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

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Message-ID: <f298147d-a5bc-754e-a1a2-0e37b6179b53@omp.ru>
Date:   Wed, 16 Feb 2022 19:44:59 +0300
From:   Sergey Shtylyov <s.shtylyov@....ru>
To:     Mathias Nyman <mathias.nyman@...ux.intel.com>,
        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>
Subject: Re: [PATCH v2] xhci: reduce xhci_handshake timeout in xhci_reset

On 2/16/22 6:58 PM, Mathias Nyman 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

   You mean I don't need to respin my xhci_handshake() patch?
   I'm happy to do that if that's a prevailing opinion. :-)

> -Mathias

MBR, Sergey