https://bugzilla.kernel.org/show_bug.cgi?id=54381
--- Comment #14 from Andrew Stubbs ams@codesourcery.com --- More observations:
About 1 time in 3 boots the driver will fail to allocate PPLLs at all, and Ubuntu 13.10 will not start lightdm login screen.
Having failed, I tend to get a run of failures, but two or three reboots is usually sufficient to get a working setup once more. There just seems to be a random factor in there somewhere.
Please note: in these instances I have one monitor configured to run in a reduced resolution, so clock matching should not be a problem. I suppose it might be less problematic were I running all three screens at their preferred, default resolution.