Xorg AMDGPU

I own a AMD Vega64 and an using it with i3 on Manjaro. The misaligned monitors on the greeter and the manual resolution and refresh rate switching were super annoying.

Setup

• Updated Manjaro with kernel >5.0 including amdgpu kernel driver
• AMD Vega64
• Monitor capable of 144Hz and Freesync
• Second Monitor not capable of those things

144Hz modline

This was relative simple, amdgpu is pretty verbose on startup and prints all available modlines for the connected outputs on the card into /var/log/Xorg.0.log. With a simple less /var/log/Xorg.0.log I quickly found it somehwere along with

[     6.454] (II) AMDGPU(0): Printing probed modes for output DisplayPort-2
[     6.454] (II) AMDGPU(0): Modeline "2560x1440"x60.0  241.50  2560 2608 2640 2720  1440 1443 1448 1481 +hsync -vsync (88.8 kHz eP)
[     6.454] (II) AMDGPU(0): Modeline "2560x1440"x143.9  586.00  2560 2568 2600 2640  1440 1465 1473 1543 +hsync -vsync (222.0 kHz e)
[     6.454] (II) AMDGPU(0): Modeline "2560x1440"x119.9  482.64  2560 2568 2600 2640  1440 1447 1455 1525 +hsync -vsync (182.8 kHz e)
[     6.454] (II) AMDGPU(0): Modeline "2560x1440"x99.9  398.23  2560 2568 2600 2640  1440 1496 1504 1510 +hsync -vsync (150.8 kHz e)

and used the one with my desired configuration.

xorg config

To get my setup working as expecting without manual configuration on every startup, I needed to place a persistent config in the xorg config folder so e.g. /etc/X11/xorg.conf.d/10-monitors.conf. There, I configured both my GPU driver and the monitors like following.

The Monitor sections are straightforward. DisplayPort-2 is my 144Hz display, so I added the modline as a new preset 2560x1440_full and used it in the PreferredMode option. Further I enabled DPMS, the Display Power Management Signaling so the system could turn of the Montiors just in case.

The Device section contains the preferred options for the given GPU drive, in my case amdgpu. I enabled TearFree as well as VariableRefresh, the first one should reduce tearing on both displays while the latter one enables FreeSync on my 144Hz monitor. After a reboot, my monitor indeed reported it was using FreeSync!

Section "Monitor"
  Identifier "DisplayPort-2"
  Modeline "2560x1440_full"  586.00  2560 2568 2600 2640  1440 1465 1473 1543 +hsync -vsync
  Option "Primary" "true"
  Option "PreferredMode" "2560x1440_full"
  Option "DPMS" "true"
EndSection

Section "Monitor"
  Identifier "DisplayPort-1"
  Option "PreferredMode" "2560x1440_59.95"
  Option "LeftOf" "DisplayPort-2"
  Option "DPMS" "true"
EndSection

Section "Device"
  Identifier "AMD-VEGA"
  Driver "amdgpu"
  Option "VariableRefresh" "true"
  Option "TearFree" "true"
EndSection