Today I made my beagleboard Xm successfully play audio using the
2.6.37-rc8 Linux-omap kernel.
The problem you will face is "interface hw_params not set" when you
play any audio file using aplay or mplayer.
The fix is really simple. The condition "cpu_is_omap34xx" fails in
the function hw_params in file "sound/soc/omap/snd-omapmcbsp.c".
Just make the condition true and you are all set to play