Reported by: Jean-Philippe Guérard (Bugzilla Bug 1782)

"I've tried with video=atyfb:debug and video=atyfb:debug,mode:1280x600, \
nomtrr.

In both case, the screen stays black, but seems divided into 4 vertical bands.
 Some white lines pop up randomly on each vertical band."

The problem is a combination of an incorrect xclk plus lack of timing
information.  The adapter is attached to an LCD device that can do 1280x600
(which is not a standard resolution).  The global mode database does not have
an entry for it.  Fortunately, the Video BIOS contains the complete timing
info for this display, however, atyfb is not making use of it.

Add support to get the timing information from the BIOS, if available.
Signed-off-by: Antonino Daplas <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>