[arch-general] Display issues with Linux 3.1

[Uli Armbruster]

* Taylor Hedberg <tmhedberg at gmail.com> [10.11.2011 01:55]:
> 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?

I can confirm this behavior, however I'm not sure if it's software related. I have the impression that this happens here only if the laptop is cold (e.g. because I carried it around outside in the cold german autumn). But Taylor's describtion fits perfectly to the behavior I have, so maybe it really is caused by the kernel.

I have a
01:00.0 VGA compatible controller: ATI Technologies Inc RV350 [Mobility Radeon 9600 M10]
and use the radeon driver.