When I set the fragmentation to 64x256 or 8x2048 or some other similar
value, I get the sound. Otherwise, the driver reports "channel dead"
and there is silence. My suspicion is that the DMA buffer has to be
allocated at a 16kB segment boundary, which does not always happen when
its size is <16kB. Unfortunately, I do not know FreeBSD kernel well enough
to verify and fix this problem.
Could somebody with enough expertise please look at it and try fixing
the problem? Because of this, I can't test several programs planned for