From mboxrd@z Thu Jan  1 00:00:00 1970
From: Chunfeng Yun <chunfeng.yun@mediatek.com>
Subject: Re: [PATCH v2 2/6] dt-bindings: usb: add binding for Type-B dual
 role switch by GPIO
Date: Fri, 15 Mar 2019 15:52:54 +0800
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To: Rob Herring <robh+dt@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Heikki Krogerus <heikki.krogerus@linux.intel.com>, Mark Rutland <mark.rutland@arm.com>, Matthias Brugger <matthias.bgg@gmail.com>, Adam Thomson <Adam.Thomson.Opensource@diasemi.com>, Li Jun <jun.li@nxp.com>, Badhri Jagan Sridharan <badhri@google.com>, Hans de Goede <hdegoede@redhat.com>, Andy Shevchenko <andy.shevchenko@gmail.com>, Min Guo <min.guo@mediatek.com>, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org
List-Id: devicetree@vger.kernel.org

Hi Rob,

There are two ways that I think out to support type-B GPIO based dual
role switch.

The first one, as the series used:

&mtu3 {
    status = "okay";

    connector@0 {
        compatible = "usb-b-connector", "linux,typeb-switch-gpio";
        label = "micro-USB";
        type = "micro";
        id-gpio = <&pio 12 GPIO_ACTIVE_HIGH>;
        vbus-supply = <&usb_p0_vbus>;
    };
};

but there are some shortcomings:
1. It's not transparent, USB controller driver should be modified, and
call of_platform_populate() to create platform device for connector,
this is not friendly when the controller driver hasn't child node
before, and also not compatible with other cases, such as Type-C

2. It doesn't keep format consistent with the case using Type-C, or
using PMIC to detect ID pin.

3. vbus-supply will be got by USB controller driver if it aready
supports it


another way as following:

role_sw_iddig {
    compatible = "linux,typeb-switch-gpio";
    status = "okay";

    connector {
        compatible = "usb-b-connector";
        label = "micro-USB";
        type = "micro";
        id-gpios = <&pio 12 GPIO_ACTIVE_HIGH>;
        vbus-supply = <&usb_p0_vbus>;
    };

    port {
        bsw_ep: endpoint@0 {
            remote-endpoint = <&usb_role_sw>;
        };
    };
};

&mtu3 {
    status = "okay";

    port {
        usb_role_sw: endpoint@0 {
            remote-endpoint = <&bsw_ep>;
        };
    };
};

strength:
avoid the shortcomings of the first way
shortcoming:
it's a virtual device and seems not following graph.txt binding,

Do you have any suggestion?

Thanks


On Fri, 2019-03-15 at 15:38 +0800, Chunfeng Yun wrote:
> It's used to support dual role switch via GPIO when use Type-B
> receptacle
> 
> Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
> ---
> v2 changes:
>   1. new patch to make binding clear suggested by Hans
> ---
>  .../bindings/usb/typeb-switch-gpio.txt        | 26 +++++++++++++++++++
>  1 file changed, 26 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/usb/typeb-switch-gpio.txt
> 
> diff --git a/Documentation/devicetree/bindings/usb/typeb-switch-gpio.txt b/Documentation/devicetree/bindings/usb/typeb-switch-gpio.txt
> new file mode 100644
> index 000000000000..d46d83bc6500
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/usb/typeb-switch-gpio.txt
> @@ -0,0 +1,26 @@
> +USB Type-B dual role switch via a GPIO
> +
> +This is a virtual device used to switch dual role mode from the USB ID pin
> +connected to a GPIO pin.
> +
> +Required properties:
> +- compatible: Should be "linux,typeb-switch-gpio"
> +
> +Either one of id-gpios or vbus-gpios must be present, and both can be present
> +as well.
> +vbus-supply could be present if needed when support dual role mode.
> +	see connector/usb-connector.txt
> +
> +Example:
> +
> +&mtu3 {
> +	status = "okay";
> +
> +	connector@0 {
> +		compatible = "usb-b-connector", "linux,typeb-switch-gpio";
> +		label = "micro-USB";
> +		type = "micro";
> +		id-gpio = <&pio 12 GPIO_ACTIVE_HIGH>;
> +		vbus-supply = <&usb_p0_vbus>;
> +	};
> +};