[LAU] USB on ThinkPad T520

plutek plutek at infinity.net
Sun May 13 18:32:18 UTC 2012

From: Robin Gareus <robin at gareus.org>
Date: Sun, 13 May 2012 20:15:49 +0200

> 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`

yeah... nothing.

> 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.

well, when i do that, this happens:

rmmod ehci_hcd
(lsmod shows neither ehci nor uhci)

modprobe uhci_hcd
(lsmod shows BOTH ehci and uhci)

rmmod uhci_hcd
(lsmod shows only ehci)
(USB devices don't appear in qjackctl)

i.e., it seems like USB devices show ONLY when ehci is loaded.

> 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."

yeah, i'm starting to play with more recent kernels.... so far nothing does any better!  :-(


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