Re: [PATCH 1/3] dt-bindings: usb: Add binding for TI USB8041 hub controller

[Matthias Kaehlcke <mka@chromium.org>]

Hi Alexander,

On Tue, Jul 12, 2022 at 05:06:25PM +0200, Alexander Stein wrote:
> The TI USB8041 is a USB 3.0 hub controller with 4 ports.
> 
> This initial version of the binding only describes USB related aspects
> of the USB8041, it does not cover the option of connecting the controller
> as an i2c slave.
> 
> Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
> ---
> Well, this is essentially a ripoff of
> Documentation/devicetree/bindings/usb/realtek,rts5411.yaml with USB IDs
> replaced, reset-gpio added and example adjusted.
> IMHO this should be merged together with realtek,rts5411.yaml. Is it ok
> to rename bindings files? I guess a common onboard-usb-hub.yaml matching
> the driver seens reasonable. Any recommendations how to proceed?

It's a tradeoff between keeping the individual bindings simple and avoid
unnecessary duplication. The current RTS5411 and TI USB8041 bindings are
very similar, which suggests combining them. However over time hubs with
diverging features could be added (e.g. with multiple regulators, a link
to an I2C/SPI bus, a clock, ...). With that a common binding might become
too messy.

From a quick look through Documentation/devicetree/bindings it doesn't
seem common to have generic bindings that cover components from multiple
vendors. In that sense I'm leaning towards separate bindings.

Rob, do you have any particular preference or suggestion?

m.

>  .../devicetree/bindings/usb/ti,usb8041.yaml   | 69 +++++++++++++++++++
>  1 file changed, 69 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/usb/ti,usb8041.yaml
> 
> diff --git a/Documentation/devicetree/bindings/usb/ti,usb8041.yaml b/Documentation/devicetree/bindings/usb/ti,usb8041.yaml
> new file mode 100644
> index 000000000000..9a49d60527b1
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/usb/ti,usb8041.yaml
> @@ -0,0 +1,69 @@
> +# SPDX-License-Identifier: GPL-2.0-only or BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/usb/ti,usb8041.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Binding for the TI USB8041 USB 3.0 hub controller
> +
> +maintainers:
> +  - Matthias Kaehlcke <mka@chromium.org>
> +
> +allOf:
> +  - $ref: usb-device.yaml#
> +
> +properties:
> +  compatible:
> +    items:
> +      - enum:
> +          - usb451,8140
> +          - usb451,8142
> +
> +  reg: true
> +
> +  reset-gpio:
> +    maxItems: 1
> +    description:
> +      GPIO specifier for GSRT# pin.
> +
> +  vdd-supply:
> +    description:
> +      phandle to the regulator that provides power to the hub.
> +
> +  peer-hub:
> +    $ref: '/schemas/types.yaml#/definitions/phandle'
> +    description:
> +      phandle to the peer hub on the controller.
> +
> +required:
> +  - peer-hub
> +  - compatible
> +  - reg
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/gpio/gpio.h>
> +
> +    usb {
> +        dr_mode = "host";
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        /* 2.0 hub on port 1 */
> +        hub_2_0: hub@1 {
> +          compatible = "usb451,8142";
> +          reg = <1>;
> +          peer-hub = <&hub_3_0>;
> +          reset-gpio = <&gpio1 11 GPIO_ACTIVE_LOW>;
> +        };
> +
> +        /* 3.0 hub on port 2 */
> +        hub_3_0: hub@2 {
> +          compatible = "usb451,8140";
> +          reg = <2>;
> +          peer-hub = <&hub_2_0>;
> +          reset-gpio = <&gpio1 11 GPIO_ACTIVE_LOW>;
> +        };
> +    };
> -- 
> 2.25.1
>