# Re: \[PATCH\] xhci: Fix USB 3.1 enumeration issues by increasing roothub power-on-good delay

- From: Walt Jr. Brake \<hidden\>
- Date: 2021-11-05 17:32:46 
- List: linux-arm-kernel
- Page: https://ratatoskr.run/linux-arm-kernel/2021/11/1564119
- Thread: https://ratatoskr.run/linux-usb/2021/11/1559781/t.md

```text
On 6/11/2021 00:09, Mathias Nyman wrote:
> On 5.11.2021 18.00, Mathias Nyman wrote:
>> Some USB 3.1 enumeration issues were reported after the hub driver removed
>> the minimum 100ms limit for the power-on-good delay.
>>
>> Since commit 90d28fb53d4a ("usb: core: reduce power-on-good delay time of
>> root hub") the hub driver sets the power-on-delay based on the
>> bPwrOn2PwrGood value in the hub descriptor.
>>
>> xhci driver has a 20ms bPwrOn2PwrGood value for both roothubs based
>> on xhci spec section 5.4.8, but it's clearly not enough for the
>> USB 3.1 devices, causing enumeration issues.
>>
>> Tests indicate full 100ms delay is needed.
>>
>> Reported-by: Walt Jr. Brake <redacted>
>> Signed-off-by: Mathias Nyman <redacted>
>>
> Walt Jr Brake, just to be sure could you test this one as well?
>
> As Alan suggested this sets 100ms for the USB 3 roothub but
> keeps the 20ms for the USB 2 roothub.
>
> Thanks
> -Mathias

Yes I tested, it works too.


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