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

[Michal Pecio]

On Thu, 29 Oct 2026 10:25:17 +0800, Kuangyi Chiang wrote:
> We did some more testing.
> 
> We don't see this issue during device enumeration.
> 
> We also found that the timeout is not limited to UVC control
> transfers. In one failure case, the first timeout was observed in
> a UAC control transfer, followed by UVC control transfer timeouts:
> 
> [  961.127402] usb 2-3: 5:2: failed to get current value for ch 0 (-110)
> [  971.367443] uvcvideo 2-3:1.0: Failed to query (GET_DEF) UVC control
> 2 on unit 2: -110 (exp. 2).
> [  976.487473] uvcvideo 2-3:1.0: Failed to query (GET_DEF) UVC control
> 3 on unit 2: -110 (exp. 2).

But that's the same device and the same control pipe, right?

So it just failed and we don't know why or whether it was the host or
the device. And this is all during UVC/UAC probe, before any userspace
begins using the device? Or could userspace be involved?

The UVC driver has some aggressive PM; for every userspace ioctl, it
calls usb_autopm_get_interface(), submits an interrupt URB which almost
never completes and unlinks the URB before usb_autopm_put_interface().
Repeated periodic unlinks is a known problem case for many xHCI chips.

FYI, I found that 7c0c31c66a7f9 in v7.3 reduced occurrences of periodic
unlink failures on other junk HW like ASMedia and VIA. Some of those
failures, on ASMedia, resulted in control transfer breakage too.

Have you tried 7.3 yet?
Do you see any interrupt URBs there, using usbmon for example?

> So far, we have reproduced the issue with these xHCI hosts:
> 
> ASMedia ASM1142 (1b21:1242)
> Etron EJ168 (1b6f:7023)
> Etron EJ188 (1b6f:7052)
> Intel xHCI (8086:8d31)

I don't know that Intel chip, but the others are quite buggy.

Have you tried other HCs? Any successes?
IME, chips from NEC, Fresco, Renesas are more reliable.

> The camera works with the EHCI host we tested without any additional
> delay.

That's a little suspicious, it may still be an xHCI bug.

Regards,
Michal