linux-kernel - Re: [PATCH 1/7] dt-bindings: phy: qcom,sc8280xp-qmp-usb43dp: Add ports and orientation-switch

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Date:   Thu, 4 May 2023 07:51:37 -0700
From:   Bjorn Andersson <quic_bjorande@...cinc.com>
To:     Neil Armstrong <neil.armstrong@...aro.org>
CC:     Bryan O'Donoghue <pure.logic@...us-software.ie>,
        Vinod Koul <vkoul@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Johan Hovold <johan@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-phy@...ts.infradead.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/7] dt-bindings: phy: qcom,sc8280xp-qmp-usb43dp: Add
 ports and orientation-switch

On Thu, May 04, 2023 at 03:50:53PM +0200, Neil Armstrong wrote:
> On 27/04/2023 21:52, Bjorn Andersson wrote:
> > On Wed, Apr 26, 2023 at 11:21:29AM +0100, Bryan O'Donoghue wrote:
> > > On Tue, Apr 25, 2023 at 4:40 AM Bjorn Andersson
> > > <quic_bjorande@...cinc.com> wrote:
> > > > 
> > > > The QMP combo phy can be connected to a TCPM, a USB controller and a
> > > > DisplayPort controller for handling USB Type-C orientation switching
> > > > and propagating HPD signals.
> > > > 
> > > > Extend the binding to allow these connections to be described.
> > > > 
> > > > Signed-off-by: Bjorn Andersson <quic_bjorande@...cinc.com>
> > > > ---
> > > >   .../phy/qcom,sc8280xp-qmp-usb43dp-phy.yaml    | 51 +++++++++++++++++++
> > > >   1 file changed, 51 insertions(+)
> > > > 
> > > > diff --git a/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-usb43dp-phy.yaml b/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-usb43dp-phy.yaml
> > > > index 3cd5fc3e8fab..c037ac90ce7f 100644
> > > > --- a/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-usb43dp-phy.yaml
> > > > +++ b/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-usb43dp-phy.yaml
> > > > @@ -60,6 +60,26 @@ properties:
> > > >       description:
> > > >         See include/dt-bindings/dt-bindings/phy/phy-qcom-qmp.h
> > > > 
> > > > +  orientation-switch:
> > > > +    description:
> > > > +      Flag the PHY as possible handler of USB Type-C orientation switching
> > > > +    type: boolean
> > > > +
> > > > +  ports:
> > > > +    $ref: /schemas/graph.yaml#/properties/ports
> > > > +    properties:
> > > > +      port@0:
> > > > +        $ref: /schemas/graph.yaml#/properties/port
> > > > +        description: Output endpoint of the PHY
> > > > +
> > > > +      port@1:
> > > > +        $ref: /schemas/graph.yaml#/$defs/port-base
> > > > +        description: Incoming endpoint from the USB controller
> > > 
> > > Do you really need this one ?
> > > 
> > > The controller doesn't process orientation switching.
> > > 
> > 
> > I don't have a need for it, as we can deal with role switching by
> > connecting connector/port@0 to the dwc3.
> > 
> > But if we ever have a need to describe the dwc3 -> QMP -> connector path
> > in the of_graph I think it would look prettier to have USB input as
> > port@1 and DP input as port@....
> 
> I think it would be great to have port@1 for USB SS and port@2 for DP,
> otherwise we need to add 2 endpoints as I sent in
> https://lore.kernel.org/all/20230503-topic-sm8450-graphics-dp-next-v1-1-d1ee9397f2a6@linaro.org/
> since we split USB HS and SS streams on SM8[345]50 platforms.
> 

Right, so let's keep port@1 and port@2 in the binding, and then we can
choose to connect port@1 to DWC3 or not...

Regards,
Bjorn

> > 
> > Do you have a concern with keeping it around in the DT (the
> > implementation doesn't need to care)?
> > 
> > Regards,
> > Bjorn
>