Comment 8 for bug 1274115

you can use

 # Enable basic debugging and dump stack, check hardware pointer on all updates
 # Usefull to just see, if PCM stream is stopped for a reason (usually wrong audio process timing from scheduler)
 # And to do the exact check the values from driver
 echo 27 > /proc/asound/card0/pcm0p/xrun_debug

or

# Enable basic debugging, do jiffies check and dump position on each period and hardware pointer update calls
 # Usefull when the lowlevel (specific) hardware driver is somehow broken
 echo 29 > /proc/asound/card0/pcm0p/xrun_debug