video problem after upgrade to 20.04
 

Hi All,

This problem should be an easy fix, but I have no idea how to start to research this question.

I had, for some time, been running my dell laptop (Xubuntu 19) with an external lenovo monitor (using mode 1366 x 768) on the HDMI port, and the laptop monitor disabled.

I decided, perhaps foolishly, to accept an upgrade to Ubuntu 20.04, without disconnecting that external monitor or enabling the laptop screen. The whole upgrade went fine, until the time came to restart....

Upon restarting the computer, it comes to the login screen as normal. The display is fine at the login screeen.

However, after putting in my password, when it logs in the screen goes crazy. Everything that should be vertical goes diagonal.

So, I played around a bit and found out that if I unplug the Lenovo and reinsert the cable, the problem is "fixed", both external and laptop monitors do work fine, but only with the Lenovo set to the 1920 x 1080 mode and the laptop on 1366 x 768.

If I try to change those settings, the diagonal chaos ensues. (I think I can turn the laptop screen on and off, but I don't want to test that now, as I may not be able to get back to this post if I do.)

Any ideas?

Thanks in advance,

Andrew.

Hi All,

Update. It turns out that I can use essentially any mode on both the laptop and the external monitor except the 1366 x 768 mode. As long as I don't use that mode, I can run the laptop by itself, without the external monitor, shutdown restart etc no problems.

Interestingly, on restart, the laptop screen scrambles for a moment on laptop and then comes good in whatever mode it was set to before shutdown,as long as it was not the 1366 x 768 mode. This is with the external monitor unplugged.

Is it possible the 1366 x768 mode on both the laptop and the external got scrambled in the upgrade. Could this perhaps be fixed with xrandr --addmode?

Cheers....

Andrew.

1-Why are you finding it necessary to do this mode switching?

2-Try creating a new user. If the problem is not reproduced logging in using the new user, then user settings would be at fault. Otherwise, system settings would be at fault.

3-Try using a fallback session selected from your login greeter if another type is provided, such as IceWM, to isolate whether or not your DE session type is involved.

4-Try using a different method of selecting a mode. What method are you using?

5-Provide us information about the Lenovo. Paste here using code tags ( # icon above input area; to preserve the formatting) combined graphical terminal input & output from:6-Provide us logs from X running OK, and from not running OK. Current X session log is normally Xorg.0.log. Previous X session log is normally Xorg.0.log.old. These are found in either ~/.local/share/xorg/ or /var/log/. If found in both locations, choose which to upload based upon newest timestamps. Do not attempt to paste these large log files here directly. These large files can be uploaded using pastebinit, or by going to http://pastebin.com/ or http://paste.ubuntu.com/ or equivalent text file temporary sharing site.

7-Try switching DDX. Check out this driver primer that explains the choices.

Hi mrmazda,

let me try to answer your qns.

1. I am only doing the mode switching to investigate the problem. I want to use 1366 x 768 on both machines, which is about the only thing I can't do. It cannot be a coincidence that this is the mode I was using during the upgrade, and the only one totally broken now is the 1366 x 768 on the Lenovo.

2. I setup a new user. Same for both, so I agree likely system settings.

3. The greeter is setup to offer only xfce4 and xubuntu sessions. And it makes no difference.

4. Please advise what methods of mode selection are available. I am using the GUI, " settings" "Display". I am also aware of xrandr. But there is probably another text command for this?

5. This is what I got from inxi -SGXX. Device 1 is Dell, so that one is the laptop, but I don't see device 2. On the back of the monitor, the model number is lt2423wc, and manuf. year 2014. I may not have done the code tags right, but it looks all readable anyway.
#
System:
Host: andrew-Inspiron-3180 Kernel: 5.4.0-42-generic x86_64 bits: 64
compiler: gcc v: 9.3.0 Desktop: Xfce 4.14.2 tk: Gtk 3.24.13 wm: xfwm4
dm: LightDM Distro: Ubuntu 20.04.1 LTS (Focal Fossa)
Graphics:
Device-1: AMD Stoney [Radeon R2/R3/R4/R5 Graphics] vendor: Dell
driver: amdgpu v: kernel bus ID: 00:01.0 chip ID: 1002:98e4
Display: x11 server: X.Org 1.20.8 driver: amdgpu,ati
unloaded: fbdev,modesetting,vesa resolution: 1440x900~60Hz
OpenGL: renderer: AMD STONEY (DRM 3.35.0 5.4.0-42-generic LLVM 10.0.0)
v: 4.5 Mesa 20.0.8 direct render: Yes
#

6. log files. I found two sets of log files at /var/log and none at the other location.

One set is a few files named like xorg.0.log etc, and seems to relate to the laptop screen. The other is xorg.1.log, relating to the HDMI screen, with vendor "LEN", and some references to the other screen too. These files are quite long. Before I paste the whole thing in here, can you explain what you mean by "X running ok" and "X not running ok"? I mean, don't these logfiles cover a whole session, which would include times when the display is working and also times when it is not.

7. I think it's a bit early to change the driver already (although it might work). The coincidence is just too great that the only mode that is screwing up is the one I was using during the upgrade. This is the only time I ever upgraded with an external monitor connected and I was a bit concerned that doing so might cause issues.



What did you think of using xrandr to resetup the modes on the Lenovo?



Thanks for your help.

Cheers....

Andrew.

Hi Mrmazda,

I'm a fool. I cut the power to the goddamned monitor, then turned it back on again, and all is now well. Previously I had only switched it off with the on off switch.

Sorry about wasting your time!

Cheers.....

Andrew.