Intel GM45: Loop of continuously triggered output detections

[Peter Clifton]

This didn't send first time....


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.

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-- 
Peter Clifton

Electrical Engineering Division,
Engineering Department,
University of Cambridge,
9, JJ Thomson Avenue,
Cambridge
CB3 0FA

Tel: +44 (0)7729 980173 - (No signal in the lab!)