[LAU] USB on ThinkPad T520

Robin Gareus robin at gareus.org
Sun May 13 18:15:49 UTC 2012

On 05/13/2012 07:45 PM, plutek wrote:
> From: Robin Gareus <robin at gareus.org>
> Date: Sun, 13 May 2012 08:57:26 +0200
>> On 05/13/2012 03:13 AM, plutek wrote:
>>> From: Karsten Wiese <fzuuzf at googlemail.com>
>>> Date: Sat, 12 May 2012 23:18:22 +0200
>>>> 2012/5/12 Clemens Ladisch <clemens at ladisch.de>:
>>>>> plutek wrote:
>>>>>> i've been running AVLinux5.0.3 on a ThinkPad T61p for a while now....
>>>>>> with an ART USB Dual Tube Pre, i can run Jack at 64 frames, 2 periods
>>>>>> now i've got a new ThinkPad T520, and if i start jack on USB at 64*2
>>>>>> i get hundreds of xruns in seconds.
>>>>> Both machines run (I assume) the same software?  Then the problem is
>>>>> with the hardware, or its drivers.
>>>>> Please show the output of lspci and the contents of /proc/interrupts.
>>>> Thinkwiki says its got a QM67. That does USB 1.1 via the "Rate
>>>> matching hub" and EHCI.
>>>> I guess linux's hub driver is the culprit.
>>> hmmmm.... shame.... lenovo specs said, of course, "USB 2.0".
>>> mrph.
>>> any way around this currently?
>> yes,
>> http://lists.linuxaudio.org/pipermail/linux-audio-dev/2010-October/029511.html
> after i do:
> # cd /sys/bus/pci/drivers/ehci_hcd/
> # echo -n 0000:00:1d.0 > unbind
> ...the USB audio device no longer shows up in qjackctl.
> did i misunderstand?

No, not that I can tell. "0000:00:1d.0" is the USB hub/controller, right?

The idea is to use the uhci_hcd (USB1) driver instead of ehci_hcd
(USB2). -- Maybe the module is not loaded?

 `lsmod | grep  uhci_hcd`
 `ls /sys/bus/pci/drivers/uhci_hcd/`

If they're modules: `rmmod ehci_hcd; modprobe uhci_hcd`; that'll force
all USB ports into 1.X mode; may be worth a try before playing with
dedicated per port bindings.

Anyway, there might be something else going on: as both Karsten and
Clemens noted, these "Intel Corporation Cougar Point [..] controllers
use a different driver" and "There have been fixes recently.  Try
updating the kernel."


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