Re: [PATCH v5 1/6] dt-bindings: add bindings for USB physical connector

From: Andrzej Hajda <a.hajda@samsung.com>
To: Roger Quadros <rogerq@ti.com>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
	<devicetree@vger.kernel.org>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	dri-devel@lists.freedesktop.org, Inki Dae <inki.dae@samsung.com>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Krzysztof Kozlowski <krzk@kernel.org>,
	Chanwoo Choi <cw00.choi@samsung.com>,
	Archit Taneja <architt@codeaurora.org>,
	Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-samsung-soc@vger.kernel.org, linux-usb@vger.kernel.org
Subject: Re: [PATCH v5 1/6] dt-bindings: add bindings for USB physical connector
Date: Mon, 12 Mar 2018 08:02:54 +0100	[thread overview]
Message-ID: <b588527d-2ca2-9e88-9e27-e09e5b52f8d6@samsung.com> (raw)
In-Reply-To: <ed0ce43c-3c81-b027-2eb1-30e49156c3ac@ti.com>

On 09.03.2018 11:24, Roger Quadros wrote:
> Hi,
>
> On 27/02/18 09:11, 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@samsung.com>
>> ---
>> v4:
>> - improved 'type' description (Rob),
>> - improved description of 2nd example (Rob).
>> 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
>> ---
>>  .../bindings/connector/usb-connector.txt           | 75 ++++++++++++++++++++++
>>  1 file changed, 75 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..e1463f14af38
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/connector/usb-connector.txt
>> @@ -0,0 +1,75 @@
>> +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".
> compatible should be just "usb-connector"
>
> Type should be a property
>
> type: type of usb connector "A", "B", "AB", "C"
> AB is for dual-role connectors.

I have proposed such property (and size also) in my first RFC [1]. Rod
did not like it :)

[1]: https://marc.info/?l=devicetree&m=150660411515233&w=2

>
> micro super-speed and high-speed connectors are different. How do you differentiate that?

I am aware of it, and property differentiating it was also in my earlier
iterations.
If there will be need to differentiate such connectors, adding property
max-speed or max-mode would do the thing.

>
>> +
>> +Optional properties:
>> +- label: symbolic name for the connector,
> Why do you need label? We can't maintain consistency as people will put creative names there.
> Device/bus driver could generate a valid label.

It follows convention for other connectors: HDMI, DVI, ....

>
>> +- type: size of the connector, should be specified in case of USB-A, USB-B
>> +  non-fullsize connectors: "mini", "micro".
> type is misleading. Type is usually A/B/C. It should be size here instead.

As you can see in discussion for previous iterations it follows
convention already established for other connectors.

>
> size: size of the connector if not standard size. "mini", "micro"
>
> If not specified it is treated as standard sized connector.
> e.g. for Type-C there is no mini/micro. so size doesn't have to be specificed
Few lines above it is described: should be specified in case of USB-A,
USB-B non-fullsize connectors.

>
> What about Type-C connector?
>> +
>> +Required nodes:
>> +- any data bus to the connector should be modeled using the OF graph bindings
> s/modeled/modelled

>> +  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
> s/multpile/multiple

OK, I will fix both typos.

>
>> +  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.
>> +
>> +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.
>> +DisplayPort video lines are routed to the connector via SS mux in USB3 PHY.
>> +
>> +ccic: s2mm005@33 {
>> +	...
>> +	usb_con: connector {
>> +		compatible = "usb-c-connector";
>> +		label = "USB-C";
> The label is not consistent with the earlier example.

Why?

Regards
Andrzej

>
>> +
>> +		ports {
>> +			#address-cells = <1>;
>> +			#size-cells = <0>;
>> +
>> +			port@0 {
>> +				reg = <0>;
>> +				usb_con_hs: endpoint {
>> +					remote-endpoint = <&max77865_usbc_hs>;
>> +				};
>> +			};
>> +			port@1 {
>> +				reg = <1>;
>> +				usb_con_ss: endpoint {
>> +					remote-endpoint = <&usbdrd_phy_ss>;
>> +				};
>> +			};
>> +			port@2 {
>> +				reg = <2>;
>> +				usb_con_sbu: endpoint {
>> +					remote-endpoint = <&dp_aux>;
>> +				};
>> +			};
>> +		};
>> +	};
>> +};
>>