Re: [RFC PATCH v2 1/6] dt-bindings: add bindings for USB physical connector

[Rob Herring]

On Tue, Feb 20, 2018 at 2:10 AM, Andrzej Hajda <a.hajda@xxxxxxxxxxx> wrote:
> On 19.02.2018 15:28, Rob Herring wrote:
>> On Thu, Feb 15, 2018 at 11:39:15AM +0100, Andrzej Hajda wrote:
>>> These bindings allow to describe most known standard USB connectors
>>> and it should be possible to extend it if necessary.
>>> USB connectors, beside USB can be used to route other protocols,
>>> for example UART, Audio, MHL. In such case every device passing data
>>> through the connector should have appropriate graph bindings.
>>>
>>> Signed-off-by: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
>>> ---
>>> v3:
>>> - removed MHL port (samsung connector will have separate bindings),
>>> - added 2nd example for USB-C,
>>> - improved formatting
>>> v2:
>>> - moved connector type(A,B,C) to compatible string (Rob),
>>> - renamed size property to type (Rob),
>>> - changed type description to be less confusing (Laurent),
>>> - removed vendor specific compatibles (implied by graph port number),
>>> - added requirement of connector being a child of IC (Rob),
>>> - removed max-mode (subtly suggested by Rob, it should be detected anyway
>>>   by USB Controller in runtime, downside is that device is not able to
>>>   report its real capabilities, maybe better would be to make it optional(?)),
>>> - assigned port numbers to data buses (Rob).
>>>
>>> Regards
>>> Andrzej
>>>
>>> Signed-off-by: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
>>>
>>> dt-bindings: add bindings for USB physical connector v3
>>> ---
>>>  .../bindings/connector/usb-connector.txt           | 74 ++++++++++++++++++++++
>>>  1 file changed, 74 insertions(+)
>>>  create mode 100644 Documentation/devicetree/bindings/connector/usb-connector.txt
>>>
>>> diff --git a/Documentation/devicetree/bindings/connector/usb-connector.txt b/Documentation/devicetree/bindings/connector/usb-connector.txt
>>> new file mode 100644
>>> index 000000000000..1efda92639da
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/connector/usb-connector.txt
>>> @@ -0,0 +1,74 @@
>>> +USB Connector
>>> +=============
>>> +
>>> +USB connector node represents physical USB connector. It should be
>>> +a child of USB interface controller.
>>> +
>>> +Required properties:
>>> +- compatible: describes type of the connector, must be one of:
>>> +    "usb-a-connector",
>>> +    "usb-b-connector",
>>> +    "usb-c-connector".
>>> +
>>> +Optional properties:
>>> +- label: symbolic name for the connector,
>>> +- type: size of the connector, should be specified in case of USB-A, USB-B
>>> +  non-standard (large) connector sizes: "mini", "micro".
>> The smaller connectors are standard too. Perhaps "non-fullsize connector
>> sizes".
>
> The word "standard" is used in specs, but your description looks better,
> maybe even shorter version would work: "non-fullsize connectors:".

Sure.

>> We're missing a micro-AB connector, but I think those are actually
>> pretty rare. Most phones are micro-B connectors, but do both host and
>> device.
>>
>>> +
>>> +Required nodes:
>>> +- any data bus to the connector should be modeled using the OF graph bindings
>>> +  specified in bindings/graph.txt, unless the bus is between parent node and
>>> +  the connector. Since single connector can have multpile data buses every bus
>>> +  has assigned OF graph port number as follows:
>>> +    0: High Speed (HS), present in all connectors,
>>> +    1: Super Speed (SS), present in SS capable connectors,
>> This should also say endpoint 0 is USB-SS, endpoint 1 (and higher?) is
>> Alternate Mode. And show in the example.
>
> What if there is SS mux before, which muxes USB-SS and DP lines. In my
> case the mux is located in USB-PHY (it is 2nd example below).
> In such case there is only one graph connection to SS port and this
> connection will handle both USB-SS and AltMode traffic.

Ah yes, good point.

> Anyway from USB-C connector's point of view, there is no distinction
> which lines are USB-SS, which are AltMode. In fact platform decides in
> real time about muxing of SS and AltMode signals, as it depends on
> cable/plug orientations. Maybe instead of mapping endpoint numbers to
> SS/AltMode, we should map them to SS1/SS2 lines if necessary(???).
>
> To be sure of your intentions. Do you want to model simple SS muxes as a
> part of USB-C connector?

That was, but you are right. That should be part of whatever device
does the muxing.

Given you need a uC just to manage the USB-C connector, I'd guess
there isn't any simple case like just a GPIO to control a mux.

>
>>> +    2: Sideband use (SBU), present in USB-C.
>>> +
>>> +Examples
>>> +--------
>>> +
>>> +1. Micro-USB connector with HS lines routed via controller (MUIC):
>>> +
>>> +muic-max77843@66 {
>>> +    ...
>>> +    usb_con: connector {
>>> +            compatible = "usb-b-connector";
>>> +            label = "micro-USB";
>>> +            type = "micro";
>>> +    };
>>> +};
>>> +
>>> +2. USB-C connector attached to CC controller (s2mm005), HS lines routed
>>> +to companion PMIC (max77865), SS lines to USB3 PHY and SBU to DisplayPort:
>> Having SBU to DP but no DP video path connection is wrong.
>
> But it is real hardware :)
> As I said earlier, DP video lines are connected to mux in USB3-PHY.
> I can add this explanation to the description to make it clear.

Okay.

Rob