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Okay, i wanted to ask this on amd support directly but i cant create an account there because there suppoort forum does not work (omfg, sometimes i really ask myself if EVERYTHING is fu**** BROKEN these days)

Okay, lets explain my problem: At work i assembled a new pc featuring a amd graphics card (RX 550) and 2 Iiyama WQHD Screens (2560x1440). Everything worked fine using the default configuration. One Screen is attached via DisplayPort and the other via DVI.

Now i wanted to dig a little into WebGL and 3D and figured it might be good to install the latest gpu drivers directly from the vendor. So i installed the amdgpu-pro driver like explained on the amd website.

After rebooting the DVI attached screen is configured to 1920x1200 and i dont have an option to set it back to 2560x1440.

Whats so extraordinary in my setup?

I dont get it, whats so exotic in connecting 2 Screens to a new graphics card? Using the current Long-Term-Support Release of one of the biggest linux distributions in the world? Why cant this sh** just work?

I had similar problems with a notebook i used some months ago. That notebook had a Nvidia Gforce GTX1030 or something like that built in.

How could i solve this without wasting massive time in learning about Xorg (what i really dont want to, i dont care so much about lowlevel stuff, just want this machine to do like its supposed to)

lshw -C display output

  Beschreibung: VGA compatible controller
  Produkt: Advanced Micro Devices, Inc. [AMD/ATI]
  Hersteller: Advanced Micro Devices, Inc. [AMD/ATI]
  Physische ID: 0
  Bus-Informationen: pci@0000:23:00.0
  Version: c7
  Breite: 64 bits
  Takt: 33MHz
  Fähigkeiten: pm pciexpress msi vga_controller bus_master cap_list rom
  Konfiguration: driver=amdgpu latency=0
  Ressourcen: irq:305 memory:e0000000-efffffff memory:f0000000-f01fffff ioport:e000(Größe=256) memory:fe800000-fe83ffff memory:c0000-dffff

What confuses me here is the "VGA Compatible Controller", I installed the correct driver like explained, my video card is listed here

When running grep -i chipset /var/log/Xorg.0.log

i get

  [   157.137] (II) RADEON: Driver for ATI/AMD Radeon chipsets:
  [   157.139] (II) VESA: driver for VESA chipsets: vesa
  [   157.141] (--) AMDGPU(0): Chipset: "Radeon RX 550 Series" (ChipID = 0x699f)

Why does linux have to be so much pain all the time :-(

When i executed the following script i got it working the notebook featuring the nvidia graphics.

  #!/usr/bin/env bash
  sudo xrandr --newmode "2560x1440_56" 225.000 2560 2608 2640 2720 1440 1443 1448 1481 +hsync -vsync
  sudo xrandr --addmode HDMI-1-2 "2560x1440_56"
  sudo xrandr --output HDMI-1-2 --mode "2560x1440_56"
  exit

But hey - i dont really know what i am doing there so i would prefer a real fix for my problem.

And one final Off-topic Question: Is there ONE Distribution/GPU Combination that works - that you could recommend? I learned, that AMD is absolutely horrible I learned, that Nvidia is even worse!!

Is there only intel IGPU left?

Philipp Wrann
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2 Answers2

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I am using amdgpu-pro on Arch and amdgpu open source on Solus and the latest update I did caused the same issue with my 1440p ASUS PB278Q connected to a Radeon r9 390.

I can no longer find the 2560x1440 mode in either distro, and if I add it manually via xrandr on Arch it fails to apply with a generic "failed to change mode" error.

I can't say exactly why this is happening, but from the evidence here it's probably not the linux kernel or the hardware, so it's likely the graphics driver. Given that amdgpu-pro and open source are both causing this, it's most likely the amdgpu stack. Not a certain answer, but the most likely place to find a solution for now. If it is amdgpu then this is an AMD issue and not a problem with the Linux environment itself.

SOLVED for me! Just now, only minutes after writing this, my own investigation found my solution. So here it is:

Add amdgpu.dc=0 to the kernel parameters.

Easy, right? I hope it works for you!

Nathan Bozeman
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When using HDMI instead of DVI i am able to set up my monitors correctly. But it cant be a hardware-limitation as it worked perfectly with the built-in driver, it has to be related to amdgpu-pro.

My initial problem is solved by switching the video output, but the issue remains in the amdgpu-driver. If you have problems using 3 outputs with WQHD you might want to contact AMD directly.

Philipp Wrann
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