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Initially, I was running into the problem of black screen on boot up after a fresh installation and after seeing a solution which told me to add nomodeset after quiet splash from the grub screen, it really helped. I guess it is used to disable graphic/video drivers while booting. For permanent effect I added that line in the /etc/default/grub file.

I have AMD Radeon RX 640 along with Intel UHD as my graphics drivers. For some reason, I cannot boot into Ubuntu 20.04 LTS normally. I have to add nomodeset to boot into it. And if I do so, I cannot find my Graphics listed in About > Graphics. It shows llvmpipe (LLVM 10.0.0, 256 bits) in that place.

The command inxi -G gives the following output:

Graphics:
  Device-1: Intel CometLake-U GT2 [UHD Graphics] driver: N/A 
  Device-2: AMD Lexa [Radeon 540X/550X/630 / RX 640 / E9171 MCM] driver: N/A 
  Display: x11 server: X.Org 1.20.9 driver: fbdev unloaded: modesetting,vesa 
  resolution: 1920x1080~77Hz 
  OpenGL: renderer: llvmpipe (LLVM 11.0.0 256 bits) v: 4.5 Mesa 20.2.6

I have tried removing the nomodeset but if I do so, I cannot boot again.

Any information regarding this would be extremely helpful.

Ragu Raman
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2 Answers2

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Kernel Mode Setting (KMS) is a method for setting display resolution and depth in the kernel space rather than user space. The Linux kernel's implementation of KMS enables native resolution in the framebuffer and allows for instant console (tty) switching. KMS also enables newer technologies (such as DRI2) which will help reduce artifacts and increase 3D performance, even kernel space power-saving. With Kernel Mode Setting (KMS), the kernel is now able to set the mode of the video card. This makes fancy graphics during bootup, virtual console and X fast switching possible, among other things (see also this).

I am posting actions that may get you going.

Selective modeset

Selectively disable Kernel Mode Setting for one or the other graphics card by adding to the grub boot line (either temporary or permanent, you already know how to do both)

amdgpu.modeset=0
radeon.modeset=0
i915.modeset=0

for Radeon, Radeon (legacy driver), or Intel, respectively. The link also provides other alternatives to try.

Combine this with inxi -G as you did, and with lspci -k | grep -EA4 'VGA|3D'.

Reinstall

You may need to access recovery mode and reinstall drivers as shown here. Perhaps you can access a terminal (e.g. as in here) and do the same.

Related

  1. https://www.notebookcheck.net/Radeon-RX-640-vs-Radeon-620-vs-Radeon-610_9935_9927_9933.247598.0.html
  2. https://forums.linuxmint.com/viewtopic.php?t=122257
  3. https://www.udoo.org/docs-bolt/Operating_Systems/Linux/Known_issues.html
  4. https://itsfoss.com/fix-ubuntu-freezing/
sancho.s ReinstateMonicaCellio
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I had exact same problem with rx640 and ubuntu 20.04. this solution worked just right

be sure you are connected to the internet remove nomodeset from grub and update grub.black screen returns open terminal :

sudo apt-get purge lightdm
sudo apt-get update
sudo apt-get install lightdm
dpkg-reconfigure lightdm
sudo reboot
Reza Sam
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