Enable onboard sound on mainline kernel

phkr

Hi all!
I am using Firefly RK3399 with mainline kernel (distro: ARMtix) but i can't make onboard sound work. By default it is not detected at all.
I've tried to tweak kernel a bit, namely i added kernel config option which added a module for rt5640 codec to kernel and set "okay" status for i2s1 node in board device tree. With this rebuilt kernel ALSA detects the existance of rt5640 codec, i can hear a snap when i plug in headphones but no sound is played/recorded even with aplay/arecord utilities. What else should i do to make sound work?
Before running mainline kernel i used Rockchip one from slarm64 image for this board. The result was same as with patched mainline kernel