linux-kernel - Re: [PATCH v3 1/2] dt-bindings: phy: Add Sophgo CV1800 USB phy

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Date: Mon, 6 May 2024 20:17:30 +0800
From: Inochi Amaoto <inochiama@...look.com>
To: Krzysztof Kozlowski <krzk@...nel.org>, 
	Inochi Amaoto <inochiama@...look.com>, Vinod Koul <vkoul@...nel.org>, 
	Kishon Vijay Abraham I <kishon@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Chen Wang <unicorn_wang@...look.com>, Paul Walmsley <paul.walmsley@...ive.com>, 
	Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>
Cc: Jisheng Zhang <jszhang@...nel.org>, Liu Gui <kenneth.liu@...hgo.com>, 
	Jingbao Qiu <qiujingbao.dlmu@...il.com>, dlan@...too.org, linux-phy@...ts.infradead.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v3 1/2] dt-bindings: phy: Add Sophgo CV1800 USB phy

On Mon, May 06, 2024 at 08:51:59AM GMT, Krzysztof Kozlowski wrote:
> On 05/05/2024 03:52, Inochi Amaoto wrote:
> > The USB phy of Sophgo CV18XX series SoC needs to sense a pin called
> > "VBUS_DET" to get the right operation mode. If this pin is not
> > connected, it only supports setting the mode manually.
> > 
> > Add USB phy bindings for Sophgo CV18XX/SG200X series SoC.
> 
> ...
> 
> > +
> > +  clock-names:
> > +    items:
> > +      - const: phy
> > +      - const: app
> > +      - const: stb
> > +      - const: lpm
> > +
> > +  vbus_det-gpios:
> 
> No underscores.
> 

Thanks.

> > +    description: GPIO to the USB OTG VBUS detect pin. This should not be
> > +      defined if vbus_det pin and switch pin are connected, which may
> > +      break the VBUS detection.
> 
> Why is this property of the PHY? VBUS pin goes to the connector, doesn't
> it? It looks like you combined two or three (!!!) bindings into one.
> 

Yes, but I am not sure which is the best to write this bindings.
The topology of USB likes this:

controller -- phy -- switch --> (host) port/hub
                            --> (device) port

The vbus-detect connect to the device port, but it will change the mode for
both phy and switch. And the switch is just a switching circuit.
I am pretty confused on how to split this binding. I think it may like the 
following:

phy {
	switch {
		/* This is the switch in the follows */
		connector1 {
			/* host port */
		};
		connector2 {
			/* device port*/
			/* the vbus pin is here */
		};
	};
};

Could you share some suggestion on this?

> > +    maxItems: 1
> > +
> > +  sophgo,switch-gpios:
> > +    description: GPIO array for the phy to control connected switch. For
> 
> Switch? This is a binding of the phy, not switch...
> 

You are right, I think this switch may be more like a pattern device.

> > +      host mode, the driver will set these GPIOs to low one by one. For
> 
> Yeah, you mention driver which further confirms this is a property for
> driver, not hardware.
> 
> Describe your hardware, not driver behavior.

OK, I will remove this.

> 
> 
> > +      device mode, the driver will set these GPIOs to high in reverse
> > +      order. For a reference design, see item description.
> > +    minItems: 1
> > +    items:
> > +      - description: USB switch operation mode
> > +      - description: USB switch host power control
> > +
> > +required:
> > +  - compatible
> > +  - "#phy-cells"
> > +  - clocks
> > +  - clock-names
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    phy@48 {
> > +      compatible = "sophgo,cv1800-usb-phy";
> > +      reg = <0x48 0x4>;
> > +      #phy-cells = <0>;
> > +      clocks = <&clk 92>, <&clk 93>,
> > +               <&clk 94>, <&clk 95>;
> > +      clock-names = "phy", "app", "stb", "lpm";
> 
> Make the example complete.
> 
> 
> 
> Best regards,
> Krzysztof
>