linux-kernel - Re: [PATCH v5 1/4] dt-bindings: usb: Add binding for discrete onboard USB hubs

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Date:   Wed, 17 Feb 2021 15:04:41 -0600
From:   Rob Herring <robh@...nel.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Frank Rowand <frowand.list@...il.com>,
        devicetree@...r.kernel.org, Peter Chen <peter.chen@....com>,
        Stephen Boyd <swboyd@...omium.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Ravi Chandra Sadineni <ravisadineni@...omium.org>,
        Bastien Nocera <hadess@...ess.net>,
        linux-kernel@...r.kernel.org,
        Douglas Anderson <dianders@...omium.org>,
        linux-usb@...r.kernel.org, Krzysztof Kozlowski <krzk@...nel.org>
Subject: Re: [PATCH v5 1/4] dt-bindings: usb: Add binding for discrete
 onboard USB hubs

On Wed, Feb 10, 2021 at 09:10:36AM -0800, Matthias Kaehlcke wrote:
> Discrete onboard USB hubs (an example for such a hub is the Realtek
> RTS5411) need to be powered and may require initialization of other
> resources (like GPIOs or clocks) to work properly. This adds a device
> tree binding for these hubs.
> 
> Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
> ---
> 
> Changes in v5:
> - updated 'title'
> - only use standard USB compatible strings
> - deleted 'usb_hub' node
> - renamed 'usb_controller' node to 'usb-controller'
> - removed labels from USB nodes
> - added 'vdd-supply' to USB nodes
> 
> Changes in v4:
> - none
> 
> Changes in v3:
> - updated commit message
> - removed recursive reference to $self
> - adjusted 'compatible' definition to support multiple entries
> - changed USB controller phandle to be a node
> 
> Changes in v2:
> - removed 'wakeup-source' and 'power-off-in-suspend' properties
> - consistently use spaces for indentation in example
> 
>  .../bindings/usb/onboard_usb_hub.yaml         | 49 +++++++++++++++++++
>  1 file changed, 49 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/usb/onboard_usb_hub.yaml
> 
> diff --git a/Documentation/devicetree/bindings/usb/onboard_usb_hub.yaml b/Documentation/devicetree/bindings/usb/onboard_usb_hub.yaml
> new file mode 100644
> index 000000000000..bf4ec52e6c7b
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/usb/onboard_usb_hub.yaml
> @@ -0,0 +1,49 @@
> +# SPDX-License-Identifier: GPL-2.0-only or BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/usb/onboard_usb_hub.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Binding for discrete onboard USB hubs

This isn't really generic. Maybe there's a set of hubs with only a 
single supply much like 'simple-panel', but I kind of doubt that here. 
There aren't hundreds of hub chips like panels. Though, we should put 
this into bindings/usb/hub/ so we start collecting hub bindings in one 
place.

A generic driver doesn't have to have a generic binding. You can have a 
specific device binding which is handled by a generic driver. Or not. 
Who knows. Maybe a simple user like u-boot has a generic driver while 
something more feature rich has a device specific binding.

> +
> +maintainers:
> +  - Matthias Kaehlcke <mka@...omium.org>

Now we have usb-device.yaml, you need:

allOf:
  - $ref: usb-device.yaml#

> +
> +properties:
> +  compatible:
> +    items:
> +      - enum:
> +        - usbbda,5411
> +        - usbbda,411
> +
> +  vdd-supply:
> +    description:
> +      phandle to the regulator that provides power to the hub.
> +
> +required:
> +  - compatible
> +  - vdd-supply
> +
> +examples:
> +  - |
> +    usb-controller {
> +        dr_mode = "host";
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        /* 2.0 hub on port 1 */
> +        hub_2_0: hub@1 {
> +            compatible = "usbbda,5411";
> +            reg = <1>;
> +            vdd-supply = <&pp3300_hub>;
> +        };
> +
> +        /* 3.0 hub on port 2 */
> +        hub_3_0: hub@2 {
> +            compatible = "usbbda,411";
> +            reg = <2>;
> +            vdd-supply = <&pp3300_hub>;
> +        };
> +    };
> +
> +...
> -- 
> 2.30.0.478.g8a0d178c01-goog
>