[arch-general] Display issues with Linux 3.1

Sebastian Schwarz seschwar at googlemail.com
Thu Nov 10 10:36:54 EST 2011


On 2011-11-09 at 19:55 -0500, Taylor Hedberg wrote:
> 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)

I have a Dell Latitude D420 with the same card.

> 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.

I do not have this problem, however this sounds familiar:

> 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.

My display comes back with the minimal brightness setting.
Also the XF86MonBrightnessUp (Fn+Up) and XF86MonBrightnessDown
(Fn+Down) buttons stopped working.  I can restore the previous
brightness level and the buttons by running:

    cat /sys/class/backlight/intel_backlight/max_brightness \
            > /sys/class/backlight/intel_backlight/brightness

The bug can easily triggered in X by running:

    xset dpms force off

> After downgrading, all of these problems seem to have
> disappeared.

I haven't bothered to downgrade the kernel yet.

> 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 found this I my dmesg output:

    [Firmware Bug]: Duplicate ACPI video bus devices for
    the same VGA controller, please try module parameter
    "video.allow_duplicates=1"if the current driver doesn't

But I also haven't tried this, as the incorrect brightness has
not annoyed me enough, yet.


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