16.04: R9 380X, third monitor blank -- but recognized by system settings.

[QIII]

Hello!

I'm running an R9 380X (Volcanic Islands) with the AMDGPU driver. All three monitors are recognized in system settings, they are not mirrored but extended, the third monitor is there and I can drag windows to it, but the output is black.

Is anyone running 16.04 with an AMD Volcanic Islands GPU with three monitors?

OS, hardware disclosure:

OS: Kubuntu 16.04, installed on SSD
Mobo: Gigabyte 990FXA UD3
CPU: AMD FX-8350
MEM: 16GB
GPU: R9 380X

It's definitely running amdgpu:

xenial@ZACK:~$ lsmod | grep amd
kvm_amd                65536  0
kvm                   536576  1 kvm_amd
edac_mce_amd           24576  0
amdkfd                122880  1
amd_iommu_v2           20480  1 amdkfd
amdgpu                983040  6
i2c_algo_bit           16384  1 amdgpu
ttm                    98304  1 amdgpu
drm_kms_helper        139264  1 amdgpu
drm                   360448  9 ttm,drm_kms_helper,amdgpu

and not radeon:

xenial@ZACK:~$ lsmod | grep radeon
xenial@ZACK:~$

All three monitors are accounted for:

xenial@ZACK:~$ xrandr 
Screen 0: minimum 320 x 200, current 5760 x 1080, maximum 16384 x 16384
DisplayPort-0 connected primary 1920x1080+1920+0 (normal left inverted right x axis y axis) 509mm x 286mm
   1920x1080     60.00*+  50.00    59.94  
   1920x1080i    60.00    50.00    59.94  
   1680x1050     59.88  
   1280x1024     75.02    60.02  
   1440x900      74.98    59.90  
   1280x960      60.00  
   1152x864      75.00  
   1280x720      60.00    50.00    59.94  
   1440x576      50.00  
   1024x768      75.08    70.07    60.00  
   1440x480      60.00    59.94  
   832x624       74.55  
   800x600       72.19    75.00    60.32    56.25  
   720x576       50.00  
   720x480       60.00    59.94  
   640x480       75.00    72.81    66.67    60.00    59.94  
   720x400       70.08  
HDMI-A-0 disconnected (normal left inverted right x axis y axis)
DVI-D-0 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 510mm x 287mm
   1920x1080     60.00*+
   1680x1050     59.88  
   1280x1024     60.02  
   1440x900      59.90  
   1280x800      59.91  
   1152x864      75.00  
   1024x768      70.07    60.00  
   800x600       60.32    56.25  
   640x480       66.67    60.00  
   720x400       70.08  
DVI-I-1 connected 1920x1080+3840+0 (normal left inverted right x axis y axis) 509mm x 286mm
   1920x1080     60.00*+
   1600x1200     60.00  
   1680x1050     59.88  
   1400x1050     59.95  
   1280x1024     75.02    60.02  
   1440x900      59.90  
   1280x960      60.00  
   1152x864      75.00  
   1024x768      75.08    70.07    60.00  
   832x624       74.55  
   800x600       72.19    75.00    60.32    56.25  
   640x480       75.00    72.81    66.67    60.00  
   720x400       70.08

The GPU is properly recognized:

xenial@ZACK:~$ lspci | grep VGA
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Amethyst XT [Radeon R9 M295X Mac Edition / R9 380X] (rev f1)

[QIII]

OK, so, um ...

Next time, check to see that the DVI-D going out is attached to a monitor that will take a DVI-D signal ...

So embarrassed.