linux-kernel - Re: [PATCH v2] dt-bindings: usb: Add binding for Microchip usb5744 hub controller

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Date:   Tue, 9 May 2023 18:04:00 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Michal Simek <michal.simek@....com>, linux-kernel@...r.kernel.org,
        monstr@...str.eu, michal.simek@...inx.com, git@...inx.com,
        ilias.apalodimas@...aro.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Piyush Mehta <piyush.mehta@....com>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-usb@...r.kernel.org
Subject: Re: [PATCH v2] dt-bindings: usb: Add binding for Microchip usb5744
 hub controller

On 09/05/2023 16:19, Michal Simek wrote:
> 
> 
> On 5/7/23 10:07, Krzysztof Kozlowski wrote:
>> On 05/05/2023 15:25, Michal Simek wrote:
>>> The Microchip usb5744 is a SS/HS USB 3.0 hub controller with 4 ports.
>>> The binding describes USB related aspects of the USB5744 hub, it as
>>> well cover the option of connecting the controller as an i2c slave.
>>> When i2c interface is connected hub needs to be initialized first.
>>> Hub itself has fixed i2c address 0x2D but hardcoding address is not good
>>> idea because address can be shifted by i2c address translator in the
>>> middle.
>>>
>>> Signed-off-by: Piyush Mehta <piyush.mehta@....com>
>>> Signed-off-by: Michal Simek <michal.simek@....com>
>>> ---
>>>
>>> Changes in v2:
>>> - fix i2c-bus property
>>> - swap usb2.0/3.0 compatible strings
>>> - fix indentation in example (4 spaces)
>>> - add new i2c node with microchip,usb5744 compatible property
>>>
>>> It looks like that usb8041 has also an optional i2c interface which is not
>>> covered. But it is mentioned at commit 40e58a8a7ca6 ("dt-bindings: usb:
>>> Add binding for TI USB8041 hub controller").
>>>
>>> i2c-bus name property was suggested by Rob at
>>> https://lore.kernel.org/all/CAL_JsqJedhX6typpUKbnzV7CLK6UZVjq3CyG9iY_j5DLPqvVdw@mail.gmail.com/
>>> and
>>> https://lore.kernel.org/all/CAL_JsqJZBbu+UXqUNdZwg-uv0PAsNg55026PTwhKr5wQtxCjVQ@mail.gmail.com/
>>>
>>> the question is if adding address like this is acceptable.
>>> But it must be specified.
>>>
>>> Driver will follow based on final dt-binding.
>>>
>>> $ref: usb-device.yaml# should be also added but have no idea how to wire it
>>> up to be applied only on usb node not i2c one.
>>>
>>> ---
>>>   .../bindings/usb/microchip,usb5744.yaml       | 110 ++++++++++++++++++
>>>   1 file changed, 110 insertions(+)
>>>   create mode 100644 Documentation/devicetree/bindings/usb/microchip,usb5744.yaml
>>>
>>> diff --git a/Documentation/devicetree/bindings/usb/microchip,usb5744.yaml b/Documentation/devicetree/bindings/usb/microchip,usb5744.yaml
>>> new file mode 100644
>>> index 000000000000..7e0a3472ea95
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/usb/microchip,usb5744.yaml
>>> @@ -0,0 +1,110 @@
>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>> +%YAML 1.2
>>> +---
>>> +$id: http://devicetree.org/schemas/usb/microchip,usb5744.yaml#
>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>> +
>>> +title: Microchip USB5744 4-port Hub Controller
>>> +
>>> +description:
>>> +  Microchip's USB5744 SmartHubTM IC is a 4 port, SuperSpeed (SS)/Hi-Speed (HS),
>>> +  low power, low pin count configurable and fully compliant with the USB 3.1
>>> +  Gen 1 specification. The USB5744 also supports Full Speed (FS) and Low Speed
>>> +  (LS) USB signaling, offering complete coverage of all defined USB operating
>>> +  speeds. The new SuperSpeed hubs operate in parallel with the USB 2.0
>>> +  controller, so 5 Gbps SuperSpeed data transfers are not affected by slower
>>> +  USB 2.0 traffic.
>>> +
>>> +maintainers:
>>> +  - Piyush Mehta <piyush.mehta@....com>
>>> +  - Michal Simek <michal.simek@....com>
>>> +
>>> +select:
>>> +  properties:
>>> +    compatible:
>>> +      contains:
>>> +        const: microchip,usb5744
>>> +  required:
>>> +    - compatible
>>
>> I don't understand why do you need this select. It basically disables
>> schema matching for other ones.
> 
> I didn't find a way how to have usbXXX,XXXX compatible strings and 
> microchip,usb5744 compatible in the same file. I am definitely lacking knowledge 
> how to write it properly that's why any advise is welcome.

Hm, if you just have both of them like you have now, what happens?

Best regards,
Krzysztof