linux-kernel - Re: [RFC PATCH 1/3] dt-binding: usb: ulpi-phy: add ulpi-phy binding

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Message-ID: <20230929-harmonics-chapter-54f1819383fa@spud>
Date:   Fri, 29 Sep 2023 15:04:28 +0100
From:   Conor Dooley <conor@...nel.org>
To:     Piyush Mehta <piyush.mehta@....com>
Cc:     gregkh@...uxfoundation.org, michal.simek@....com,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        conor+dt@...nel.org, peter.chen@...nel.org,
        linus.walleij@...aro.org, paul@...pouillou.net, arnd@...db.de,
        linux-usb@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, git@....com
Subject: Re: [RFC PATCH 1/3] dt-binding: usb: ulpi-phy: add ulpi-phy binding

Hey,

On Fri, Sep 29, 2023 at 12:18:50PM +0530, Piyush Mehta wrote:
> Create an ulpi-phy binding to read and write PHY registers with explicit
> control of the address and data using the usb.VIEWPORT register.
> 
> Signed-off-by: Piyush Mehta <piyush.mehta@....com>
> ---
> This binding patch was created to support generic platforms. This binding
> will be modified in accordance with patch [3/3] procedures. One of the
> approch may be Create a zynq phy platform driver in "driver/usb/phy" with
> driver source "phy-ulpi-zynq-usb.c" and then the binding will be particular
> to the Xilinx/AMD zynq platform.

I don't understand what the drivers have to do with describing the
hardware here. You have a zynq platform with this phy, so the compatible
should reflect that. Whether you create some software that supports
generic platforms is mostly a separate question IMO.

> This binding was built with the Zynq hardware design example in consideration
> of as a generic platform. The viewport provide access the Chipidea controller
> to interface with the ULPI PHY.
> ---
>  .../devicetree/bindings/usb/ulpi-phy.yaml     | 48 +++++++++++++++++++
>  1 file changed, 48 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/usb/ulpi-phy.yaml
> 
> diff --git a/Documentation/devicetree/bindings/usb/ulpi-phy.yaml b/Documentation/devicetree/bindings/usb/ulpi-phy.yaml
> new file mode 100644
> index 000000000000..490b2f610129
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/usb/ulpi-phy.yaml
> @@ -0,0 +1,48 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/usb/ulpi-phy.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: ULPI PHY- Generic platform
> +
> +maintainers:
> +  - Piyush Mehta <piyush.mehta@....com>
> +
> +properties:
> +  compatible:
> +    const: ulpi-phy

Please add a device specific compatible here.

> +
> +  reg:
> +    maxItems: 1
> +
> +  '#phy-cells':
> +    const: 0
> +
> +  external-drv-vbus:
> +    description:
> +      If present, configure ulpi-phy external supply to drive 5V on VBus.
> +    type: boolean
> +
> +  view-port:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description:
> +      Address to read and write PHY registers with explicit control of
> +      the address and data using the usb.VIEWPORT register.

Why would this not just be a second entry in reg?

Cheers,
Conor.

> +
> +required:
> +  - compatible
> +  - reg
> +  - view-port
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    phy0@...02000 {
> +        compatible = "ulpi-phy";
> +        #phy-cells = <0x00>;
> +        reg = <0xe0002000 0x1000>;
> +        view-port = <0x170>;
> +        external-drv-vbus;
> +    };
> -- 
> 2.17.1
> 

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