radeon kms, LCD timing info

[Howard Chu]

I have an HP dv5z laptop with HD3450 GPU. It came with a 1680x1050 LCD panel
and I'm currently trying to use a 1920x1200 panel instead. The panel that I
have seems to work fine as far as booting and text mode goes, but when I start
up X I get a black screen. By the way, this is currently running Ubuntu Jaunty
but with a self-compiled 2.6.32-rc4 kernel and X stuff from the xorg-edgers
ppa, so fairly bleeding edge driver and mesa.

Another interesting bit is that with the fbcon driver, the VTs also work fine,
and I have 75 rows x 240 columns of text. So it appears that the radeon driver
is using acceptable timing parameters at startup, but when the X server starts
it switches to a set of timing parameters that don't work.

First question: how do I find out what timing parameters are in use at boot,
and what's in use by radeon+fbcon?

Second question: how do I set the correct timing parameters while X is
running? Just playing with modelines doesn't seem to be sufficient. X boots up
with several modelines but most of them are defective. E.g., 1920x1080
actually displays the desktop instead of just a black screen, but it is
shifted right by about an inch, and has a cyclic fade-to-white going on. Many
of the other modes do the same thing, and a few (like 640x480) just display black.

Any help would be much appreciated, thanks.
-- 
  -- Howard Chu
  CTO, Symas Corp.           http://www.symas.com
  Director, Highland Sun     http://highlandsun.com/hyc/
  Chief Architect, OpenLDAP  http://www.openldap.org/project/