SOLVED: Display problem after finishing dual-display

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Oldfiddler
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SOLVED: Display problem after finishing dual-display

Post by Oldfiddler »

Yesterday I was using dual display so that I could watch a live feed concert on a TV screen with hi-fi sound attached. I used mirrored screens and everything went fine. The TV is connected to the desktop by HDMI cable.

My problems started when I tried to get back to a single display. The Display application from the menu seems to have a mind of its own and wanted to make the TV the primary screen. Now my main monitor shows a partial desktop, with icons apparently off to one side and no menu bar at the bottom - I suspect the scaling is all wrong. The TV monitor shows nothing when the computer is in normal mode. Both monitors are active when I start up in Recovery mode. Then the menu bar also shows and I can get into the Display application - but that tells me that it is a laptop default display and fails to mention either of the actual monitors.

Please help me with some advice on getting back to a proper display on my computer monitor!

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~/Desktop$ inxi -Fxz
System:
Kernel: 5.4.0-126-generic x86_64 bits: 64 compiler: gcc v: 9.4.0
Desktop: Cinnamon 5.2.7 Distro: Linux Mint 20.3 Una
base: Ubuntu 20.04 focal
Machine:
Type: Desktop Mobo: ASUSTeK model: PRIME Z370-A II v: Rev X.0x
serial: <filter> UEFI: American Megatrends v: 0411 date: 09/21/2018
CPU:
Topology: Quad Core model: Intel Core i3-8100 bits: 64 type: MCP
arch: Kaby Lake rev: B L2 cache: 6144 KiB
flags: avx avx2 lm nx pae sse sse2 sse3 sse4_1 sse4_2 ssse3 vmx
bogomips: 28800
Speed: 800 MHz min/max: 800/3600 MHz Core speeds (MHz): 1: 801 2: 800
3: 800 4: 800
Graphics:
Device-1: Intel 8th Gen Core Processor Gaussian Mixture Model
vendor: ASUSTeK driver: i915 v: kernel bus ID: 00:02.0
Display: x11 server: X.Org 1.20.13 driver: modesetting
unloaded: fbdev,vesa resolution: 1920x1080~60Hz, 1680x1050~60Hz
OpenGL: renderer: Mesa Intel UHD Graphics 630 (CFL GT2) v: 4.6 Mesa 21.2.6
direct render: Yes
Audio:
Device-1: Intel 200 Series PCH HD Audio vendor: ASUSTeK
driver: snd_hda_intel v: kernel bus ID: 00:1f.3
Device-2: Logitech Webcam C270 type: USB driver: snd-usb-audio,uvcvideo
bus ID: 1-4:2
Sound Server: ALSA v: k5.4.0-126-generic
Network:
Device-1: Intel Ethernet I219-V vendor: ASUSTeK driver: e1000e v: 3.2.6-k
port: f040 bus ID: 00:1f.6
IF: eno1 state: up speed: 1000 Mbps duplex: full mac: <filter>
Drives:
Local Storage: total: 465.76 GiB used: 85.47 GiB (18.4%)
ID-1: /dev/nvme0n1 vendor: Samsung model: SSD 970 EVO 500GB
size: 465.76 GiB
Partition:
ID-1: / size: 456.89 GiB used: 85.47 GiB (18.7%) fs: ext4
dev: /dev/nvme0n1p2
Sensors:
System Temperatures: cpu: 29.8 C mobo: 27.8 C
Fan Speeds (RPM): N/A
Info:
Processes: 190 Uptime: 5m Memory: 15.50 GiB used: 719.6 MiB (4.5%)
Init: systemd runlevel: 5 Compilers: gcc: 9.4.0 Shell: bash v: 5.0.17
inxi: 3.0.38
Last edited by Oldfiddler on Fri Oct 07, 2022 2:38 pm, edited 1 time in total.
Oldfiddler
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Re: Display problem after finishing dual-display

Post by Oldfiddler »

I have been racking my brains to think of anything which might help someone to advise me. One thing you could find useful is this output:

Code: Select all

Desktop$ xrandr
Screen 0: minimum 320 x 200, current 3600 x 1080, maximum 16384 x 16384
DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)
HDMI-2 connected primary 1920x1080+1680+0 (normal left inverted right x
axis y axis) 1600mm x 900mm
    1920x1080     60.00*+  50.00    59.94    24.00    23.98
    1920x1080i    60.00    50.00    59.94
    1280x1024     60.02
    1280x720      60.00    50.00    59.94
    1024x768      60.00
    800x600       60.32
    720x576       50.00
    720x576i      50.00
    720x480       60.00    59.94
    720x480i      60.00    59.94
    640x480       60.00    59.94
HDMI-3 connected 1680x1050+0+0 (normal left inverted right x axis y
axis) 433mm x 271mm
    1680x1050     59.95*+
    1280x1024     75.02    60.02
    1280x960      60.00
    1152x864      75.00
    1024x768      75.03    70.07    60.00
    832x624       74.55
    800x600       72.19    75.00    60.32    56.25
    640x480       75.00    72.81    66.67    59.94
    720x400       70.08
I am struggling to make sense of this. When I right click on the desktop, the window says that I'm looking at a monitor on HDMI-3, with 1680 x 1050 resolution. It's connected but not primary. This main monitor for my computer is connected by DVI, not HDMI, because there seems to be only one HDMI connector on the computer. The other monitor (TV) which I use occasionally is on HDMI, but that's not showing anything, at least in normal mode.

I'd love to be able to get into the Display applet from the Menu, but I can't see the Menu and I don't know how to do it.

