Re: [RFC PATCH v2 1/5] dt-bindings: add bindings for USB physical connector

[Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

On Mon, Feb 05, 2018 at 10:06:35AM +0100, Andrzej Hajda wrote:
> On 05.02.2018 07:08, Rob Herring wrote:
> > On Wed, Jan 31, 2018 at 02:44:31PM +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-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
> >> ---
> >> 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),
> > How so? More below...
> >
> >> - 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-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
> >> ---
> >>  .../bindings/connector/usb-connector.txt           | 48 ++++++++++++++++++++++
> >>  1 file changed, 48 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..02020f5d760a
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/connector/usb-connector.txt
> >> @@ -0,0 +1,48 @@
> >> +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",
> > Nit: one per line.
> >
> >> +
> >> +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"
> >> +
> >> +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,
> >> +    2: Sideband use (SBU), present in USB-C,
> >> +    3: Mobile High-Definition Link (MHL), present in 11-pin Samsung micro-USB
> > This is un-muxed unlike Type-C where the signals are muxed with USB SS. 
> > That makes me think the Samsung connector should have its own compatible 
> > string.
> 
> Do you mean, sth like:
>     connector {
>             compatible = "samsung,usb-connector-11pin";
>             label = "micro-USB";
>             ports {
>                     #address-cells = <1>;
>                     #size-cells = <0>;
> 
>                     port@3 {
>                             reg = <3>;
>                             musb_con_mhl_in: endpoint {
>                                     remote-endpoint = <&mhl_out>;
>                             };
>                     };
>     };

Yes, basically.

> 
> Or should I add "usb-b-connector" extra compatible and "type" property?

type would be micro? I think type and "usb-b-connector" are fine if this 
is a superset like a USB3 SS micro connector.

> I slightly prefer my approach(less different bindings), but I am also OK
> with the above.

How do you know it is a Samsung connector then? Just because you have 
port 3? I think it is better to be explicit.

> 
> >
> > Can we go ahead and define the video modes of Type-C? Normally, if 2 
> > data streams are mutually exclusive, then they are a single port with 2 
> > endpoints. So we'd either have 2 endpoints on port 1 or we stick with 
> > port 3 is always video. We can still know what is mutually exclusive 
> > based on the compatible. 
> 
> I am sorry, I do not understand what you mean. Port 3 is present only in
> 11-pin Samsung micro-USB, USB Type-C has only ports 0, 1, 2.

So video on Type C would be on port 1 (SS), endpoint ? ? That's not 
defined in the binding and I want to define it.

> Here is list of possible ports depending on connector type:
> - USB 2.0: HS
> - 11-pin Samsung micro-USB: HS,MHL
> - USB 3.x type A,B: HS,SS
> - USB-C: HS,SS,SBU
> 
> All ports have separate lines, so they can work simultaneously.
> 
> And regarding MHL on standard micro-USB connector. MHL and MUIC will
> share HS port, but there will be mux somewhere before connector:

That's another case I hadn't considered. I was mainly thinking just how 
to handle Type C.

> - in MUIC, in this case MUIC will be the parent of the connector, and
> there will be graph from MHL to MUIC to describe MHL link,
> - in MHL, in this case MHL will be the parent of the connector, and
> graph between MUIC and MHL to describe HS link,
> - dedicated mux to MUIC and MHL, controlled by gpio pin, it could be
> handled by MUIC's external-mux gpio property for example, or (probably)
> less hacky by separate node for mux,
> or as additional property in the connector (who should be the parent of
> the connector then? Probably MUIC?).
> 
> Regards
> Andrzej
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