/usb/snps,dwc3.yaml         | 55 ++++++++++++++++++++++
>  1 file changed, 55 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/usb/snps,dwc3.yaml b/Documentation/devicetree/bindings/usb/snps,dwc3.yaml
> index f4471f8..39c61483 100644
> --- a/Documentation/devicetree/bindings/usb/snps,dwc3.yaml
> +++ b/Documentation/devicetree/bindings/usb/snps,dwc3.yaml
> @@ -341,6 +341,35 @@ properties:
>        This port is used with the 'usb-role-switch' property  to connect the
>        dwc3 to type C connector.
>  
> +  multiport:

Why are you inventing an of_graph lookalike here?

> +    description:
> +      If a single USB controller supports multiple ports, then it's referred to as
> +      a multiport controller. Each port of the multiport controller can support
> +      either High Speed or Super Speed or both and have their own PHY phandles. Each
> +      port is represented by "mport" node and all the "mport" nodes are grouped
> +      together inside the "multiport" node where individual "mport" node defines the
> +      PHYs supported by that port.
> +    required:
> +      - mport
> +
> +  num-hsphy:
> +    description: Total number of HS-PHYs defined by the multiport controller.
> +    $ref: /schemas/types.yaml#/definitions/uint32

I'm expecting that you wont' have any superspeed-only ports. As such
this number would imply be the number of ports listed under the node.

> +
> +  num-ssphy:
> +    description: Total number of SS-PHYs defined by the multiport controller.
> +    $ref: /schemas/types.yaml#/definitions/uint32

Can you please explain why it's necessary to specify usb_nop_phy?
Wouldn't it be possible to omit the phy in the case of a HS-only port?
In which case this could just be calculated as well.

Regards,
Bjorn

> +
> +  mport:
> +    description: Each mport node represents one port of the multiport controller.
> +    patternProperties: "^mport@[0-9a-f]+$"
> +    oneOf:
> +       - required:
> +         - usb-phy
> +       - required:
> +          - phys
> +          - phy-names
> +
>  unevaluatedProperties: false
>  
>  required:
> @@ -369,4 +398,30 @@ examples:
>        snps,dis_u2_susphy_quirk;
>        snps,dis_enblslpm_quirk;
>      };
> +  - |
> +    usb@4a000000 {
> +      compatible = "snps,dwc3";
> +      reg = <0x4a000000 0xcfff>;
> +      interrupts = <0 92 4>;
> +
> +      multiport {
> +
> +	MP_1: mport@1 {
> +          usb-phy = <&usb2_phy0>, <&usb3_phy0>;
> +	};
> +
> +	MP_2: mport@2 {
> +          usb-phy = <&usb2_phy1>, <&usb3_phy1>;
> +	};
> +
> +	MP_3: mport@3 {
> +          usb-phy = <&usb2_phy2>, <&usb_nop_phy>;
> +	};
> +
> +	MP_4: mport@4 {
> +          usb-phy = <&usb2_phy3>, <&usb_nop_phy>;
> +	};
> +
> +      };
> +    };
>  ...
> -- 
> 2.7.4
> 