Bug 16846

please attach your xorg log and config.

Created attachment 17916 [details]
xorg.conf

Created attachment 17917 [details]
Xorg.0.log

Does changing the mode on the VGA port help? E.g.,
xrandr --output VGA-0 --mode 800x600

Also, does the VGA port work if you start X without the monitor attached, and then enable the monitor via xrandr after x is started?
xrandr --output VGA-0 --auto

Right, here's lots of information. I've tried to be as verbose as possible to properly explain what I'm doing. I'm sorry it's a long read!

If I boot the laptop with the monitor connected it shows all the "ThinkPad screen" plus grub et al. on both monitors. When X starts, the same thing continues, with VGA-0 being a nice mirror image of LVDS. In xrandr, VGA-0 gives many possible modes. The possible modes are: 1280x960, 1280x800, 1152x864, 1280x768, 1024x768, 832x624, 800x600, 640x480, 720x400 and 640x350. The possible modes of LVDS stay constant at 1024x768, 800x600 and 640x480. "xrandr --output VGA-0 --off" does work, and switching it back on is also successful. If on the default mode of 1024x768, I use "xrandr --output VGA-0 --mode 800x600", VGA-0 continues to show at 1024x768 (the same as LVDS) and xrandr shows the selected mode as being 800x600. If I try to use "xrandr --output VGA-0 --left-of LVDS --auto" then I get the "screen cannot be larger than AxB" message. If I add the "Virtual" entry in my xorg.conf under "Section Screen" and "SubSection "Display"", the "cannot be larger than AxB" message disappears, and there is clearly two displays, but both monitors are cloned on the same display. I can easily tell there are two displays, or the screen has been extended because I can lose my mouse off the edge of the screen.

If I boot the laptop *without* the monitor connected, it obviously boots up all on LVDS. When X is started, xrandr successfully tells me that VGA-0 is disconnected. If I plug in the monitor cable, another call to xrandr shows me that VGA-0 is online, and shows the same modes as listed before for both VGA-0 and LVDS. Calling "xrandr --output VGA-0 --auto" powers up the external monitor, and clones LVDS successfully, EXCEPT that the picture on VGA-0 horribly vibrates from side-to-side. If I use "--mode 800x600", the same behaviour as above happens. Calling "--left-of LVDS" also shows exactly the same behaviour as above: it outputs the "cannot be larger than" message normally, and with "Virtual 2048 2048" it creates two displays, but only shows one on both monitors. The picture vibration still occurs through all of these steps if the monitor is not plugged in at bootup.

Pressing Fn+F7 (the key for changing monitor behaviour) doesn't do anything when the machine is booted, but for some seconds on bootup it does allow to switch between: showing picture on LVDS only, showing picture on VGA-0 only, and showing picture on both. I conducted the above tests with the latter option as the bootup was shown on both monitors. If I select the option of only showing the bootup on LVDS, the VGA-0 is powered off for bootup but is powered up when X starts. It mirrors LVDS as usual when X is started (and stops doing so when X is stopped). Exactly the same thing happens if I boot up *without* the external monitor plugged in. The picture vibration also continues to occur.

So, to sum up:
 * Pressing Fn+F7 makes no difference to X behaviour.
 * The picture is cloned whatever is asked for.
 * The resolution of the external monitor does not change if requested, but reports a different resolution in xrandr.
 * The "Virtual" line in xorg.conf is required to even attempt --left-of.
 * When the machine is not booted up with the cable attached, the picture vibrates from side-to-side horribly.

Thank you. I hope this is of some help.

You are probably getting clone mode and the xrandr utility is not smart enough to request different crtcs for each head when dualhead is requested.  Try the following:
xrandr --output VGA-0 --off
xrandr --output VGA-0 --crtc 1 --mode 1024x768
xrandr --output VGA-0 --left-of LVDS

There is no change in the behaviour at if I do as you suggest. --output VGA-0 --off switches the monitor off, --crtc 1 --mode 1024x768 switches on the monitor in clone mode, --left-of LVDS blanks the two monitors for a second or so, but then the two come back on cloned. They both show the right of the two displays (this is obvious because the mouse can be "lost" on the left hand side).

Is this still an issue with xf86-video-ati from git master?

closing due to lack of feedback.