I recently installed 18.04 and seemed well. The system detected both monitors I have and all was fine. 2 days ago my screens went blank suddenly, not waking up from a few key presses or a wiggle of the mouse, I rebooted the machine. Now Ubuntu is only on one of these monitors. I performed a fresh install but the issue still persists. I have also downloaded and installed the latest AMD GPU driver from https://support.amd.com/en-us/kb-articles/Pages/Radeon-Software-for-Linux-Release-Notes.aspx and no change. (slight change in that now I get a very slight flicker now and again)

This particular machine is dual boot with Windows 10 and that performs fine - detecting both monitors. Even the BIOS displays over two screens so am pretty sure this isn't hardware related.

I'm not looking for 3D acceleration or anything on my Ubuntu partition - just two monitors for working.

This kind of thing really is beyond me but some output from some various commands:

lspci -nnk | grep -i vga -A3 | grep 'in use'
     Kernel driver in use: amdgpu

sudo lshw -c video
       description: VGA compatible controller
       product: Ellesmere [Radeon RX 470/480/570/570X/580/580X]
       vendor: Advanced Micro Devices, Inc. [AMD/ATI]
       physical id: 0
       bus info: pci@0000:25:00.0
       version: e7
       width: 64 bits
       clock: 33MHz
       capabilities: pm pciexpress msi vga_controller bus_master cap_list rom
       configuration: driver=amdgpu latency=0
       resources: irq:47 memory:e0000000-efffffff memory:f0000000-f01fffff ioport:f000(size=256) memory:fe900000-fe93ffff memory:c0000-dffff

Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 16384 x 16384
DisplayPort-0 disconnected (normal left inverted right x axis y axis)
DisplayPort-1 disconnected (normal left inverted right x axis y axis)
HDMI-A-0 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 531mm x 299mm
   1920x1080     60.00*+  50.00    59.94  
   1600x1200     60.00  
   1680x1050     59.88  
   1280x1024     60.02  
   1440x900      59.90  
   1280x960      60.00  
   1280x800      60.00  
   1280x720      60.00    50.00    59.94  
   1152x720      59.97  
   1024x768      60.00  
   800x600       60.32    56.25  
   720x576       50.00  
   720x480       60.00    59.94  
   640x480       66.67    60.00    59.94  
HDMI-A-1 disconnected (normal left inverted right x axis y axis)
   1920x1080     60.00  
DVI-D-0 disconnected (normal left inverted right x axis y axis)

Any help or guidance would be massively appreciated!

  • 2
    Try adding amdgpu.dc=0 to the kernel command line at boot, to see if it helps.
    – dobey
    Jun 16 '18 at 19:03
  • You, sir. are legendary! Thank you! Please add an answer and I will accept it. Would you be able to elaborate as to why this works? Just so I can at least try and understand what's happening - always found configuring displays a nightmare sometimes with Ubuntu.
    – Zakalwe
    Jun 16 '18 at 21:27
  • @dobey Thanks very much, this successfully enabled dual monitors for an RX 580 with Debian Buster. Sep 25 '20 at 4:16
  • I had an issue about dual monitors but very different from the one here.. but il also solved it! My problem was: when inactive, both screens went dark but re-uped after few seconds instead of having a "no signal" displayed.. hmmmm
    – purerstamp
    Mar 21 at 17:56

Based on the @dobey ansewer:

  1. Run sudo nano /etc/default/grub
  2. Change GRUB_CMDLINE_LINUX_DEFAULT and save:
GRUB_CMDLINE_LINUX_DEFAULT="splash amdgpu.dc=0"
  1. Run sudo update-grub
  2. Reboot your system

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