I'm experiencing this bug as well. Can anyone spot a problem with this configuration?

Linux 14.04LTS clean install

$ uname -srm
Linux 3.13.0-46-generic x86_64

$ grep -Rn radeon.audio /etc/default/grub
11:GRUB_CMDLINE_LINUX_DEFAULT="quiet splash radeon.audio=1"

$ xrandr -q
Screen 0: minimum 320 x 200, current 5200 x 2130, maximum 16384 x 16384
DisplayPort-0 connected primary 1600x900+80+1050 (normal left inverted right x axis y axis) 443mm x 249mm
   1600x900       60.0*+
   1280x1024      75.0     60.0  
   1280x960       60.0  
   1280x800       59.8  
   1152x864       75.0  
   1280x720       60.0  
   1024x768       75.1     70.1     60.0  
   832x624        74.6  
   800x600        72.2     75.0     60.3     56.2  
   640x480        75.0     72.8     66.7     60.0  
   720x400        70.1  
DisplayPort-1 connected 1600x900+1680+1050 (normal left inverted right x axis y axis) 443mm x 249mm
   1600x900       60.0*+
   1280x1024      75.0     60.0  
   1280x960       60.0  
   1280x800       59.8  
   1152x864       75.0  
   1280x720       60.0  
   1024x768       75.1     70.1     60.0  
   832x624        74.6  
   800x600        72.2     75.0     60.3     56.2  
   640x480        75.0     72.8     66.7     60.0  
   720x400        70.1  
DisplayPort-2 connected 1680x1050+0+0 (normal left inverted right x axis y axis) 473mm x 296mm
   1680x1050      59.9*+
   1400x1050      74.9  
   1280x1024      75.0  
   1440x900       75.0     59.9  
   1152x864       75.0  
   1024x768       75.1     70.1     60.0  
   832x624        74.6  
   800x600        72.2     75.0     60.3     56.2  
   640x480        75.0     72.8     66.7     60.0  
   720x400        70.1  
DisplayPort-3 connected 1680x1050+1680+0 (normal left inverted right x axis y axis) 473mm x 296mm
   1680x1050      59.9*+
   1400x1050      74.9  
   1280x1024      75.0  
   1440x900       75.0     59.9  
   1152x864       75.0  
   1024x768       75.1     70.1     60.0  
   832x624        74.6  
   800x600        72.2     75.0     60.3     56.2  
   640x480        75.0     72.8     66.7     60.0  
   720x400        70.1  
DisplayPort-4 connected 1920x1080+3280+1050 (normal left inverted right x axis y axis) 1600mm x 900mm
   1920x1080      60.0*+   50.0     59.9     24.0     24.0  
   1920x1080i     60.1     50.0     60.0  
   1280x720       60.0     50.0     59.9  
   1440x576       50.0  
   1440x576i      50.1  
   1440x480       60.0     59.9  
   1440x480i      60.1     60.1  
   720x576        50.0  
   720x480        60.0     59.9  
   640x480        60.0     59.9  
DisplayPort-5 disconnected (normal left inverted right x axis y axis)

$ sudo lspci -vk | grep -A15 VGA
03:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Cape Verde PRO [FirePro W600] (prog-if 00 [VGA controller])
        Subsystem: Advanced Micro Devices, Inc. [AMD/ATI] Device 2b1e
        Flags: bus master, fast devsel, latency 0, IRQ 67
        Memory at c0000000 (64-bit, prefetchable) [size=256M]
        Memory at d4000000 (64-bit, non-prefetchable) [size=256K]
        I/O ports at 2000 [size=256]
        [virtual] Expansion ROM at d4060000 [disabled] [size=128K]
        Capabilities: [48] Vendor Specific Information: Len=08 <?>
        Capabilities: [50] Power Management version 3
        Capabilities: [58] Express Legacy Endpoint, MSI 00
        Capabilities: [a0] MSI: Enable+ Count=1/1 Maskable- 64bit+
        Capabilities: [100] Vendor Specific Information: ID=0001 Rev=1 Len=010 <?>
        Capabilities: [150] Advanced Error Reporting
        Capabilities: [270] #19
        Kernel driver in use: radeon

$ lspci -v | grep Audio
03:00.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] Cape Verde/Pitcairn HDMI Audio [Radeon HD 7700/7800 Series]
        Subsystem: Advanced Micro Devices, Inc. [AMD/ATI] Cape Verde/Pitcairn HDMI Audio [Radeon HD 7700/7800 Series]
11:01.0 Multimedia audio controller: C-Media Electronics Inc CMI8738/CMI8768 PCI Audio (rev 10)
        Subsystem: C-Media Electronics Inc CMI8738/C3DX PCI Audio Device

$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: HDMI [HDA ATI HDMI], device 3: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: HDMI [HDA ATI HDMI], device 7: HDMI 1 [HDMI 1]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: HDMI [HDA ATI HDMI], device 8: HDMI 2 [HDMI 2]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: HDMI [HDA ATI HDMI], device 9: HDMI 3 [HDMI 3]
  Subdevices: 0/1
  Subdevice #0: subdevice #0
card 0: HDMI [HDA ATI HDMI], device 10: HDMI 4 [HDMI 4]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: HDMI [HDA ATI HDMI], device 11: HDMI 5 [HDMI 5]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: CMI8768 [C-Media CMI8768], device 0: CMI8738-MC8 [C-Media PCI DAC/ADC]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: CMI8768 [C-Media CMI8768], device 1: CMI8738-MC8 [C-Media PCI 2nd DAC]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: CMI8768 [C-Media CMI8768], device 2: CMI8738-MC8 [C-Media PCI IEC958]
  Subdevices: 0/1
  Subdevice #0: subdevice #0