linux-kernel - Re: [PATCH v2] xhci: reduce xhci_handshake timeout in xhci

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Date:   Wed, 16 Feb 2022 17:58:15 +0200
From:   Mathias Nyman <mathias.nyman@...ux.intel.com>
To:     Pavan Kondeti <quic_pkondeti@...cinc.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        quic_ugoswami@...cinc.com, Jung Daehwan <dh10.jung@...sung.com>,
        Sergey Shtylyov <s.shtylyov@....ru>
Subject: Re: [PATCH v2] xhci: reduce xhci_handshake timeout in xhci_reset

On 15.2.2022 19.07, Pavan Kondeti wrote:
>>>>
>>>> The crash reports I have seen are pointing to
>>>>
>>>> usb_remove_hcd()->xhci_stop()->xhci_reset()
>>>
>>> Ok, so xhci_stop() and xhci_shutdown() both may call xhci_reset() with interrupts
>>> disabled and spinlock held. In both these cases we're not that interested in the
>>> outcome of xhci_reset().
>>>
>>> But during probe we call xhci_reset() with interrupts enabled without spinlock,
>>> and here we really care about it succeeding.
>>> I'm also guessing reset could take a longer time during probe due to possible recent
>>> BIOS handover, or firmware loading etc.
>>>
>>> So how about passing a timeout value to xhci_reset()?
>>> Give it 10 seconds during probe, and 250ms in the other cases.
>>>
>>
>> Thanks for this suggestion.
>>
>> This sounds better compared to the quirks approach. xhci_resume() also seems
>> to be calling xhci_reset() in the hibernation path, I believe we should treat
>> this like probe()/startup case and give larger timeout.
>>
> I will test the below patch as per Mathias suggestion.
> 
> Thanks,
> Pavan
> 
> diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
> index df3522d..031fe90 100644
> --- a/drivers/usb/host/xhci-hub.c
> +++ b/drivers/usb/host/xhci-hub.c
> @@ -762,7 +762,7 @@ static int xhci_exit_test_mode(struct xhci_hcd *xhci)
>  	}
>  	pm_runtime_allow(xhci_to_hcd(xhci)->self.controller);
>  	xhci->test_mode = 0;
> -	return xhci_reset(xhci);
> +	return xhci_reset(xhci, false);

Maybe just pass the timeout value directly to xhci_reset().
Looks like readl_poll_timeout_atomic() uses u64 for timeout_us,
makes sense to use the same.

Sergey also pointed out xhci_handshake() incorrectly uses a signed integer for timeouts.
This could be changed to u64 as well.

I'll write a patch that does all above

-Mathias