Using HDMI output breaks displayport permanently

[Shevek]

If I have a thunderbolt monitor, it works fine-ish, most of the time, and I can connect, disconnect, etc.

If EVER I connect to an HDMI monitor, it connects and will disconnect, but then displayport NEVER WORKS AGAIN until I reboot the laptop.

After using and disconnecting HDMI:

shevek@starling:~$ xrandr -q
Screen 0: minimum 8 x 8, current 3840 x 2160, maximum 32767 x 32767
DP-0 connected (normal left inverted right x axis y axis)
   2560x2880 60.00 +
DP-1 connected (normal left inverted right x axis y axis)
   4096x2304 60.00 +
   3840x2160 60.00
   3200x1800 60.00
   2560x2880 60.00
   2560x1440 60.00
   640x480 59.94
HDMI-0 disconnected (normal left inverted right x axis y axis)
eDP-1-1 connected 3840x2160+0+0 (normal left inverted right x axis y axis) 344mm x 193mm
   3840x2160 60.00*+ 59.98 59.97
   3200x1800 59.96 59.94
   2880x1620 59.96 59.97
   2560x1600 59.99 59.97
   2560x1440 59.99 59.99 59.96 59.95
(etc)

BUT:
+ xrandr --output DP-1 --mode 3840x2160 --above eDP-1-1
xrandr: Configure crtc 0 failed
X Error of failed request: BadValue (integer parameter out of range for operation)
  Major opcode of failed request: 140 (RANDR)
  Minor opcode of failed request: 21 (RRSetCrtcConfig)
  Value in failed request: 0x0
  Serial number of failed request: 55
  Current serial number in output stream: 55

and then the screen goes blank. And now I have to reboot again, which is kind of meh because of #1852797 the laptop crashes every day or two anyway on 19.10 where it didn't crash on 19.04 but ... still a pain.

This bug existed on 19.04 with nvidia-driver-418 and exists in nvidia-driver-430.

ProblemType: Bug
DistroRelease: Ubuntu 19.10
Package: xserver-xorg-video-nvidia-430 430.50-0ubuntu2
ProcVersionSignature: Ubuntu 5.3.0-23.25-generic 5.3.7
Uname: Linux 5.3.0-23-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.11-0ubuntu8.2
Architecture: amd64
CurrentDesktop: XFCE
Date: Wed Nov 20 15:16:06 2019
InstallationDate: Installed on 2019-01-21 (303 days ago)
InstallationMedia: Xubuntu 18.10 "Cosmic Cuttlefish" - Release amd64 (20181017.2)
SourcePackage: nvidia-graphics-drivers-430
UpgradeStatus: Upgraded to eoan on 2019-11-10 (10 days ago)

[Shevek (r-launchpad-anarres-org)]

Additional notes:
* When I enable the HDMI port, I used --mode 1920x1080 --scale-from 2840x2160
* I have just discovered that I _can_ reenable the DP using nvidia-settings, but ONLY as a mirror-of or BELOW my existing laptop screen. What I cannot do is make the DP screen be ABOVE my laptop screen. It's as if using the HDMI port (with scale-from?) has locked the laptop screen to X coordinates (0,0).

[Shevek (r-launchpad-anarres-org)]

And for the full LOL, `xrandr --output eDP-1-1 --mode 3840x2160 --below DP-1` works, but `xrandr --output DP-1 --mode 3840x2160 --above eDP-1-1` did not.