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

- From: Greg KH \<gregkh@linuxfoundation.org\>
- Date: 2021-11-06 14:41:57 
- List: linux-mediatek
- Page: https://ratatoskr.run/linux-mediatek/2021/11/1564488
- Thread: https://ratatoskr.run/linux-usb/2021/11/1559781/t.md

```text
On Fri, Nov 05, 2021 at 09:56:59PM +0200, Mathias Nyman wrote:
> On 5.11.2021 18.15, Greg KH wrote:
> > On Fri, Nov 05, 2021 at 06:00:36PM +0200, 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>
> > 
> > So this needs:
> > 	Fixes: 90d28fb53d4a ("usb: core: reduce power-on-good delay time of root hub")
> > right?
> 
> I guess so, not sure on "Fixes" policy here.
> 
> This patch fixes an xhci issue revealed by ("usb: core: reduce power-on-good delay time of root hub")
> That original patch itself looks correct, but these two patches should really go together to
> avoid any enumeration issues.  

Great, I'll use that tag for now so that it will get backported
properly.

greg k-h

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