linux-kernel - Re: [PATCH 2/2] dt-bindings: usb: rockchip,dwc3: Move RK3399 to its own schema

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Date:   Fri, 23 Dec 2022 12:34:26 +0200
From:   Felipe Balbi <balbi@...nel.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Heiko Stuebner <heiko@...ech.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        linux-rockchip@...ts.infradead.org,
        Johan Jonker <jbx6244@...il.com>,
        linux-arm-kernel@...ts.infradead.org, linux-usb@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] dt-bindings: usb: rockchip,dwc3: Move RK3399 to its
 own schema

Rob Herring <robh@...nel.org> writes:

> On Tue, Dec 20, 2022 at 1:37 AM Felipe Balbi <balbi@...nel.org> wrote:
>>
>> Rob Herring <robh@...nel.org> writes:
>>
>> > The rockchip,dwc3.yaml schema defines a single DWC3 node, but the RK3399
>> > uses the discouraged parent wrapper node and child 'generic' DWC3 node.
>>
>> Why discouraged? Splitting those two separate devices (yes, they are
>> separate physical modules) has greatly simplified e.g. power management
>> and encapsulation of the core module.
>
> Sometimes they are separate and that's fine, but often it's just
> different clocks, resets, etc. and that's no different from every
> other block.

Right, then the argument is that all other blocks are not modelling the
HW as they should :)

> If there's wrapper registers or something clearly extra, then I agree
> a wrapper parent node makes sense.

There's always wrapper-specific registers. Some wrappers even add custom
functionality. IIRC Qcom added a HW-based URB "scheduler" or some sort.

> Otherwise, for cases like RK3399, I don't think it does, but we're
> stuck with it now.
>
> Also, we have this pattern pretty much nowhere else and DWC3 is not
> special.

No, it's not. But it could just be the first example of the driver
actually modelling the underlying HW.

In any case, I was just curious with your opinion that this model is
discouraged, as it's not stated anywhere in the kernel's documentation.

Happy holidays

-- 
balbi

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