* Taylor Hedberg <tmhedberg@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.