Figuring out where in the display stack an eGPU + external 4k display is breaking
by jdally987 from LinuxQuestions.org on (#5HA2A)
Hey all, I've been dealing with this issue for a long time and never really knew where to start diagnosing the issue, so would just appreciate any advice on where to hone in on the problem.
I have an eGPU and trying to connect my laptop through it to an external display over Thunderbolt.
Here's what I'm working with:
Problem is it doesn't seem to detect the external display at all. No other displays show up in KDE display settings or in the /var/log/messages output. Other problems: if I originally booted up the laptop without the eGPU connected, when I connect the cable, the X session freezes up for some reason. Everything is still visible on-screen and I can move the cursor, but nothing is clickable and whatever was on the display at the time of connecting the egpu freezes completely (i.e. the clock in the screen corner doesn't change, UI elements such as the X to close windows don't light up when moused over etc..) until I either hard reboot/sysrq+b reset; ctrl+alt+backspace to kill the X session; or sometimes I think I can ctrl+alt+1 to switch to another virtual terminal.
Log up to this point (start = plugging in egpu; stop = when I reboot):
https://pastebin.com/bYUh2Fgd
If I connect the eGPU first and THEN boot up, the system is at least fully usable, although still no external display detected. But if I disconnect the eGPU and switch to using the laptop on battery while still booted, it either freezes immediately or sometimes keeps running fine until it sleeps or the display turns off, at which point waking it back up only shows a black screen with an unmoveable cursor. Then I have to reset again.
Log for that scenario (fresh boot while plugged in):
https://pastebin.com/5DGxSJzW
I know it's not exactly my hardware itself but probably something in the way it's configured with NixOS, because booting a regular Ubuntu live ISO works just great - hotplugging the egpu makes the display come up immediately and everything works smoothly. Although sometimes I have noticed the X server freezing thing even on Ubuntu too. Another small problem is I've never gotten either GNOME or KDE to run this 4k TV at 60hz - something that works fine on windows through the same egpu. But not as much of a priority as getting it working *at all* on nixos, and not forcing me to shut down & restart every time I unplug it.
I have an eGPU and trying to connect my laptop through it to an external display over Thunderbolt.
Here's what I'm working with:
- Laptop: LG Gram 17 (i7-8565u, Intel UHD 620 integrated graphics)
- eGPU: Razer Core X
- Video card in eGPU: AMD RX 470
- external display: Sceptre 4k 60hz TV (connected via HDMI to GPU)
- OS: NixOS 21.05
- DE: KDE Plasma 5.21.3
- Graphics stack: X11
- Kernel: 5.11.14
Problem is it doesn't seem to detect the external display at all. No other displays show up in KDE display settings or in the /var/log/messages output. Other problems: if I originally booted up the laptop without the eGPU connected, when I connect the cable, the X session freezes up for some reason. Everything is still visible on-screen and I can move the cursor, but nothing is clickable and whatever was on the display at the time of connecting the egpu freezes completely (i.e. the clock in the screen corner doesn't change, UI elements such as the X to close windows don't light up when moused over etc..) until I either hard reboot/sysrq+b reset; ctrl+alt+backspace to kill the X session; or sometimes I think I can ctrl+alt+1 to switch to another virtual terminal.
Log up to this point (start = plugging in egpu; stop = when I reboot):
https://pastebin.com/bYUh2Fgd
If I connect the eGPU first and THEN boot up, the system is at least fully usable, although still no external display detected. But if I disconnect the eGPU and switch to using the laptop on battery while still booted, it either freezes immediately or sometimes keeps running fine until it sleeps or the display turns off, at which point waking it back up only shows a black screen with an unmoveable cursor. Then I have to reset again.
Log for that scenario (fresh boot while plugged in):
https://pastebin.com/5DGxSJzW
I know it's not exactly my hardware itself but probably something in the way it's configured with NixOS, because booting a regular Ubuntu live ISO works just great - hotplugging the egpu makes the display come up immediately and everything works smoothly. Although sometimes I have noticed the X server freezing thing even on Ubuntu too. Another small problem is I've never gotten either GNOME or KDE to run this 4k TV at 60hz - something that works fine on windows through the same egpu. But not as much of a priority as getting it working *at all* on nixos, and not forcing me to shut down & restart every time I unplug it.