[SOLVED] Flickering screen after I wake up the PC

[Qqmike]

I want to throw this out to see if any of you guys have some insights to a problem and maybe can offer 'best' or other fixes for it. Kubuntu 20.04.

Problem:

After leaving the PC for awhile, I return, I move the mouse to wake it up the PC, BUT the screen flickers with colorful, blinking patterns of horizontal and vertical colored bars and patterns.
This has happened 4 times since 12/1/21 (until today 12/26/21).
Btw, I CAN log in and continue that way, but with a flickering screen.

Comment:
The video RAM not being re-initialized when the machine emerges from the sleep state?
Caused by the video driver?

Hardware:

The graphics is integrated, Intel UHD Graphics 630. FYI, here's the specs:

– CPU Intel Core i5-10500 - 10th Gen Comet Lake 6-Core 3.1 GHz LGA 1200 65W Intel UHD Graphics 630
– Monitor Asus VA24EHE 23.8” Monitor, 1080P, Full HD, IPS, 75Hz, HDMI D-Sub DVI-D,
– Motherboard ASUS Prime Z590-P LGA 1200 (Intel 11th/10th Gen) ATX
– Memory Crucial 32GB Kit (2 x 16GB) DDR4-2666 UDIMM, CT2K16G4DFD8266

Proposed solutions and what happened:

(1) This failed:

Ctrl – Alt -F3, log in, exit, then go back to graphical: Ctrl – Alt – F1
This has failed – it takes me back to the flickering screen.

(2) This worked:

At the flickering screen, I logged in with U/N and PW. Then logged out. Then logged in again.
That worked to get rid of the flickering screen.

(3) This also worked, but please keep reading:

I get the flickering screen. I hit Ctrl – Alt - F3. I log in with U/N and PW.
Then I do:

sudo systemctl restart sddm.service

I enter my PW and it gives me a non-flickering screen, with a twist:

(a) Once, this worked perfectly, and I could continue on with the Kubuntu 20.04 desktop & proceed OK, no problems.

(b) Another time when I tried this, it gave me a non-flickering screen OK, but my Kubuntu desktop didn’t fully load: the mouse pointer wasn’t working right; the Firefox tabs wouldn’t reload; I had no panel at the bottom of the screen (showing the K- app launcher or system tray or open apps, etc.)
=> So, that time I did a hard re-boot of the PC and then everything came up OK -- I could continue with no problems.


Questions:
Advice? Thoughts? Other solutions? Diagnosis/analysis?

[DoYouKubuntu]

The only times I've seen that behavior was when the graphics card needed to be replaced. It's been a very long time since I experienced that, so my memory is not too good, but intermittent, random behavior rings a bell. IOW, when you're seeing it 'fixed' I don't think it really is--I just think it's dumb luck that it happens to be 'fixed' for a while after you've been mucking about. Let's see what others think...

[Qqmike]

But my graphics is integrated graphics; i.e., no discreet graphics card. Which suggests compatibility with the graphics driver? I really don't know much about graphics! Doesn't happen often: Let's say I wake the PC up maybe 15 times a day (maybe more than that), for 30 days = 450 times; and it's only happened 4 times (out of 450). Something to do, maybe, with the state of things in video Ram at the instant I am waking up the PC ... ?

[DoYouKubuntu]

I was going to say "or a driver issue" but chose not to. Oh well. *shrug*

Have you tried reinstalling the graphics driver(s)? Perhaps something became corrupted, or there's an update, or... ?

Graphics problems, per se, have [luckily] not been an issue for me for a long time, so let's see what others have to say.

[Snowhog]

Given how you are able to remedy the condition, I'd be inclined to say it's corrupted VRAM when the PC is awakened from sleep mode. I can't say how that would happen, but....

[Qqmike]

Your comments make sense, but raises more questions about things I don't know much about -- graphics!
I would think that I have a pretty standard system, not bleeding edge, a mainstream Intel integrated graphics, a generic Kubuntu-provided graphics driver, and so on.

More data, just thinking out loud here ...

To force a reset of the video RAM: sudo systemctl restart sddm.service
(which I have been doing)

I hate to mess with refresh rates and such (without really knowing or understanding what & why). My Kubuntu settings refresh is set at a pretty standard 60 Hz. My monitor is set at "up to 75 Hz."

inxi -Fxxx yields:

Graphics:
  Device-1: Intel vendor: ASUSTeK driver: i915 v: kernel bus ID: 00:02.0
  chip ID: 8086:9bc8
  Display: x11 server: X.Org 1.20.13 driver: modesetting unloaded: fbdev,vesa
  compositor: kwin_x11 resolution: 1920x1080~60Hz
  OpenGL: renderer: Mesa Intel UHD Graphics 630 (CML GT2) v: 4.6 Mesa 21.0.3
  direct render: Yes

[claydoh]

My monitor is set at "up to 75 Hz."

