"radeon: ring 0 test failed" on boot ubuntu 14.04

I had the same issue with my laptop, a HP Probook 4530s with a ATI graphic cards. I'm also on Ubuntu 14.04.

I could solve my problem by doing this :

Add this line to your /etc/rc.local file, before "exit 0":

   echo OFF > /sys/kernel/debug/vgaswitcheroo/switch

And add this to /etc/modprobe.d/blacklist.conf

blacklist fglrx
blacklist radeon
alias radeon off
alias lbm-radeon off

It will disable your ATI discrete graphics card, this way you won't have any problem with Radeon when booting your laptop. Personally, my laptop works perfectly without the discrete card, I can use blender without problem for example.

I have exactly the same laptop, and bumped into that problem in Ubuntu 14.04. It seems that it's the fault of the open source driver for ATI graphic cards in Ubuntu 14.04.

I did these things and got rid of it:

• In BIOS settings I unchecked "Enable GPU switching" (something like it, don't remember exactly the label).
• Restarted and this time got past that problem, but Unity only showed the desktop and icon and no Launcher and decorations. This problem is solved by following this post.

NOTE: These are the steps that I think they solved my problem; because I was struggling for 3 hours and doing many things. I tried to use ATI's proprietary drivers (using Additional Drivers in Ubuntu). They didn't work and I removed them. I even installed the driver I downloaded from ATI website (which was working fine in my previous Ubuntu 12.04), but it didn't work either. I reinstalled ubuntu-desktop and Unity and many other things that I don't remember exactly.