Re: [PATCH] xhci: Fix HIK camera control timeout on Etron hosts

[Michal Pecio <michal.pecio@gmail.com>]

On Mon, 14 Sep 2026 09:30:33 +0800, Kuangyi Chiang wrote:
> Control transfers to the HIK 1080P Camera (2bdf:0280) can time out when
> the device is connected through an Etron xHCI host:
> 
> [   48.363671] uvcvideo: Found UVC 1.00 device HIK 1080P Camera (2bdf:0280)
> [   53.465662] uvcvideo: Failed to set UVC probe control : -110 (exp. 26).
> [   58.585653] uvcvideo: Failed to query (129) UVC probe control : -110 (exp. 26).
> [   58.592967] uvcvideo: Failed to initialize the device (-5).
> 
> Testing shows that at least 125 us between control transfers is required
> to avoid the timeout. Limit the workaround to the affected Etron host and
> USB device combination to avoid changing control-transfer timing for other
> devices.

Any idea why it happens or why the delay helps?
How many other HCs did you test this camera with?
Does it help to reconnect and try again?

FWIW, I tried a few USB 2.0 cameras with my Etron and they mostly work,
except one. It passes probe just fine, but fails on streaming attempt.
Adding 125us delay doesn't help, but 1000 works sometimes and 4000 even
more often.

Probably a HW bug. Honestly, I never use Etron for anything serious.

> Perform the delay before taking xhci->lock so the existing state
> validation and TD queueing remain in the same critical section. Use
> udelay() because urb_enqueue() may be called from atomic context and
> cannot use a sleeping delay.

Actually, you would need to do that under lock if you want to ensure
that multiple callers can't submit URBs closely together. But that's
dodgy and we don't even know what exactly triggers it or whether this
solution really is the best one.

Regards,
Michal