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

- From: Mathias Nyman \<hidden\>
- Date: 2021-11-05 19:40:04 
- List: linux-usb
- Page: https://ratatoskr.run/linux-usb/2021/11/1564193
- Thread: https://ratatoskr.run/linux-usb/2021/11/1559781/t.md

```text
On 5.11.2021 19.32, Walt Jr. Brake wrote:
> 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.
> 

Thank you
-Mathias
```