linux-kernel - Re: [PATCH v4 2/3] dt-bindings: usb: snps,dwc3: Add runtime-suspend-on-usb-suspend property

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Message-ID: <20230819004250.uae3z24m45ggk67l@synopsys.com>
Date:   Sat, 19 Aug 2023 00:42:56 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Elson Serrao <quic_eserrao@...cinc.com>
CC:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        "rogerq@...nel.org" <rogerq@...nel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "conor+dt@...nel.org" <conor+dt@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: Re: [PATCH v4 2/3] dt-bindings: usb: snps,dwc3: Add
 runtime-suspend-on-usb-suspend property

On Fri, Aug 18, 2023, Elson Serrao wrote:
> 
> 
> On 8/15/2023 10:44 PM, Krzysztof Kozlowski wrote:
> > On 14/08/2023 20:50, Elson Roy Serrao wrote:
> > > This property allows dwc3 runtime suspend when bus suspend interrupt
> > > is received even with cable connected. This would allow the dwc3
> > > controller to enter low power mode during bus suspend scenario.
> > > 
> > > This property would particularly benefit dwc3 IPs where hibernation is
> > > not enabled and the dwc3 low power mode entry/exit is handled by the
> > > glue driver. The assumption here is that the platform using this dt
> > > property is capable of detecting resume events to bring the controller
> > > out of suspend.
> > > 
> > > Signed-off-by: Elson Roy Serrao <quic_eserrao@...cinc.com>
> > > ---
> > >   Documentation/devicetree/bindings/usb/snps,dwc3.yaml | 5 +++++
> > >   1 file changed, 5 insertions(+)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/usb/snps,dwc3.yaml b/Documentation/devicetree/bindings/usb/snps,dwc3.yaml
> > > index a696f23730d3..e19a60d06d2b 100644
> > > --- a/Documentation/devicetree/bindings/usb/snps,dwc3.yaml
> > > +++ b/Documentation/devicetree/bindings/usb/snps,dwc3.yaml
> > > @@ -403,6 +403,11 @@ properties:
> > >       description:
> > >         Enable USB remote wakeup.
> > > +  snps,runtime-suspend-on-usb-suspend:
> > > +    description:
> > > +      If True then dwc3 runtime suspend is allowed during bus suspend
> > > +      case even with the USB cable connected.
> > 
> > This was no tested... but anyway, this is no a DT property but OS
> > policy. There is no such thing as "runtime suspend" in the hardware,
> > because you describe one particular OS.
> > 
> > Sorry, no a DT property, drop the change entirely.
> > 
> > 
> Hi Krzysztof
> 
> Sorry my local dt checker had some issue and it did not catch these errors.
> I have rectified it now.
> 
> This dt property is mainly for skipping dwc3 controller halt when a USB
> suspend interrupt is received with usb cable connected, so that we dont
> trigger a DISCONNECT event. Perhaps a better name would reflect the true
> usage of this?
> 
> Something like snps,skip-dwc3-halt-on-usb-suspend. dwc3 cores where
> hibernation feature is not enabled/supported can use this property
> 
> Hi Thinh,Roger
> Please let me know your opinion on 'snps,skip-dwc3-halt-on-usb-suspend' as
> the quirk name.
> 

I don't consider this a quirk. If there's a quirk, something's broken.
It's a behavior of the driver depending on the hardware capability.

So, this name should reflect the capability property of the phy(s).

I'm not great with naming either. Perhaps this?
snps,delegate-wakeup-interrupt

Thanks,
Thinh