Description of problem:
Ironlake driver in 5.5 has several bugs that prevent full functionality, including PLL setup parameters and search algorithm being wrong, pipe depth being misconfigured, clocks not being fully enabled, etc.
The most notable side effect of this is that dualhead does not work.
Patch more or less in hand, just working out a final bug where repeated DPMS cycles deadlock the machine.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
http://rhn.redhat.com/errata/RHBA-2012-0289.html