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

[Neil Armstrong]

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@xxxxxxxxxxxxx>
> > ---
> >   .../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.

Neil

> Rob