[arch-general] Display issues with Linux 3.1

[Taylor Hedberg]

Since updating to Linux 3.1 yesterday, I've been having strange problems
with the display on my laptop. The first reboot after updating the
kernel went normally, but every subsequent boot since then has had
problems.

This is a Dell Latitude D620 laptop with the following graphics-related
lines in the lspci output:

00:02.0 VGA compatible controller: Intel Corporation Mobile 945GM/GMS, 943/940GML Express Integrated Graphics Controller (rev 03)
00:02.1 Display controller: Intel Corporation Mobile 945GM/GMS/GME, 943/940GML Express Integrated Graphics Controller (rev 03)

During boot, at the stage where it says "Waiting for UDev uevents to be
processed", the backlight normally blinks and the display mode changes,
presumably due to udev detecting my graphics hardware. 

Since the kernel update, the backlight still blinks off momentarily, but
when it comes back on, the screen remains blank. Rather than seeing the
rest of the boot messages, the display is just black (but backlit). The
system still seems to boot like normal; I boot to the virtual console
rather than starting X automatically, and once the hard disk activity
stops after booting, I can blindly type my login credentials and issue
shell commands, though I still can't see any output.

Additionally, after the first reboot following the update (which did not
have the aforementioned display problems), I had issues with the display
backlight after starting X. If I shut the laptop lid, the backlight
usually shuts off, and comes back on when I reopen it. However, after
the kernel update, around 80% of the time, the backlight seemed to come
back on at about a third of its usual brightness. I had to close and
reopen it several times, and eventually it would come on at full power
like normal.

I managed to boot the system in single-user mode using the fallback
initcpio image (any other combination of boot options seemed to result
in the blank screen), and then downgraded the kernel back to 3.0.7.
After downgrading, all of these problems seem to have disappeared.

I've scanned through dmesg output and I don't really see anything out of
the ordinary. But I admit that I don't really know what I'm looking for.
Any thoughts or suggestions?