linux-kernel - Re: usb: host: Reduce xhci_handshake timeout in xhci

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Message-ID: <20220211074331.GA12625@hu-pkondeti-hyd.qualcomm.com>
Date:   Fri, 11 Feb 2022 13:13:31 +0530
From:   Pavan Kondeti <quic_pkondeti@...cinc.com>
To:     Pavan Kondeti <quic_pkondeti@...cinc.com>
CC:     Mathias Nyman <mathias.nyman@...el.com>,
        Jung Daehwan <dh10.jung@...sung.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <quic_ugoswami@...cinc.com>
Subject: Re: usb: host: Reduce xhci_handshake timeout in xhci_reset

Sorry for the spam. I have added an incorrect email address in my previous
email.

On Fri, Feb 11, 2022 at 12:16:30PM +0530, Pavan Kondeti wrote:
> On Mon, Jun 28, 2021 at 10:49:00AM +0300, Mathias Nyman wrote:
> > On 28.6.2021 9.55, Jung Daehwan wrote:
> > > On Mon, Jun 28, 2021 at 08:53:02AM +0200, Greg Kroah-Hartman wrote:
> > >> On Mon, Jun 28, 2021 at 11:25:48AM +0900, Jung Daehwan wrote:
> > >>> On Tue, Jun 22, 2021 at 09:56:20PM +0200, Greg Kroah-Hartman wrote:
> > >>>> On Tue, Jun 22, 2021 at 08:24:56PM +0900, Daehwan Jung wrote:
> > >>>>> It seems 10 secs timeout is too long in general case. A core would wait for
> > >>>>> 10 secs without doing other task and it can be happended on every device.
> > >>>>
> > >>>> Only if the handshake does not come back sooner, right?
> > >>>
> > >>> Yes, right.
> > >>>
> > >>>> What is causing your device to timeout here?
> > >>>
> > >>> Host Controller doesn't respond handshake. I don't know why and I ask HW team
> > >>> to debug it.
> > >>
> > >> Please work to fix your hardware, that feels like the root of the
> > >> problem here.  If you require the timeout for xhci_reset() to happen,
> > >> then how do you know that the hardware really did reset properly in the
> > >> reduced amount of time you just provided?
> > >>
> > > 
> > > I continue fixing this issue with hardware engineer, but currently just
> > > host controller can crash whole system and that's why I want to fix it.
> > > How about adding some error logs in this situation for recognizing this issue?
> > > We can add error log in xhci_stop as xhci_reset can returns error like below.
> > > 
> > > static void xhci_stop(struct usb_hcd *hcd)
> > > {
> > >         u32 temp;
> > >         struct xhci_hcd *xhci = hcd_to_xhci(hcd);
> > > +       int ret;
> > > 
> > >         mutex_lock(&xhci->mutex);
> > > 
> > > @@ -733,6 +734,9 @@ static void xhci_stop(struct usb_hcd *hcd)
> > >         xhci->cmd_ring_state = CMD_RING_STATE_STOPPED;
> > >         xhci_halt(xhci);
> > >         xhci_reset(xhci);
> > > +       if (ret)
> > > +               xhci_err(xhci, "%s: Error while reset xhci Host controller - ret = %d\n"
> > > +                       , __func__, ret);
> > >         spin_unlock_irq(&xhci->lock);
> > > 
> > 
> > We can check the xhci_reset() return value here and print a message, makes sense.
> > 
> > The original reason for the 10 second timeout was because a host actually took 9 seconds:
> > 
> > commit 22ceac191211cf6688b1bf6ecd93c8b6bf80ed9b
> > 
> >     xhci: Increase reset timeout for Renesas 720201 host.
> >     
> >     The NEC/Renesas 720201 xHCI host controller does not complete its reset
> >     within 250 milliseconds.  In fact, it takes about 9 seconds to reset the
> >     host controller, and 1 second for the host to be ready for doorbell
> >     rings.  Extend the reset and CNR polling timeout to 10 seconds each.
> > 
> Agreed.
> 
> We also run into the similar issue (very very rarely reproduced) on
> our platforms like SM8450. The issue happens when host mode is de-activated
> (type-c cable disconnected). Since xhci_reset() is called with interrupts
> disabled, a timeout of 10 seconds is fatal to the system.
> 
> Thanks,
> Pavan