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    SubjectRe: debugging oops after disconnecting Nexio USB touchscreen
    On Fri, 4 Dec 2009, Ondrej Zary wrote:

    > [ 3.712039] usb 2-1: new full speed USB device using uhci_hcd and address 2
    > [ 3.726791] kjournald starting. Commit interval 5 seconds
    > [ 3.726817] EXT3-fs (sda2): mounted filesystem with ordered data mode
    > [ 3.851384] usb 2-1: not running at top speed; connect to a high speed hub
    > [ 3.859379] usb 2-1: New USB device found, idVendor=2001, idProduct=f103
    > [ 3.859387] usb 2-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
    > [ 3.862635] hub 2-1:1.0: USB hub found
    > [ 3.864385] hub 2-1:1.0: 7 ports detected

    That's the problem. Notice the "not running at top speed" message?
    Something went wrong when the hub was detected. It could be a problem
    in your EHCI controller or a problem in the hub.

    You can get more information about this by unplugging the hub, running
    usbmon (on the 0u file), and then plugging the hub back in.


    > diff between ehci and uhci logs:
    > There seems to be some problem with timing.
    > Also order of ehci_usb vs uhci_usb loading changes.

    That order doesn't matter much. But this...

    > --- dmesg-ehci.txt- 2009-12-04 20:01:39.000000000 +0100
    > +++ dmesg-uhci.txt- 2009-12-04 20:01:31.000000000 +0100
    > @@ -144,10 +144,9 @@
    > Console: colour VGA+ 80x25
    > console [tty0] enabled
    > hpet clockevent registered
    > - Fast TSC calibration failed
    > - TSC: PIT calibration matches HPET. 1 loops
    > - Detected 1608.000 MHz processor.
    > - Calibrating delay loop (skipped), value calculated using timer frequency.. 3216.00 BogoMIPS (lpj=6432000)
    > + Fast TSC calibration using PIT
    > + Detected 1608.123 MHz processor.
    > + Calibrating delay loop (skipped), value calculated using timer frequency.. 3216.24 BogoMIPS (lpj=6432492)
    > Security Framework initialized
    > SELinux: Disabled at boot.
    > Mount-cache hash table entries: 512
    > @@ -180,7 +179,7 @@
    > CPU1: Thermal monitoring enabled (TM2)
    > CPU1: Intel(R) Atom(TM) CPU N270 @ 1.60GHz stepping 02
    > Brought up 2 CPUs
    > - Total of 2 processors activated (9326.27 BogoMIPS).
    > + Total of 2 processors activated (6432.20 BogoMIPS).

    Those two differences seem strange to me. You might want to report it
    in a new email thread on LKML. You might also want to see if the same
    thing happens with a 2.6.32 kernel.

    > > This may be a bug in ehci-hcd, a bug in your EHCI hardware, or a bug in
    > > the hub. Can you try using a different high-speed hub to see if it
    > > makes any difference?
    >
    > Yes, I'll try it next week (I have only remote access now).
    > I have different 7-port hub available to test (should be with Philips chipset).

    It's worth a try. Still, the original problem you saw (the oops in
    ehci-hcd) is in software, not in hardware, so the hub can't be entirely
    responsible.

    Alan Stern



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