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

Neil Armstrong
2023-10-16T14:33:01Z

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.

Neil

>
> Rob