linux-kernel - Re: debugging oops after disconnecting Nexio USB touchscreen

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Date:	Fri, 4 Dec 2009 16:24:25 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Ondrej Zary <linux@...nbow-software.org>
cc:	linux-usb@...r.kernel.org, <linux-kernel@...r.kernel.org>
Subject: Re: 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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