linux-kernel - Re: [PATCH 1/2] dt-bindings: usb: qcom,pmic-typec: drop port description

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Date: Fri, 22 Mar 2024 21:08:18 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Rob Herring <robh@...nel.org>
Cc: "Bryan O'Donoghue" <bryan.odonoghue@...aro.org>, neil.armstrong@...aro.org, 
	Bjorn Andersson <andersson@...nel.org>, Konrad Dybcio <konrad.dybcio@...aro.org>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: usb: qcom,pmic-typec: drop port description

On Fri, 22 Mar 2024 at 20:36, Rob Herring <robh@...nel.org> wrote:
>
> On Fri, Mar 22, 2024 at 05:49:00PM +0200, Dmitry Baryshkov wrote:
> > On Fri, 22 Mar 2024 at 17:23, Bryan O'Donoghue
> > <bryan.odonoghue@...aro.org> wrote:
> > >
> > > On 22/03/2024 15:09, neil.armstrong@...aro.org wrote:
> > > >> TBH I think we should drop this HS, SS stuff from the connector
> > > >> definition - there's nothing to say in a h/w definition anywhere HS
> > > >> must be a port or indeed SS - not all hardware knows or cares about
> > > >> different HS/SS signalling.
> > > >
> > > > It matches the USB-C connector electrical characteristics, which by spec
> > > > has, at least:
> > > > - High-Speed USB Line
> > > > - up to 4 differential high-speed lanes that can be switched to DP, USB2
> > > > or PCIe
> > > > - SideBand line (SBU)
> > > >
> > > > And those 3 components can be handled by 3 different HW in the SoC, so
> > > > each one has a dedicated port.
> > > >
> > > > Remember DT describes the HW, not the SW implementation.
> > > >
> > > > Neil
> > >
> > > Yes, you're right about that.
> > >
> > > I suppose
> > >
> > > 1. Orientation switches should be defined as coming from a port on the
> > >     connector associated with the CC pins.
> > >     port@3:
> > >     orientation-switch port name goes here
> > >
> > > 2. Data-role switches...
> > >     Again the CC pins
> > >
> > > https://community.silabs.com/s/article/what-s-the-role-of-cc-pin-in-type-c-solution?language=en_US
> > >
> > > Maybe the right-thing-to-do is to add another port for the CC pins -
> > > which would still describe the hardware characteristics but would
> > > _accurately_ name the thing which does the data-role/orientation switching
> >
> > It's true that we don't describe CC lines. However In most of the
> > cases CC lines are handled by the Type-C port manager directly. So
> > there will be a connection from usb-c-connector to the pmic-typec
> > itself (which looks pretty redundant).
>
> The thought at the time this was designed was that would be the parent
> node of the connector. That's perhaps too simple.

Yep. In both our cases the TCPM is a parent of the usb-c-connector.


-- 
With best wishes
Dmitry