some details reg. Sound DMA (output) timeout

Ulf Jaenicke-Roessler (ujr@physik.phy.tu-dresden.de)
Thu, 30 Apr 1998 14:06:02 +0200 (MDT)


Hi,

from several reports on this list I know that the

Sound DMA (output) timeout

message is a more or less common problem with the latest
kernels.

First of all, the problem doesn't depend on the sound driver
compiled into the kernel or as module. The error shows up
in both cases.
However, using sound as module may cause real trouble: when
I loaded (or let kerneld/kmod load) the modules and used it
once, it was ok. The second time the DMA problem occurred.
Then I removed the sound modules (rmmod) and tried to reload
them (insmod). Bang! The kernel freezes. No message, no log,
no SysRQ, nothing.
It seems that certain resources aren't freed and can't be
initialized again.

I tried several of the latest development kernels and
realised that the problem started (at least for me) with
2.1.90. This means, 2.1.89 was ok with respect to this problem
and the (fairly large) 2.1.90 patch introduced the bug.
So I tried the sound driver of 2.1.89 with 2.1.90 (ie, I
copied the hole linux/drivers/sound directory). And voila, it
worked!
Later I will try that with 2.1.98 too.

Unfortunately, I wasn't able to find the real cause from the
patch, but it looks like a lot of DMA closing/freeing has been
removed (though it may be replaced, and I didn't notice that)

Maybe this helps to fix the problem.

Regards,

Ulf

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