[arch-general] 2x 1440p displays not working on thunderbold dock anymore

[Tasnad Kernetzky]

On 14.09.19 16:13, Ricardo Band wrote:
> Ahoi,
>
> I use Arch on a Thinkpad T480 with the Lenovo Thunderbold 3 dock. I've
> attached 2 1440p monitors to it and I was using them for a while now.
> For a few days or so I can't get them to work anymore. Usually I
> disable my Notebooks internal screen and enable the 2 1440p displays
> like this:
>
> ```
> xrandr --output DP1-1 --mode 2560x1440 --refresh 144
> xrandr --output eDP --off
> xrandr --output DP1-2 --mode 2560x1440 --refresh 144 --right-of DP1-1
> ```
>
> This used to work quite nicely. No idea if the refresh rate actually
> worked. I have no way to test that but the resolution sure did.
>
> Now when I do this I get this error:
>
> ```
> xrandr: Configure crtc 0 failed
> ```
>
> I can only drive both displays at 1920x1080. When I increase the
> resolution to 2560x1440 I get this error and the higher resolution
> can't be set.
>
> I don't know why this doesn't work anymore. Could it be a driver issue?
> I've got a nvidia GPU with the proprietary driver and the integrated
> intel with the open source driver and it wouldn't be the first time
> intel or nvidia fucked their drivers up.
>
Hi Ricardo,

I know this error message very well. For me, giving "--crtc" values to
xrandr works perfectly for 3 years now:

xrandr --output eDP1 --crtc 0 --mode 1920x1080 --output DP1 --crtc 1
--primary --mode 2560x1440 --pos 1920x0 --output DP2 --crtc 2 --mode
2560x1440 --pos 4480x0

You can check which virtual crtcs your GPU has with xrandr --verbose,
but usually it's 0, 1 and 2 like above.

I only have an integrated Intel GPU, but the error message sounds very
familiar.


Best,

Tasnad


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