Regression in Suspend functionality

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Ubuntu Version: 24.04.3 LTS

Desktop Environment (if applicable):
LXQt

Problem Description:
When I suspend the computer, it may or may not be able to wake up. That used to work reliably but broke when I allowed the installation of updates/upgrades after months of uptime (interrupted only by suspend-resume cycles). Therefore the word “regression” in the topic.
Two lines from the list of boots show the long uptime and change in kernel versions:

Sun Dec 14 22:26 6.8.0-90-generic
Wed Aug 20 23:33 6.8.0-71-generic

For suspending I use either the “moon” button on the keyboard or by the “Suspend” item in the menu of the LXQt desktop.

I remember that some similar breaking of the suspend functionality did happen in some past years. That time, the problem got fixed by some later update.

Relevant System Information:
Processor: AMD Athlon Silver 3050U with Radeon Graphics
This is a (small) desktop computer, the model name being something like “HP Slim”.

What I’ve Tried:

  • I tried different settings of screen saver and switching off the screen saver. Why that seemed to make some sense: When I give the click or press to suspend , the screen usually plays a screensaver for some time before actually suspending.
  • I tried booting in recovery mode, to no avail.

… Thanks for any help!

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This really looks like a kernel regression, especially since suspend worked reliably on 6.8.0-71 and broke after upgrading to 6.8.0-90.

A good first test is to boot an older kernel from Advanced options in GRUB and see if suspend works again. If it does, that confirms the regression.

On AMD systems, another well-known fix is forcing deep sleep:
mem_sleep_default=deep

LXQt is very unlikely to be the cause here — this is almost certainly kernel/ACPI related.

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Thanks for your hints, MesterPerfect! It indeed seems to work with the older kernel (6.8.0-71). :+1:

When I read the mem_sleep (pseudo-)file like “cat /sys/power/mem_sleep”, I get “s2idle [deep]”. So it seems that the “deep” option is already selected.

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