Comment # 14 on bug 69694 from Marco

I found a workaround!

Disabling second GPU in xorg.conf let me enter in X with acceleration enabled:

marco@albireo:~$ glxinfo | grep -i opengl
OpenGL vendor string: X.Org
OpenGL renderer string: Gallium 0.4 on AMD KABINI
OpenGL version string: 2.1 Mesa 9.3.0-devel
OpenGL shading language version string: 1.30

Finally!!! And all is working fine.

Then the bug is related to having 2 GPU.
At least now I can play games (with only one GPU).