linux-kernel - Re: [PATCH] dt-bindings: usb: Add binding for Microchip usb5744 hub controller

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Message-ID: <4aa7adbf-f89e-6819-64d2-5942a456528a@linaro.org>
Date:   Thu, 4 May 2023 08:46:45 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Michal Simek <michal.simek@....com>, linux-kernel@...r.kernel.org,
        monstr@...str.eu, michal.simek@...inx.com, git@...inx.com,
        ilias.apalodimas@...aro.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Piyush Mehta <piyush.mehta@....com>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-usb@...r.kernel.org
Subject: Re: [PATCH] dt-bindings: usb: Add binding for Microchip usb5744 hub
 controller

On 03/05/2023 15:39, Michal Simek wrote:
> The Microchip usb5744 is a SS/HS USB 3.0 hub controller with 4 ports.
> The binding describes USB related aspects of the USB5744 hub, it as
> well cover the option of connecting the controller as an i2c slave.
> When i2c interface is connected hub needs to be initialized first.
> Hub itself has fixed i2c address 0x2D but hardcoding address is not good
> idea because address can be shifted by i2c address translator in the
> middle.
> 
> Signed-off-by: Piyush Mehta <piyush.mehta@....com>
> Signed-off-by: Michal Simek <michal.simek@....com>
> ---
> 
> It looks like that usb8041 has also an optional i2c interface which is not
> covered. But it is mentioned at commit 40e58a8a7ca6 ("dt-bindings: usb:
> Add binding for TI USB8041 hub controller").
> 
> i2c-bus name property was suggested by Rob at
> https://lore.kernel.org/all/CAL_JsqJedhX6typpUKbnzV7CLK6UZVjq3CyG9iY_j5DLPqvVdw@mail.gmail.com/
> and
> https://lore.kernel.org/all/CAL_JsqJZBbu+UXqUNdZwg-uv0PAsNg55026PTwhKr5wQtxCjVQ@mail.gmail.com/
> 
> the question is if adding address like this is acceptable.
> But it must be specified.

Why? phandle points it explicitly.

> 
> Driver will follow based on final dt-binding.
> 
> ---
>  .../bindings/usb/microchip,usb5744.yaml       | 85 +++++++++++++++++++
>  1 file changed, 85 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/usb/microchip,usb5744.yaml
> 
> diff --git a/Documentation/devicetree/bindings/usb/microchip,usb5744.yaml b/Documentation/devicetree/bindings/usb/microchip,usb5744.yaml
> new file mode 100644
> index 000000000000..fafe275a35df
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/usb/microchip,usb5744.yaml
> @@ -0,0 +1,85 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/usb/microchip,usb5744.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Microchip USB5744 4-port Hub Controller
> +
> +description:
> +  Microchip's USB5744 SmartHubTM IC is a 4 port, SuperSpeed (SS)/Hi-Speed (HS),
> +  low power, low pin count configurable and fully compliant with the USB 3.1
> +  Gen 1 specification. The USB5744 also supports Full Speed (FS) and Low Speed
> +  (LS) USB signaling, offering complete coverage of all defined USB operating
> +  speeds. The new SuperSpeed hubs operate in parallel with the USB 2.0
> +  controller, so 5 Gbps SuperSpeed data transfers are not affected by slower
> +  USB 2.0 traffic.
> +
> +maintainers:
> +  - Piyush Mehta <piyush.mehta@....com>
> +  - Michal Simek <michal.simek@....com>
> +
> +allOf:
> +  - $ref: usb-device.yaml#
> +
> +properties:
> +  compatible:
> +    enum:
> +      - usb424,5744
> +      - usb424,2744

Keep the list ordered, so 2744 before 5744.

> +
> +  reg: true
> +
> +  reset-gpios:
> +    maxItems: 1
> +    description:
> +      GPIO controlling the GRST# pin.
> +
> +  vdd-supply:
> +    description:
> +      VDD power supply to the hub
> +
> +  peer-hub:
> +    $ref: /schemas/types.yaml#/definitions/phandle
> +    description:
> +      phandle to the peer hub on the controller.
> +
> +  i2c-bus:
> +    maxItems: 1
> +    description:
> +      phandle of an I2C controller to link usb-hub for usb attach and reset
> +      followed by i2c address.
> +
> +required:
> +  - compatible
> +  - reg
> +  - peer-hub
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/gpio/gpio.h>
> +
> +    usb {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        /* 2.0 hub on port 1 */
> +        hub_2_0: hub@1 {
> +          compatible = "usb424,5744";

Mixed indentation, use four spaces here as well.

> +          reg = <1>;
> +          peer-hub = <&hub_3_0>;
> +          i2c-bus = <&i2c 0x2d>;
> +          reset-gpios = <&gpio 3 GPIO_ACTIVE_LOW>;
> +        };
Krzysztof