Any Ideas, please?
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SMG
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Re: Display problem after finishing dual-display

Post by SMG »

Oldfiddler wrote:
Thu Oct 06, 2022 6:09 am
My problems started when I tried to get back to a single display.
What steps did you take to get back to a single display?
Oldfiddler wrote:
Thu Oct 06, 2022 6:09 am
The TV monitor shows nothing when the computer is in normal mode. Both monitors are active when I start up in Recovery mode.
When you boot in recovery mode, the system automatically adds the nomodeset kernel parameter which prevents the graphics drivers from loading at boot time. You will not be able to get the system working properly in recovery mode.

Have you checked to make sure all the cable connections are secure at both ends for both monitors?

Have you tried a different cable? Sometimes they can go bad pretty quickly.

I suggest booting the computer with only one monitor attached. Do process of elimination to see what happens when you attach each one individually. If you can get both working properly when they are the only monitor, then try attaching both.
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A woman typing on a laptop with LM20.3 Cinnamon.
Oldfiddler
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Re: Display problem after finishing dual-display

Post by Oldfiddler »

Many thanks, SMG.

This is how I was trying to return to one display after using two. I went into the Display app, switched off mirrored displays, made the TV screen inactive, made sure the computer screen was active, with the appropriate resolution. Obviously some of that didn't work or was overridden by the app.

I tried your suggestion of booting up with only one screen connected. With the DVI connection (normal computer monitor), the boot was normal and the display was what I would expect, with the usual scaling and all the correct icons showing. I was able to enter the Display app and see that the screen was correctly identified and had the correct resolution, but the button to set the screen as primary did not operate.

With the HDMI connection only (TV screen), all the preliminary stuff showed correctly, ASUS, boot options etc. It got as far as the Mint log-in screen, just enough to see clearly what it was, and then the screen went blank, without any chance to log in.

I then booted with just the DVI connection - correct start, as before. I connected the HDMI cable and the DVI display immediately changed to the overblown size, with no toolbar at the bottom. Removing the HDMI put the DVI display back to normal. Nothing showed on the TV screen during these changes.

Finally, I went into the Display app and left it on screen when I reconnected the HDMI cable. The TV was recognised and I was able to control things, up to a point. I noticed that the button was active to make the HDMI option as the Primary, but it was inactive for the DVI display. I am now able to reboot and the DVI screen comes up with correct content a|nd scaling. Still nothing at all showing on the HDMI screen however, even when I set Mirrored displays. Clearly something is still wrong there. Perhaps I should try your idea of changing the HDMI cable - but it is verrrrrryyyyy long (and expensive!).

As the main problem has now been solved, thanks to your suggestions and my fumblings, I am inclined to mark this accordingly. Do you agree or are there other things you can suggest which might solve the dual display problem which has now emerged?

John
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SMG
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Re: Display problem after finishing dual-display

Post by SMG »

Oldfiddler wrote:
Fri Oct 07, 2022 9:06 am
This is how I was trying to return to one display after using two. I went into the Display app, switched off mirrored displays, made the TV screen inactive, made sure the computer screen was active, with the appropriate resolution. Obviously some of that didn't work or was overridden by the app.
I presume you clicked Apply for the changes. It sounds like it may be an issue of the information the graphics driver received (or did not when it should have) may have caused the change.
Oldfiddler wrote:
Fri Oct 07, 2022 9:06 am
I was able to enter the Display app and see that the screen was correctly identified and had the correct resolution, but the button to set the screen as primary did not operate.
Was there only one screen showing as active in the Display app at that time? That may be why the option to set it as primary was not available. (I do not have a multi-screen set-up and can not check that option.)
Oldfiddler wrote:
Fri Oct 07, 2022 9:06 am
With the HDMI connection only (TV screen), all the preliminary stuff showed correctly, ASUS, boot options etc. It got as far as the Mint log-in screen, just enough to see clearly what it was, and then the screen went blank, without any chance to log in.
We have had cases where people have not been able to get a display from an HDMI connection. In those cases, we can often enable the HDMI port and, if needed, supply EDID information. However, those are usually cases where it never worked at all rather than a change like what happened in your case. We can give that a try if you want.
Oldfiddler wrote:
Fri Oct 07, 2022 9:06 am
I am now able to reboot and the DVI screen comes up with correct content a|nd scaling. Still nothing at all showing on the HDMI screen however, even when I set Mirrored displays. Clearly something is still wrong there. Perhaps I should try your idea of changing the HDMI cable - but it is verrrrrryyyyy long (and expensive!).
What is the make and model of the TV and its preferred resolution?

What is the output of

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ls /sys/class/drm/
and the current output of (if it is different than what you posted earlier)

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xrandr
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Oldfiddler
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Re: Display problem after finishing dual-display

Post by Oldfiddler »

Hi again, SMG,

I just turned the TV on again, after it had a good lie-down this afternoon. And lo and behold, it worked fine as a second display!

When I came out again from dual screens, it was a bit temperamental, trying to reset mirror displays when I'd switched them off, and setting odd resolutions when I'd reset to the DVI screen resolution. Also, the Display app was a bit unstable, seeming to want to migrate to the TV screen, rather than stay on the DVI screen.

I think I'm going to mark this one as solved, and will bear in mind these problems next time I'm trying to set dual displays (and unset them!)

Thanks again for all your help.

John
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SMG
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Re: SOLVED: Display problem after finishing dual-display

Post by SMG »

Glad to hear it is working. Sometimes the Universe sends us mysteries we never understand what happened, but I never argue with working electronics. :)
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