linux-kernel - Re: [PATCH 1/2] dt-bindings: usb: Add documentation for AM62 USB Wrapper module

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Date:   Wed, 23 Mar 2022 10:21:40 +0100
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Aswath Govindraju <a-govindraju@...com>
Cc:     linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-usb@...r.kernel.org, Felipe Balbi <balbi@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Roger Quadros <rogerq@...nel.org>,
        Vignesh Raghavendra <vigneshr@...com>,
        Kishon Vijay Abraham I <kishon@...com>
Subject: Re: [PATCH 1/2] dt-bindings: usb: Add documentation for AM62 USB
 Wrapper module

On 23/03/2022 10:17, Aswath Govindraju wrote:
> Hi Krzysztof,

(...)

>>> +
>>> +  ti,syscon-phy-pll-refclk:
>>> +    $ref: /schemas/types.yaml#/definitions/phandle-array
>>> +    items:
>>> +      - items:
>>> +          - description: Phandle to the SYSCON entry
>>> +          - description: USB phy control register offset within SYSCON
>>> +    description: Specifier for configuring frequency of ref clock input.
>>
>> This is a bit strange. The ref clock is the "ref" input clock, right? In
>> such case use clk_set_rate()... Using syscon for managing clocks is not
>> the proper way.
>>
> 
> The syscon property is not being used to set the ref clock frequency but
> is rather being used to indicate the input clock frequency for USB PHY
> operation. I think the description seems be misleading. I will update it
> in the respin, to reflect the above description.

Yes, please, it will help.

> 
>> Plus all the issues pointed out by Roger.
>>
>>> +
>>> +  '#address-cells':
>>> +    const: 2
>>> +
>>> +  '#size-cells':
>>> +    const: 2
>>
>> No children allowed?
>>
>> I understand this is a wrapper, which explains why you do not include
>> usb-hcd.yaml schema. But since it is a wrapper, what is it wrapping?
>>
> 
> Yes, there is a child node, which would be the dwc3-contoller node.
> Would adding the child node too in the example help capture this better?

Yes, please, because then you will also spot errors when running
dt_binding_check.

You need patternProperties for "^usb@[0-9a-f]+$" referencing Synopsys
schema. Something like:
Documentation/devicetree/bindings/usb/samsung,exynos-dwc3.yaml



Best regards,
Krzysztof