xrandr weirdness: cannot find crtc

[Gilad Arnold]

On Thu, Jun 18, 2009 at 10:08:18AM +1000, Alex Deucher wrote:
> > Looks like at least the mode I tested with explicitly, 1680x1050,
> > has the same timing rates (60.0). I believe (not tested right now,
> > not in front of the external monitor) that I can actually activate
> > both VGA-0 and DVI-0 at any mode (on the same rate) if I turn one
> > off, set the other to the desired mode, then set the first one to
> > the same mode.  I can test if you like.
> 
> You'll have to look at the actual mode lines (xrandr --verbose) to see
> is they are really indentical.  If the modes are indentical you should
> be able to drive both heads using the same crtc.

See below, first is VGA-0 and second is DVI-0.

$ xrandr --verbose | grep -A 2 1680x1050
  1680x1050 (0x57)  147.1MHz -HSync +VSync
        h: width  1680 start 1784 end 1968 total 2256 skew    0 clock   65.2KHz
        v: height 1050 start 1051 end 1054 total 1087           clock   60.0Hz
--
  1680x1050 (0x57)  147.1MHz -HSync +VSync
        h: width  1680 start 1784 end 1968 total 2256 skew    0 clock   65.2KHz
        v: height 1050 start 1051 end 1054 total 1087           clock   60.0Hz

> You can use the --crtc option with xrandr to force which crtc you want to
> drive a particular output.

$ xrandr --output DVI-0 --crtc 1 --mode 1680x1050 --rate 60.0
xrandr: cannot find crtc for output DVI-0

Exact same error. I have to switch off one of the two in order to change mode
on the other.

> >> Alternatively, xrandr isn't being smart about how it sets the mode which
> >> results in the error.
> >
> > If this is the case, where should I report this?
> 
> https://bugs.freedesktop.org

In the case that you are certain that this isn't a driver issue, let me know
and I'll file a bug.

Thanks!

Gilad