linux-kernel - Re: [PATCH v2 1/3] dt-bindings: usb: ci-hdrc-usb2: add property disable-runtime-pm

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Date:   Fri, 17 Jul 2020 02:31:09 +0000
From:   Peter Chen <peter.chen@....com>
To:     Rob Herring <robh@...nel.org>
CC:     Philippe Schenker <philippe.schenker@...adex.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] dt-bindings: usb: ci-hdrc-usb2: add property
 disable-runtime-pm

On 20-07-16 13:24:52, Rob Herring wrote:
> On Tue, Jul 14, 2020 at 05:18:20PM +0200, Philippe Schenker wrote:
> > Chipidea depends on some hardware signals to be there in order
> > for runtime-pm to work well. Add the possibility to disable runtime
> > power management that is necessary for certain boards.
> 
> This is why we have SoC specific compatible strings. Use that.

It is a board design limitation, not SoC's. To support USB low power
mode for device mode, either VBUS connects to SoC, or VBUS connect to
GPIO, or VBUS connect to Type-C IC, but none of the design is used
at that board. So the USB can't enter low power mode for that board,
otherwise, the USB controller can't be woken up since no any interrupts
will occur if USB cable (host at other side) connects to the connector.

Peter
> 
> > 
> > Signed-off-by: Philippe Schenker <philippe.schenker@...adex.com>
> > ---
> > 
> > Changes in v2: None
> > 
> >  Documentation/devicetree/bindings/usb/ci-hdrc-usb2.txt | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/usb/ci-hdrc-usb2.txt b/Documentation/devicetree/bindings/usb/ci-hdrc-usb2.txt
> > index 51376cbe5f3d..67a31df13e69 100644
> > --- a/Documentation/devicetree/bindings/usb/ci-hdrc-usb2.txt
> > +++ b/Documentation/devicetree/bindings/usb/ci-hdrc-usb2.txt
> > @@ -90,6 +90,7 @@ Optional properties:
> >    case, the "idle" state needs to pull down the data and strobe pin
> >    and the "active" state needs to pull up the strobe pin.
> >  - pinctrl-n: alternate pin modes
> > +- disable-runtime-pm: This disables the runtime power management.
> 
> This is a Linux feature, not h/w description or config.
> 
> >  
> >  i.mx specific properties
> >  - fsl,usbmisc: phandler of non-core register device, with one
> > -- 
> > 2.27.0
> > 

-- 

Thanks,
Peter Chen