Re: xHCI problem? [was Re: Erratic USB device behavior and device loss]

Alan Stern
2016-09-21T14:37:39Z

On Wed, 21 Sep 2016, Ritesh Raj Sarraf wrote:

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> Hi Alan,
>
> On Tue, 2016-09-20 at 10:16 -0400, Alan Stern wrote:
> > This is a lot better.  No more I/O errors.
> >
> > We still have irregular suspends and resumes, but that's to be
> > expected.  More worrying are the spontaneous disconnects.  They don't
> > seem to be related to the suspend/resume activity.
> >
> > You can disable suspend for this device entirely by doing:
> >
> >         echo on >/sys/bus/usb/devices/2-4/power/control
> >
> > I'm afraid that this won't prevent the device from disconnecting
> > itself, though.  This appears to be some sort of hardware bug that
> > can't be fixed in software.
>
> I'm not sure what you were referring to when you said "No more I/O errors".

I was referring to the attempts at I/O while the device was suspended.
They didn't occur in your most recent test.

> But I still got these errors today, with all patches applied.
>
> Sep 21 14:58:11 learner kernel: usb 2-4: new high-speed USB device number 98
> using xhci_hcd
> Sep 21 14:58:18 learner kernel: usb 2-4: new high-speed USB device number 102
> using xhci_hcd
> Sep 21 14:58:24 learner kernel: usb 2-4: new high-speed USB device number 106
> using xhci_hcd
> Sep 21 14:58:31 learner kernel: usb 2-4: new high-speed USB device number 114
> using xhci_hcd
> Sep 21 14:58:41 learner kernel: usb 2-4: new high-speed USB device number 12
> using xhci_hcd
> Sep 21 14:58:41 learner kernel: usb 2-4: device descriptor read/64, error -71
> Sep 21 14:58:41 learner kernel: usb 2-4: device descriptor read/64, error -71
> Sep 21 14:58:41 learner kernel: usb 2-4: new high-speed USB device number 13
> using xhci_hcd

These are a completely different kind of error. They occurred during a
reset, which followed one of those spontaneous disconnects. Probably
the cause of the disconnect is also the cause of these errors.

Alan Stern