linux-kernel - Re: [RESEND PATCH v3 1/4] dt-bindings: connector: add power-opmode optional property to usb-connector

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Date:   Wed, 4 Nov 2020 15:08:03 -0600
From:   Rob Herring <robh@...nel.org>
To:     Amelie DELAUNAY <amelie.delaunay@...com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Russell King <linux@...linux.org.uk>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linux USB List <linux-usb@...r.kernel.org>,
        "moderated list:ARM/STM32 ARCHITECTURE" 
        <linux-stm32@...md-mailman.stormreply.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Fabrice Gasnier <fabrice.gasnier@...com>
Subject: Re: [RESEND PATCH v3 1/4] dt-bindings: connector: add power-opmode
 optional property to usb-connector

On Fri, Oct 30, 2020 at 04:27:14PM +0100, Amelie DELAUNAY wrote:
> 
> 
> On 10/30/20 3:29 PM, Rob Herring wrote:
> > On Thu, Oct 29, 2020 at 11:49 AM Amelie DELAUNAY <amelie.delaunay@...com> wrote:
> > > 
> > > 
> > > 
> > > On 10/29/20 4:40 PM, Rob Herring wrote:
> > > > On Thu, Oct 29, 2020 at 10:58:03AM +0100, Amelie Delaunay wrote:
> > > > > Power operation mode may depends on hardware design, so, add the optional
> > > > > property power-opmode for usb-c connector to select the power operation
> > > > > mode capability.
> > > > > 
> > > > > Signed-off-by: Amelie Delaunay <amelie.delaunay@...com>
> > > > > ---
> > > > >    .../bindings/connector/usb-connector.yaml      | 18 ++++++++++++++++++
> > > > >    1 file changed, 18 insertions(+)
> > > > > 
> > > > > diff --git a/Documentation/devicetree/bindings/connector/usb-connector.yaml b/Documentation/devicetree/bindings/connector/usb-connector.yaml
> > > > > index 728f82db073d..200d19c60fd5 100644
> > > > > --- a/Documentation/devicetree/bindings/connector/usb-connector.yaml
> > > > > +++ b/Documentation/devicetree/bindings/connector/usb-connector.yaml
> > > > > @@ -93,6 +93,24 @@ properties:
> > > > >          - device
> > > > >          - dual
> > > > > 
> > > > > +  power-opmode:
> > > > 
> > > > I've acked this version:
> > > > 
> > > > https://lore.kernel.org/r/20201020093627.256885-2-badhri@google.com
> > > > 
> > > 
> > > frs is used for Fast Role Swap defined in USB PD spec.
> > > I understand it allows to get the same information but I'm wondering why
> > > the property name is limited to -frs- in this case. What about a
> > > non-power delivery USB-C connector ?
> > 
> > I've got no idea. The folks that know USB-C and PD details need to get
> > together and work all this out. To me, it looks like the same thing...
> > 
> 
> It looks but...
> 
> The purpose of power-opmode property is to configure the USB-C controllers,
> especially the non-PD USB-C controllers to determine the power operation
> mode that the Type C connector will support and will advertise through CC
> pins when it has no power delivery support, whatever the power role: Sink,
> Source or Dual
> The management of the property is the same that data-role and power-role
> properties, and done by USB Type-C Connector Class.
> 
> new-source-frs-typec-current specifies initial current capability of the new
> source when vSafe5V is applied during PD3.0 Fast Role Swap. So here, this
> property is not applied at usb-c controller configuration level, but during
> PD Fast Role Swap, so when the Sink become the Source.
> Moreover, the related driver code says FRS can only be supported by DRP
> ports. So new-source-frs-typec-current property, in addition to being
> specific to PD, is also dedicated to DRP usb-c controller.
> The property is managed by Type-C Port Controller Manager for PD.

But it's the same set of possible values, right? So we can align the 
values at least.

Can we align the names in some way? power-opmode and frs-source-opmode 
or ??

Are these 2 properties mutually exclusive? If so, that should be 
captured.

Rob