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

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Date:   Thu, 4 May 2023 09:25:44 +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] dt-bindings: usb: Add binding for Microchip usb5744 hub
 controller



On 5/4/23 08:46, Krzysztof Kozlowski wrote:
> On 03/05/2023 15:39, 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>
>> ---
>>
>> 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.
> 
> Why? phandle points it explicitly.

Ok it means just list usb hub on i2c with label and point to it. Works for me.

Thanks,
Michal