radeon mobility x1600 broken since 3.4.0-rc6 (bisected)

[Hausensteiner Keg]

Hi,

I updated the kernel on an Ubuntu 12.04 (32-bit) install, and graphics 
immediately broke. Bisection points to:

commit bb635567291482a87e4cc46e6683419c1f365ddf
Author: Jerome Glisse <jglisse at redhat.com>
Date:   Wed May 9 15:34:46 2012 +0200

     drm/radeon: convert fence to uint64_t v4


Radeon graphics are still broken for me in both 3.5.2 (from 
linux-stable) and 3.6.3-rc3 - though the symptoms appear to be slightly 
different.

I'm currently running a kernel built from the commit before the above, 
and everything seems sane and stable.

I'm happy to do any tests you might find helpful..

== Symptoms

When booting with above commit, grub works fine but immediately upon 
attempt to switch graphics mode a solid green bar appears across the 
screen. System does not respond to ctrl-alt-f2. Very repeatable.

When booting with later releases (eg 3.5.2), the greeter screen is 
displayed - sometimes correctly, sometimes with minor graphics 
corruption. Immediately switching to a virtual terminal works. However 
any attempt to move the mouse or log in via the greeter screen causes 
graphics corruption and system no longer responds. Also consistently 
repeatable.

== OS details:

Ubuntu 12.04 32-bit (default kernel 3.2.0-29).

== System details:

HP/Compaq nc8430 laptop

$glxinfo | grep renderer ==> OpenGL renderer string: Gallium 0.4 on ATI 
RV530

$ lsmod | grep radeon
radeon                815703  3
ttm                    71375  1 radeon
drm_kms_helper         32563  1 radeon
drm                   220833  5 radeon,ttm,drm_kms_helper
i2c_algo_bit           13197  1 radeon

$ lspci | grep VGA
01:00.0 VGA compatible controller: Advanced Micro Devices [AMD] nee ATI 
M56P [Radeon Mobility X1600]

$ xrandr
Screen 0: minimum 320 x 200, current 1680 x 1050, maximum 8192 x 8192
VGA-0 disconnected (normal left inverted right x axis y axis)
LVDS connected 1680x1050+0+0 (normal left inverted right x axis y axis) 
331mm x 207mm
    1680x1050      60.1*+
    1400x1050      60.0
    1280x1024      59.9
    ....

Regards,
Simon