[linux-audio-user] USB audio interface issues

Hi and sorry for cross posting,

I sent this to jack-dev but it must be OT perhaps someone here will be
able to shed some light.

I'm working to get my edirol UA-25 working with ridiculously low
latency :)

jackd -R -dalsa -dhw:1 -p64 -n8

thus far I'm having some success (thanks essej) but a few hurdles
remain.

Here's the details:

Dell inspiron 5100
kernel 2.6.12-rc1-RT-V0.7.41-00 (and various other kernels from 2.6.8.1
up through 2.6.12-rc1 all with Ingo Molnar's RP patches applied)
Intel(R) Pentium(R) 4 CPU 2.40GHz
648mb ram
gentoo
recent CVS jackd

I'm able to get -p 64 -n 8 to run relatively reliably with most apps,
however when creating a new session in ardour I get an error message
like:

too many consecutive interrupt delays ... engine pausing
cycle execution failure, exiting
DRIVER NT: could not run driver cycle
16:41:41.902 XRUN callback (1).
16:41:41.902 XRUN callback (2).
16:41:41.909 Shutdown notification.
16:41:41.913 Client deactivated.
16:41:41.915 JACK is stopping...
zombified - calling shutdown handler
delay of 16535.000 usecs exceeds estimated spare time of 1307.000;
restart ...

<snip about 15 lines of "delay of...">

delay of 16535.000 usecs exceeds estimated spare time of 1307.000;
restart ...
jack main caught signal 12
received signal 15 during shutdown (ignored)
no message buffer overruns

Adour then pukes saying it was kicked out by jack.

Asking around on #lad and #ardour has led me to believe it's a kernel
issue rather than a jack/client issue. However I *think* my kernel is
setup correctly. I've verified that the interface works well on OS X.
I've tested the on-board ac97 chip, there are less "delay" errors and
ardour doesn't die, although some messages still occur. I've read that
the usx2y alsa module provides "rawusb" access to that particular
hardware. Is there something similar to be used with the ua-25?

Any explanation or advice is welcome.

Specifically:
-reports of success with this hardware and any kernel
-hints/tips on finding killing those delay of XXX.XXX usecs exceeds...
messages
-opinions on the current state of affairs with alsa & USB
-other lists/resources to investigate regarding these types of errors

thanks in advance,
-ry

-- 
Ryan Gallagher <ruinaudio@email-addr-hidden>