Re: [PATCH v7 7/8] dt-bindings: misc: Add bindings for HiSilicon usb hub and data role switch functionality on HiKey960

[Rob Herring <robh@kernel.org>]

On Thu, Dec 12, 2019 at 01:42:32AM +0000, John Stultz wrote:
> From: Yu Chen <chenyu56@huawei.com>
> 
> This patch adds binding documentation to support usb hub and usb
> data role switch of Hisilicon HiKey960 Board.
> 
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Rob Herring <robh+dt@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> CC: ShuFan Lee <shufan_lee@richtek.com>
> Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
> Cc: Chunfeng Yun <chunfeng.yun@mediatek.com>
> Cc: Yu Chen <chenyu56@huawei.com>
> Cc: Felipe Balbi <balbi@kernel.org>
> Cc: Hans de Goede <hdegoede@redhat.com>
> Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
> Cc: Jun Li <lijun.kernel@gmail.com>
> Cc: Valentin Schneider <valentin.schneider@arm.com>
> Cc: Guillaume Gardet <Guillaume.Gardet@arm.com>
> Cc: Jack Pham <jackp@codeaurora.org>
> Cc: linux-usb@vger.kernel.org
> Cc: devicetree@vger.kernel.org
> Signed-off-by: Yu Chen <chenyu56@huawei.com>
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> ---
> v3: Reworked as usb-role-switch intermediary
> 
> v7: Switched over to YAML dt binding description
> ---
>  .../bindings/misc/hisilicon-hikey-usb.yaml    | 85 +++++++++++++++++++
>  1 file changed, 85 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/misc/hisilicon-hikey-usb.yaml
> 
> diff --git a/Documentation/devicetree/bindings/misc/hisilicon-hikey-usb.yaml b/Documentation/devicetree/bindings/misc/hisilicon-hikey-usb.yaml
> new file mode 100644
> index 000000000000..1fc3b198ef73
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/misc/hisilicon-hikey-usb.yaml
> @@ -0,0 +1,85 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +# Copyright 2019 Linaro Ltd.
> +%YAML 1.2
> +---
> +$id: "http://devicetree.org/schemas/misc/hisilicon-hikey-usb.yaml#"
> +$schema: "http://devicetree.org/meta-schemas/core.yaml#"
> +
> +title: HiKey960 onboard USB GPIO Hub
> +
> +maintainers:
> +  - John Stultz <john.stultz@linaro.org>
> +
> +description: |
> +  Supports the onboard HiKey960 USB GPIO hub, which acts as a
> +  role-switch intermediary to detect the state of the USB-C
> +  port, to switch the hub into dual-role USB-C or host mode,
> +  which enables the onboard USB-A host ports.

Honestly I'm torn between whatever works for you because this is pretty 
"special" dev board design and it should more accurately match the 
hardware design. I think we can do the later and it doesn't really need 
anything new.

> +
> +  Schematics about the hub can be found here:
> +    https://github.com/96boards/documentation/raw/master/consumer/hikey/hikey960/hardware-docs/HiKey960_Schematics.pdf
> +
> +properties:
> +  compatible:
> +    items:
> +      - const: hisilicon,gpio_hubv1

As a whole this is HiSilicon specific, but really it is not. It's really 
just a hub, a mux, and connectors for which we have bindings for. I 
think you need to model the actual hub in DT. We have 2 ways already to 
describe hubs in DT: a I2C device or USB device. 

AIUI, the board looks something like this:

ctrl -> mux --> hub -> type-a connector
            +-> type-c connector

If the hub I2C is not used, then you could do something like this:

ctrl {
    mux-controls = <&usb_gpio_mux>;
    connector@0 {
	// type C connector binding
    };
    hub@1 {
	// USB device binding
    };
};

Or if I2C is used and the hub is under the I2C controller:

ctrl {
    port@0 {
        mux-controls = <&usb_gpio_mux>;
        endpoint@0 { // mux state 0
		remote-endpoint = <&usb_c_connector_port>;
	};
        endpoint@1 { // mux state 1
		remote-endpoint = <&usb_hub_port>;
	};
};

The only new bindings you really need are adding 'mux-controls' to the 
USB host controller and the hub binding (we already have a few).

If the USB2 and USB3 signals come from 2 different host controller 
nodes, then I think it will need to look like the 2nd case regardless 
of I2C. (It's strange that USB3 was not routed to Type-C connector. Can 
you do USB2 on Type-C and USB3 on hub simultaneously? You need USB2 to 
enumerate, right?)

> +
> +  typec-vbus-gpios:
> +    $ref: /schemas/types.yaml#/definitions/phandle
> +    description: phandle to the typec-vbus gpio

This should be modeled as a GPIO regulator, and belongs as part of a 
connector node. See bindings/connector/usb-connector.txt.

> +
> +  otg-switch-gpios:
> +    $ref: /schemas/types.yaml#/definitions/phandle
> +    description: phandle to the otg-switch gpio

This would be the gpio-mux binding instead.

> +
> +  hub-vdd33-en-gpios:
> +    $ref: /schemas/types.yaml#/definitions/phandle
> +    description: phandle to the hub 3.3v power enablement gpio

This should be modeled as a GPIO regulator. 

What about the reset line on the hub?

> +
> +  usb-role-switch:
> +    $ref: /schemas/types.yaml#/definitions/flag
> +    description: Support role switch.

This normally is a controller property. Role switch is foreign to the 
hub, so doesn't really belong there for sure.

> +
> +  port:
> +    description: |
> +      any connector to the data bus of this controller should be modelled
> +      using the OF graph bindings specified, if the "usb-role-switch"
> +      property is used. Note for this driver, two ports are supported,
> +      the first being the endpoint that will be notified by this driver,
> +      and the second being the endpoint that notifies this driver of a
> +      role switch.
> +
> +
> +required:
> +  - compatible
> +  - typec-vbus-gpios
> +  - otg-switch-gpios
> +  - hub-vdd33-en-gpios
> +  - usb-role-switch
> +  - port
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    hisi_hikey_usb: hisi_hikey_usb {
> +        compatible = "hisilicon,gpio_hubv1";
> +        typec-vbus-gpios = <&gpio25 2 GPIO_ACTIVE_HIGH>;
> +        otg-switch-gpios = <&gpio25 6 GPIO_ACTIVE_HIGH>;
> +        hub-vdd33-en-gpios = <&gpio5 6 GPIO_ACTIVE_HIGH>;
> +        usb-role-switch;
> +
> +        port {
> +            #address-cells = <1>;
> +            #size-cells = <0>;
> +
> +            hikey_usb_ep0: endpoint@0 {
> +                reg = <0>;
> +                remote-endpoint = <&dwc3_role_switch>;
> +            };
> +            hikey_usb_ep1: endpoint@1 {
> +                reg = <1>;
> +                remote-endpoint = <&rt1711h_ep>;
> +            };
> +        };
> +    };
> -- 
> 2.17.1
>