Hi
On 4.4.2022 19.38, Luke Nowakowski-Krijger wrote:
> Hello,
>
> There have been some users using Ubuntu 5.4 based kernels with certain intel xHCI controllers that are experiencing USB devices not being detected during boot [4][5].
> This problem seems to have been reintroduced after the patchset that deferred primary roothub registration to address device enumeration before
> xHC is running was reverted due to regressions [1][2].
>
> My question is if there has been any efforts to reintroduce these patches or any other fixes that I am not aware of to address the original problem [3]?
Not yet, thanks for the reminder.
> There seem to have been many bug fixes addressing the problems referenced in the original regression report [2] to do with this patch series,
> is there anything in the way of reintroducing these patches? From only looking at the mailing list discussions and various bug reports, I still am not exactly
> sure what the problems with these patches were in the first place.>
> Anyways, these things seem pretty tricky and I would appreciate any insight on the matter :)
The race issues those patches exposed should be fixed by now, so I think we should
try to add those patches again.
My understanding is that the patch [1] reducing root hub power-on-good delay in 5.13-rc1
revealed a enumeration issue due to roothub being active before host is running.
In 5.15-rc3 two patches [2], [3] were added to defer roothub registration.
This exposed a race when both roothubs were added at the same time, causing
regression and more enumeration issues, so patches [2] and [3] were reverted in 5.16-rc1.
The race issues were then later fixed in 5.16-rc3 with patches [4] and [5]
[1] 90d28fb53d4a ("usb: core: reduce power-on-good delay time of root hub"). 5.13-rc1
[2] b7a0a792f864 ("xhci: Set HCD flag to defer primary roothub registration") 5.15-rc3
[3] 58877b0824da ("usb: core: hcd: Add support for deferring roothub registration") 5.15-rc3
[4] 6ae6dc22d2d1 ("usb: hub: Fix usb enumeration issue due to address0 race") 5.16-rc3
[5] 6cca13de26ee ("usb: hub: Fix locking issues with address0_mutex") 5.16-rc3
-Mathias
