External monitor will not activate (cannot find crtc for output)

[Tim Holy]

This is a new problem with my upgrade to Kubuntu Karmic (this worked fine in previous releases).

xrandr recognizes my external monitor, but when I try to activate it with
$ xrandr --auto
or
$ xrandr --auto --output VGA-0 --mode 1280x1024
I get the following error:
 xrandr: cannot find crtc for output VGA-0

It clearly knows about the monitor:
$ xrandr
Screen 0: minimum 320 x 200, current 1400 x 1050, maximum 1600 x 1600
VGA-0 connected (normal left inverted right x axis y axis)
   1280x1024 60.0 + 75.0 60.0
   1280x960 60.0
   1152x864 75.0
   1024x768 75.0 70.1 60.0
   832x624 74.6
   800x600 72.2 75.0 60.3 56.2
   640x480 75.0 72.8 66.7 59.9
   720x400 70.1
LVDS connected 1400x1050+0+0 (normal left inverted right x axis y axis) 285mm x 214mm
   1400x1050 60.0*+ 50.0
   1280x1024 59.9 60.0
   1280x960 59.9
   1280x854 59.9
   1280x800 59.8
   1280x720 59.9
   1152x768 59.8
   1024x768 60.0 59.9
   800x600 60.3 59.9
   640x480 59.9 59.4
DVI-0 disconnected (normal left inverted right x axis y axis)

Note that I was formerly connected to my monitor at work (the DVI-0 entry). I have tried doing this:
$ xrandr --output DVI-0 --off

It may also be worth noting that my work monitor has "high" resolution (1600x1200), and I've noticed a number of flaky things about X in handling that resolution (for example, I have to restart X to get full resolution if I haven't started X with that monitor connected before). In other words, it's possible that this won't be easily replicable without the right combination of hardware.

My home monitor is a ViewSonic VP930b. I'm not at work right now, I don't remember the model # of the work monitor (but can provide it if needed).

ProblemType: Bug
Architecture: i386
Date: Fri Nov 6 04:40:45 2009
DistroRelease: Ubuntu 9.10
Package: libxrandr2 2:1.3.0-2
ProcEnviron:
 LANGUAGE=en
 PATH=(custom, user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.31-14.48-generic
SourcePackage: libxrandr
Uname: Linux 2.6.31-14-generic i686

[Tim Holy (holy-wustl)]

I can add that, in Lucid Alpha 3, X won't even start if this monitor is connected at boot time.

[Tim Holy (holy-wustl)]

This bug is still present in Maverick alpha (daily build 2010-08-26). The error now reads:
  cannot find crtc for output DVI-0
If you need the log files, would it be best to start a new bug with ubuntu-bug? Or if you list which files you want attached, I can do that also.

[Tim Holy (holy-wustl)]

In Maverick alpha (daily build 2010-08-27) this bug is still present.

I can't figure out how to add tags myself, can someone please explain or please add a "maverick" tag so this gets looked at during the evaluation process?

[Tim Holy (holy-wustl)]

I should have added that my hardware configuration is slightly different now:
Laptop: Thinkpad T60, with a 1400x1050 screen (4:3)
Home external monitor: Dell S2409W with 1920x1080 resolution (16:9)
Work external monitor: HP LP2065 with a 1600x1200 resolution (4:3)

However, the behavior is identical to what I initially reported.

[Tim Holy (holy-wustl)]

See these upstream bug reports:
https://bugs.freedesktop.org/show_bug.cgi?id=29929
https://bugs.kde.org/show_bug.cgi?id=249636

And this one explains the issues:
https://bugs.freedesktop.org/show_bug.cgi?id=29852

[Timo Aaltonen (tjaalton)]

So it's a limitation of userland mode setting, and since we default to KMS now it shouldn't be an issue anymore. UMS is largely unsupported by us on -ati, -intel and -nouveau only support KMS.