Re: [PATCH v2 1/2] xhci: Add a quirk for full reset on removal

[Michał Pecio]

On Thu, 15 May 2025 23:42:50 +0000, Thinh Nguyen wrote:
> In any case, this is basically a revert of this change:
> 6ccb83d6c497 ("usb: xhci: Implement xhci_handshake_check_state()
> helper")
> 
> Can't we just revert or fix the above patch that causes a regression?

Also note that 6ccb83d6c497 claimed to fix actual problems, so
disabling it on selected hardware could bring the old bug back:

> In some situations where xhci removal happens parallel to
> xhci_handshake, we encounter a scenario where the xhci_handshake
> can't succeed, and it polls until timeout.
> 
> If xhci_handshake runs until timeout it can on some platforms result
> in a long wait which might lead to a watchdog timeout.

But on the other hand, xhci_handshake() has long timeouts because
the handshakes themselves can take a surprisingly long time (and
sometimes still succeed), so any reliance on handshake completing
before timeout is frankly a bug in itself.

Regards,
Michal