Intel GM45: Loop of continuously triggered output detections

[Jin, Gordon]

Peter Clifton wrote on Tuesday, January 13, 2009 11:45 AM:
> On Tue, 2009-01-13 at 01:55 +0000, Peter Clifton wrote:
>> Testing git HEAD intel drivers, also recent Xorg:
>> 
>> 
>> After the problem with miss-detected TV-out, I killed Xorg with a
>> Ctrl +Alt+Backspace (I've got zapping re-enabled in my xorg.conf),
>> and the outputs detected properly, with no TV output detected as
>> being connected. 
>> 
>> The performance was very slow, however, and with the characteristic
>> "jiggle" / jittering of the mouse cursor position which I've noticed
>> on both my Intel based machines during output detection.
>> 
>> Trying xrandr, adjusting brightness, had no effect. A couple of VT
>> switches to VT1 and back to Xorg finally stopped the detection loop,
>> although during that process, one of the the switches to VT1 left me
>> with a corrupted console. (Possibly scanning out from the wrong part
>> of the frame-buffer, perhaps with the wrong sync settings?).
>> 
>> I've attached the log. It does show a page-table problem with the
>> last VT switch.
> 
> I managed to re-trigger this bug by pulling the laptop's AC power
> adaptor out, and plugging it back in again. I suspect either an ACPI
> event, or something inside HP's SMM BIOS code triggered it. My old HP
> nc 6320 didn't properly respect _DOS bit 4, so would always fiddle
> with the graphics hardware when you plugged / unplugged the AC
> adaptor. 
> 
> I've not dug deeply into this one, so I'm not quite blaming the BIOS
> yet, however it is looking somewhat guilty.

This looks similar to http://bugs.freedesktop.org/show_bug.cgi?id=19431, interesting bug.

Gordon