linux-kernel - Re: [PATCH 1/2] dt-bindings: usb: snps,dwc3: Allow power-domains property

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Date:   Fri, 30 Dec 2022 10:43:44 +0200
From:   Felipe Balbi <balbi@...nel.org>
To:     Rob Herring <robh@...nel.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Cc:     Heiko Stuebner <heiko@...ech.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        "linux-rockchip@...ts.infradead.org" 
        <linux-rockchip@...ts.infradead.org>,
        Johan Jonker <jbx6244@...il.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] dt-bindings: usb: snps,dwc3: Allow power-domains
 property


Hi,

Rob Herring <robh@...nel.org> writes:
> On Fri, Dec 23, 2022 at 5:57 PM Thinh Nguyen <Thinh.Nguyen@...opsys.com> wrote:
>> > Rob Herring <robh@...nel.org> writes:
>> > >> > The Rockchip RK3399 DWC3 node has 'power-domain' property which isn't
>> > >> > allowed by the schema:
>> > >> >
>> > >> > usb@...00000: Unevaluated properties are not allowed ('power-domains' was unexpected)
>> > >> >
>> > >> > Allow DWC3 nodes to have a single power-domains entry. We could instead
>> > >> > move the power-domains property to the parent wrapper node, but the
>> > >> > could be an ABI break (Linux shouldn't care). Also, we don't want to
>> > >> > encourage the pattern of wrapper nodes just to define resources such as
>> > >> > clocks, resets, power-domains, etc. when not necessary.
>> > >> >
>> > >> > Signed-off-by: Rob Herring <robh@...nel.org>
>> > >> > ---
>> > >> >  Documentation/devicetree/bindings/usb/snps,dwc3.yaml | 3 +++
>> > >> >  1 file changed, 3 insertions(+)
>> > >> >
>> > >> > diff --git a/Documentation/devicetree/bindings/usb/snps,dwc3.yaml b/Documentation/devicetree/bindings/usb/snps,dwc3.yaml
>> > >> > index 6d78048c4613..bcefd1c2410a 100644
>> > >> > --- a/Documentation/devicetree/bindings/usb/snps,dwc3.yaml
>> > >> > +++ b/Documentation/devicetree/bindings/usb/snps,dwc3.yaml
>> > >> > @@ -91,6 +91,9 @@ properties:
>> > >> >          - usb2-phy
>> > >> >          - usb3-phy
>> > >> >
>> > >> > +  power-domains:
>> > >> > +    maxItems: 1
>> > >>
>> > >> AFAICT this can be incorrect. Also, you could have Cc the dwc3
>> > >> maintainer to get comments.
>>
>> Felipe is correct. We have 2 power-domains: Core domain and PMU.
>
> Power management unit? Performance management unit?
>
> That doesn't change that the rk3399 is 1 and we're stuck with it. So I
> can say 1 or 2 domains, or we add the 2nd domain when someone needs
> it.

Isn't the snps,dwc3.yaml document supposed to document dwc3's view of
the world? In that case, dwc3 expects 2 power domains. It just so
happens that in rk3399 they are fed from the same power supply, but
dwc3' still thinks there are two of them. No?

It's a similar situation when you have multiple clock domains with the
same parent clock.

-- 
balbi