Second Monitor Not Working on 5.x Kernels

TheVE

So I've been stuck on the 4.x LTS kernels this whole time because when I try a 5.x kernel, my second monitor stops working. It's time to figure this out because my writing tablet needs a 5.x kernel and last week reading SDXC cards stopped working on 4.x for some reason but works fine on 5.x.

Symptoms:
When second monitor is enabled I see a screen that stays black 99% of the time with brief flashes of the desktop that last a fraction of a second before going back to black. My primary monitor works fine.

The monitor works perfectly in 4.x kernels.

In 5.x kernels it is detected and setup in the display settings in my desktop but when enabled, it glitches as described.

The problem exists on any DE.

I have no idea where to start to figure this out so any help is much appreciated. 😀

System:
1700x
RX480
Solus Plasma
Fully updated and verified.

Dean

TheVE I don't think it's a issue with the 5.x Kernel, maybe it's something with that kernel on the plasma version. I have a laptop connected with monitor and has been working perfectly after I updated to kernel 5.
Maybe the issue is with the AMD GPU drivers not working properly on the kernel 5, have you dried uninstalling and reinstalling them?

System:
i5-6300HQ
GTX 950M
Solus Budgie

TheVE

Dean
I've tried reinstalling mesalib but nothing changes.

Dean

TheVE I don't know much about AMD GPU on linux as I have Nvidia, but maybe you can try reintall xorg-driver-video-amdgpu.

TheVE

Dean

Tried reinstalling xorg-driver-video-amdgpu. No change. Thanks for the suggestion.

In case it helps, I downloaded the latest Linux Mint ISO and booted it from a thumb drive. Same problem. So I'm at a total loss here.

🙁

Dean

TheVE Do you know if the OS is detecting it? Have you tried different resolution and refresh rate?
Check the different resolution option with xrandr command on the terminal.

TheVE

Dean

I just spent the last little bit looking into how xrandr works after reading about someone with a similar problem needing to change their refresh from 60hz to 59hz. So that's what I tried but manually adding a 59hz mode since the only refresh rate listed was 60hz. It worked!

Process:
cvt 1680 1050 59 xrandr --newmode 1680x1050_59.00 143.75 1680 1784 1960 2240 1050 1053 1059 1089 -hsync +vsync xrandr --addmode HDMI-A-1 1680x1050_59.00 xrandr --output HDMI-A-1 --mode 1680x1050_59.00

And bam, on came my monitor. I have no idea why it was detected wrong. If anyone can explain to me why and how to keep it from happening in the future, I'd appreciate it. 🙂

And not sure if this makes it permanent?

But I'll mark this down as a linux noob win.

Cheers

pomon

It only works for one session. Create a file:

#!/bin/bash

xrandr --newmode 1680x1050_59.00 143.75 1680 1784 1960 2240 1050 1053 1059 1089 -hsync +vsync
xrandr --addmode HDMI-A-1 1680x1050_59.00
xrandr --output HDMI-A-1 --mode 1680x1050_59.00

chmod +x /created/file
A double click will turn on the monitor. You can add this file to the autostart.