linux-kernel - Re: [PATCH v3 1/3] dt-bindings: usb: usb251xb: support usage case without I2C control

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Message-ID: <20250822-quantum-hungry-orca-e6c6cb@kuoka>
Date: Fri, 22 Aug 2025 10:17:04 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Jisheng Zhang <jszhang@...nel.org>
Cc: Richard Leitner <richard.leitner@...ux.dev>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, linux-usb@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/3] dt-bindings: usb: usb251xb: support usage case
 without I2C control

On Thu, Aug 21, 2025 at 12:17:41AM +0800, Jisheng Zhang wrote:
> Currently, the usb251xb assumes i2c control, and the corresponding
> dt node looks like the following:
> 
> i2c {
> 	usb-hub@2c {
> 		compatible = "microchip,usb2512b";
> 		reg = <0x2c>;
> 		reset-gpios = <&porta 8 GPIO_ACTIVE_LOW>;
> 	};
> };

Above is redundant, obvious from stagtement that USB can be a device on
I2C bus. Just keep it simple.

> 
> But from HW point of view, the hub supports usage case without any i2c
> control, I.E we only want the gpio controls, for example the following
> dt node:
> 
> usb-hub {
> 	compatible = "microchip,usb2512b";
> 	reset-gpios = <&porta 8 GPIO_ACTIVE_LOW>;
> };
> 
> Modify the dt-binding of usb2512b to support this usage case, and add
> usage example to the examples section.
> 
> Signed-off-by: Jisheng Zhang <jszhang@...nel.org>
> ---
>  Documentation/devicetree/bindings/usb/usb251xb.yaml | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>

Best regards,
Krzysztof