[PATCH v11 3/7] usb: onboard-hub: add support for Microchip USB5744

[Marek Vasut]

On 11/19/24 4:22 AM, Abbarapu, Venkatesh wrote:

[...]

>>>>>> Is there a matching delay requirement specified in the USB hub
>>>>>> datasheet or is this a workaround for some board-specific behavior ?
>>>>> The matching delay is not specified in the USB5744 hub document, but
>>>>> based on
>>>> testing on 2 boards with the above-mentioned delay i2c failures were not
>> observed.
>>>> Is this 10ms a board-specific reset delay ?
>>>> Why is it in a generic driver ?
>>> On our boards we observed i2c failures when we set the reset delay as
>>> 5us and power on delay as 1ms as per the USB5744 datasheet. The reason
>>> of adding 10ms delay is because of i2c failures and the linux
>>> reference is
>>> https://github.com/torvalds/linux/commit/908f61bedb2c40c6d856bbfd7f870
>>> b967a4cb498 Do you have anything with respect to these delays, as you
>>> might have tested on some other boards? If anything, please let me know.
>> If the 10ms delay is a board specific delay, then this has to be handled in a board
>> specific way, not hard-coded in the driver. Probably add some new property which
>> specifies the extra board specific reset delay, but be sure to run that property by the
>> Linux kernel maintainers too.
> Thanks. I will check how to add the board specific delay as new property.

Add some reset-...-us , similar to what ethernet PHYs already do in DT.

> As this delay might be specific to the boards which we tested.
> There won't be any issue if we can add the default "reset_delay"(5us) and "power_on_delay" (1ms) from the USB5744 datasheet, as other boards will be working without any board specific delay?
Right, the driver has to be generic , that means it should contain 
delays specified in the datasheet. Board specific delays have to be 
configured in board specific DTs.