I'm running Raspbian Jessie Lite using a HifiBerry AMP+. Everything works perfectly using the dtoverlay=hifiberry-amp device tree overlay for kernel >=3.18.
When I enable experimental support for WebGL (I use the same Pi to drive a web-based dashboard), then the hifiberry is no longer detected (dmesg shows 'snd_soc_register_card() failed: -517'). Since enabling experimental WebGL support adds an additional device tree overlay (dtoverlay=vc4-kms-v3d) I'm wondering if this is some sort of conflict. When I comment out the vc4-kms-v3d overlay then the hifiberry-amp works perfectly again.