I'm trying to enable kernel debug logging like this:

# echo "file sound* +pflm" > /sys/kernel/debug/dynamic_debug/control

But it has no effect until after I load the Device Tree Overlay that creates my codec and sound card nodes. Unfortunately at this point, it's too late for the debugging to do any good.

This is with kernel 4.1.9 on a Beaglebone Black Debian Jessie distro.

I don't really know how the kernel dyndebug system works; I am able to enable other debugging locations, but none in sound/*

Appreciate any guidance. Thank you.