Debian Hardware :: Jessie - Radeon HDMI Audio Not Working On Kernels 3.12 And Up

I am running a small Debian Jessie installation on my Zotac Nano AD10 (based on AMD's E-350, Radeon 6310). I use it as an MPD server, it outputs to my receiver over HDMI.

Up until kernel 3.11 that works fine. My GRUB command line looks like this (default grub.cfg file):

Code: Select all$ grep radeon /etc/default/grub
GRUB_CMDLINE_LINUX_DEFAULT="quiet elevator=noop radeon.audio=1 radeon.dpm=1"

Up till 3.11, this worked fine. The available outputs in alsamixer are unmuted [00]. Aplay reports this:

Code: Select all$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: Generic [HD-Audio Generic], device 3: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: SB [HDA ATI SB], device 0: ALC892 Analog [ALC892 Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

I also set the HDMI output as system-wide default:

Code: Select all$ cat /etc/asound.conf
pcm.!default {
      type plug
      slave {
      pcm "hw:0,3" # HDMI audio
      }
        }

Running speakertest on device 0,3 though, - no sound:

Code: Select all$ speaker-test --device plughw:0,3

speaker-test 1.0.27.2

Playback device is plughw:0,3
Stream parameters are 48000Hz, S16_LE, 1 channels
Using 16 octaves of pink noise
Rate set to 48000Hz (requested 48000Hz)
Buffer size range from 64 to 16384
Period size range from 32 to 8192
Using max buffer size 16384

[Code] ...

I've tried fixing this repeatedly (3.12, 3.13, 3.14) but everytime i find myself returning to 3.11 because that keeps working.... Some posts suggest running xrandr could get it working, but this is a headless installation, so I cannot use xrandr.

For reference, OpenELEC works on this same system (separate install), and they're up to 3.14 as well. Never had a problem with OpenELEC and the audio not working.