If the monitor supports 75 hz, it would be worth trying to set it to that.
If 75 is the native refresh rate, then perhaps waking from sleep it has to change from that to 60, maybe?

[Qqmike]

claydoh: If the monitor supports 75 hz, it would be worth trying to set it to that.
If 75 is the native refresh rate, then perhaps waking from sleep it has to change from that to 60, maybe?

Thanks. I can try that at some point. This is hard to test because it seems to happen so infrequently. If it becomes a bigger problem, I can change the refresh rate as an experiment. As I understand it, that is a simple matter of changing it under System Settings > Hardware > Display and Monitor, where I see that 75 Hz is listed as a drop-down option. Kind of hate to change it as I'm under the impression that 60 Hz is such a popular sweet spot for making things just right ... if you can believe what you read on the Internet, that is 🤔

(Aside, b/c I don't think I want to go here: I goofed up the links (unless I can find them somewhere, or I could google it again), but I did find one post where the user had this problem (with other AMD hardware involving an ASUS monitor). He fixed it by changing the refresh rate, using xrandr from an Arch link, which required a bit of finesse,
https://bbs.archlinux.org/viewtopic.php?id=226289
and it looks a little complicated to me.)

[Qqmike]

my output from xrandr, fyi:

display name whose refresh rate you want to modify, its target resolution, and available refresh rates. The one with asterisk (*) is the current one.

$ xrandr
Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 16384 x 16384
HDMI-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 527mm
x 296mm
  1920x1080     60.00*+  74.99    50.00    59.94  
  1920x1080i    60.00    50.00    59.94  
  1680x1050     59.88  
  1280x1024     75.02    60.02  
  1440x900      59.90  
  1280x960      60.00  
  1152x864      75.00  
  1280x720      60.00    50.00    59.94  
  1440x576      50.00  
  1024x768      75.03    70.07    60.00  
  1440x480      60.00    59.94  
  832x624       74.55  
  800x600       72.19    75.00    60.32    56.25  
  720x576       50.00  
  720x480       60.00    59.94  
  640x480       75.00    72.81    66.67    60.00    59.94  
  720x400       70.08  
DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-2 disconnected (normal left inverted right x axis y axis)

[claydoh]

You can change the refresh from System Settings

[Qqmike]

Thanks for confirming, claydoh. That's what it looks like here on 20.04, too. I'll hold off for now, to see how this thing evolves, before I go making changes. It almost seems like something "gets in there" to contaminate things only very infrequently, like once in every 100 times I wake up the PC.

Btw, the guy in that reference I lost the link to, but I copied his text, he started with this:
1680x1050 59.88 Hz* 59.95
and changed it to
1680x1050 59.88 59.95 Hz*
to solve his problem! Ha! I guess that's why he needed the surgical precision of xrandr.

59.94 is an option on my system, Post #9.

[claydoh]

 1920x1080     60.00*+  74.99    50.00    59.94

The '60' and '75' you see are actually rounded from the true figure, for clarity purposes.
You monitor is set to 60, but xrandr says 75 (74.99) is supported, you may have to look at your monitor docs to see which one is native - usually the highest value.
Setting it to 75 in System Settings won't break anything (any changes will revert to previous unless you confirm), but oddball xrandr commands might.

As to your saved post info, that person is using a very oddball resolution -1680x1050, very weird.

[Qqmike]

Your Post #12 explains and clears up some things. I will check into the monitor docs. I share the suspicion re xrandr. Many thanks for taking time to explain this stuff.

[Qqmike]

So, are you thinking or suggesting that I go ahead now, and reset the Kubuntu refresh rate to 75 and see if that prevents the flicker problem from occurring again?
Or ... wait until the flicker occurs again and then go into System Settings and change the rate to 75 to see what happens?

Btw, as far as I can tell, it appears the "native" refresh rate of that monitor is 75 Hz. I kind of had to glean this not from docs but from a 'plain English' review,
https://www.displayninja.com/asus-va24ehe-review/

[claydoh]

Yes, set it to the native 75 hz and see if it still happens.