Bug#281286: xserver-xfree86: Starting X with USB mouse unpluged hardlocks system when Option "AGPMode" "4" used.
Hi Branden,
Thanks for your reply. I reported this problem as a bug just to have it
documented somewhere. I spent long hours trying to figure out if something
was wrong with hotplug or USB kernel modules, only to find out that problem
came from changing an XFree86 configuration option. I hope that by posting it
on Debian mailing list I might save somebody some troubleshooting time.
Perhaps it would be a good idea to put in X documentation that options such as
AGPMode, AGPFastWrite and EnablePageFlip are experimental and may cause
unpredictable problems when nondefault values are used. Presently, X
documentation does not warn a curious user like me that these are "deep
magic" options and should be used with caution.
It may be very well that in my case my system simply does not support AGPx4
speed. In the actual Dell advertisement is says explicitly that it does, but
how much you can trust that? Is there a way to check what is the speed AGP
supports? The 'lspci' does not give me any information about that.
Also, is it possible that this may be a BIOS problem? I talked to people who
had exactly the same laptop, but they experienced quite different problems
than me. The only difference was in BIOS versions. It seems that whenever
Dell releases a new BIOS version, it introduces new problems, and sometimes
solves some of the old ones. So, my educated guess would be that this happens
due to faulty BIOS. Does that make any sense?
Anyhow, thanks for your time and the great work that you and the rest of the X
Strike Force do. Cheers,
Slaven
On December 10, 2004 13:08, Branden Robinson wrote:
> retitle 281286 xserver-xfree86: USB plug/unplug events lock the system when
> Option "AGPMode" "4" used tag 281286 + moreinfo
> thanks
>
> On Sun, Nov 14, 2004 at 05:27:23PM -0500, Slaven Peles wrote:
> > This is a bizzare problem and it took me a while to figure out how to
> > reproduce it. On my laptop I configured Synaptics touchpad and USB
> > mouse. If I set device option "AGPMode" "4" whenever I start X without
> > USB mouse plugged or if I unplug the mouse while X is running, the whole
> > system hardlocks. The keyboard does not respond, and the screen is not
> > updated, i.e. all open applications stay frozen. Mice surprisingly can
> > move the cursor, but mouse buttons don't respond. It seems that processor
> > is under heavy load during that time, since the fan goes on very soon.
> >
> > If I leave default AGPMode, everything works fine, and I can plug and
> > unplug USB mouse as many times as I want. I've been doing that while
> > writing this report ;-). By the way setting AGPMode to 4 does not
> > improve performance (glxgears give same results regardless whether it is
> > 1 or 4).
>
> I hate to say this, but this problem may be a case of "don't do that,
> then".
>
> It is my understanding that "AGPMode" is a deep-magic option that only
> experts should fiddle with. If using it doesn't improve performance, then
> it's possible your system doesn't actually support 4X AGP transfers, and
> that when you enable it, your system bus timing is pushed so close to
> the edge that the interrupts generated when a USB device appears or
> disappears just send your hardware into panic mode.
>
> What do you think?
Reply to: