Radeon *error* uvd not responding trying to reset the vcpu

[Master]

Option-1: If Ubuntu is able to boot:

1. sudo nano /etc/default/grub
2. Change the line GRUB_CMDLINE_LINUX="" to GRUB_CMDLINE_LINUX="radeon.modeset=0" or, GRUB_CMDLINE_LINUX="nomodeset" and Save the file
3. sudo update-grub && sudo systemctl reboot

Option-2: If Ubuntu is not able to boot:

1. To edit Grub during the boot, do the following:
2. Immediately after the BIOS splash screen during boot, press and hold the SHIFT button. This will display you grub containing a list of kernels and recovery options
3. Press e to edit the kernel
4. Find the line ending with quiet splash. Add your boot option before these key words – i.e. so the line looks like nomodeset quiet splash
5. ctrl+x to boot

It should work now. Also remember, if you want to permanently use nomodeset, then, after boot, follow my Option-1.

[DaMysterious]

I had a very similar problem and fixed it by editing the default grub file with

   sudo nano /etc/default/grub

and changing the line

   GRUB_CMDLINE_LINUX=""

to

   GRUB_CMDLINE_LINUX="radeon.modeset=0"

then saving the file and updating the grub with

   sudo update-grub

and rebooting. If the above does not work then perhaps try out changing the

   GRUB_CMDLINE_LINUX="radeon.modeset=0"

to

   GRUB_CMDLINE_LINUX="nomodeset"

. And check the dmesg log for errors with

  dmesg | grep radeon