Linux: Forcing a specific resolution and refresh rate on a dummy display dongle

Operating Systems & Open Source Linux
1

Hey all,

Admittedly I’m a little stumped on this one. I’ve got a couple of Displayport dummy head dongles that fool a computer into thinking that there is a display attached so I can remote desktop into the computers with Sunshine. The problem with the dongles is that they do have the GPU run at 4K, but only at 17hz; I want it running at 60hz.

I’ve been using video= arguments as shown in this article to send a 4K signal, and while it worked on a Dell 1920x1080 DP display I had lying around (The monitor didn’t display the image, but that’s OK.), when I plugged in the dongle to replicate the setup for the dummy dongle, it shows up as an HDMI device; so I quickly fixed my kernel argument, but when it boots, dmesg is saying that the mode isn’t supported ([drm] User-defined mode not supported: "3840x2160":).

I’m not sure exactly what’s happening, but is anyone able to shed some light on this? Thanks in advance!

2

That article is good. It also shows you how to figure out reported and supported modes by a display. Did you try doing that for the dongle too? Just asking to make sure.

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@anon27729519 Yes, I did try that. It did report the resolutions the it claims to support. I’m still confused on why it worked on the Dell display and not the dongle. The only thing different was that it showed up as an HDMI device connected to the DP port instead of a native DP device.