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

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Date:   Tue, 9 May 2023 16:19:45 +0200
From:   Michal Simek <michal.simek@....com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        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 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.

Thanks,
Michal