xrandr weirdness: cannot find crtc

[Alex Deucher]

On Mon, Jun 29, 2009 at 3:01 PM, Gilad Arnold<arnold at cs.berkeley.edu> wrote:
> 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.

Seems like an xrandr bug to me.

Alex