Re: [PATCH 1/3] dt-bindings: usb: fsa4480: Add data-lanes property to endpoint

Rob Herring
2023-10-17T19:12:41Z

On Mon, Oct 16, 2023 at 04:32:55PM +0200, Neil Armstrong wrote:
> On 16/10/2023 16:22, Rob Herring wrote:
> > On Fri, Oct 13, 2023 at 01:38:05PM +0200, Luca Weiss wrote:
> > > Allow specifying data-lanes to reverse the SBU muxing orientation where
> > > necessary by the hardware design.
> >
> > What situation in the hardware design makes this necessary. Please
> > describe the problem.
> >
> > >
> > > Signed-off-by: Luca Weiss <luca.weiss@fairphone.com>
> > > ---
> > > .../devicetree/bindings/usb/fcs,fsa4480.yaml | 29 +++++++++++++++++++++-
> > > 1 file changed, 28 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/Documentation/devicetree/bindings/usb/fcs,fsa4480.yaml b/Documentation/devicetree/bindings/usb/fcs,fsa4480.yaml
> > > index f6e7a5c1ff0b..86f6d633c2fb 100644
> > > --- a/Documentation/devicetree/bindings/usb/fcs,fsa4480.yaml
> > > +++ b/Documentation/devicetree/bindings/usb/fcs,fsa4480.yaml
> > > @@ -32,10 +32,37 @@ properties:
> > > type: boolean
> > > port:
> > > - $ref: /schemas/graph.yaml#/properties/port
> > > + $ref: /schemas/graph.yaml#/$defs/port-base
> > > description:
> > > A port node to link the FSA4480 to a TypeC controller for the purpose of
> > > handling altmode muxing and orientation switching.
> > > + unevaluatedProperties: false
> > > +
> > > + properties:
> > > + endpoint:
> > > + $ref: /schemas/graph.yaml#/$defs/endpoint-base
> > > + unevaluatedProperties: false
> > > +
> > > + properties:
> > > + data-lanes:
> > > + $ref: /schemas/types.yaml#/definitions/uint32-array
> > > + description:
> > > + Specifies how the AUX+/- lines are connected to SBU1/2.
> >
> > Doesn't this depend on the connector orientation? Or it is both that and
> > the lines can be swapped on the PCB?
> >
> > Seems like an abuse of data-lanes which already has a definition which
> > is not about swapping + and - differential lanes.
>
> The FSA acts as a mux between DP AUX, Audio lanes on one side and
> the USB-C SBU lanes on the other side.
> _______ ______
> | | |
> |-- HP --| |
> |-- MIC --| |or
> SoC | | MUX |-- SBU1 ---> To the USB-C
> Codec |-- AUX+ --| |-- SBU2 ---> connected
> |-- AUX- --| |
> ______| |____ |
>
> The SBU1 & SBU2 are connected to the USB-C connector, and the actual orientation
> to the connected devices/cable/whatever is determined by the TPCM and the MUX in
> the FSA4480 with be dynamically changed according to the CC1/CC2 detection and PD alt mode.
>
> But on the other side the orientation of the AUX+/AUX- connected to the SoC
> is not tied to the USB-C orientation but how it's routed on the PCB.
>
> This describes how the AUX+/AUX- are physically routed to the FSA4480 chip.

I'd hate for this ASCII art to go to waste. Please add this detail to
the commit message.

Rob