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

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Message-ID: <20220217030343.GA32039@hu-pkondeti-hyd.qualcomm.com>
Date:   Thu, 17 Feb 2022 08:33:43 +0530
From:   Pavan Kondeti <quic_pkondeti@...cinc.com>
To:     Mathias Nyman <mathias.nyman@...ux.intel.com>
CC:     Pavan Kondeti <quic_pkondeti@...cinc.com>,
        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

Hi Mathias,

On Wed, Feb 16, 2022 at 05:58:15PM +0200, Mathias Nyman wrote:
> 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
> 
Thank you. I will look forward to your patch and provide the test results with
it.

Thanks,
Pavan