At first, I thought this issue relates to driver due to new hardware, but after a quick Google, I found out that Arch Linux user and Bionic Beaver users see the same issue. I think the answer made by monty47 is so complete that I need no further explanation. I copied his solution here including several references for my personal educational purposes.
1. Root cause and SolutionLinux Kernel supports 4 system sleep states, though some states depend on platform support codes. Those 4 states are represented by strings that can be written or read from /sys/power/state, which are
- "standby" - Power-On-Suspend
- "freeze" - Suspend-To-Idle
- "disk" - Hibernation
- s2idle - Suspend-To-Idle
- shallow - Power-on Suspend
- deep - Suspend-To-Ram
$ cat /sys/power/mem_sleep
For detailed explanation, please refer to System Power Management Sleep States by Wysocki. Only in "deep" state, all system and devices but memory are put in low-power state, and kernel might pass controls to the BIOS.
So, for my Dell XPS 9370, if I don't put it into "deep" mem sleep state, it will maintain normal "s2idle", which is just a light-weight, pure software mode. CPU will spend most of its time in idle mode, it produces heat even in this mode (because I greedily chose a Core i7 chip).
To check which mode my computer is in by default, just put it into sleep mode using Fn+End and search for sleep keyword in journal.
$ cat /sys/power/mem_sleep
[s2idle] deep # <-- highly="" in="" p="" s2idle="">$ # Fn + End to put to computer to sleep and wake it up
$ journalctl -S "2019-03-28" | grep "PM: suspend" | tail -2
Mar 28 19:08:27 ha-xps kernel: PM: suspend entry (s2idle)
Mar 28 22:29:35 ha-xps kernel: PM: suspend exit
To fix this issue, just temporarily change mem_sleep to "deep" mode by
$ echo deep | sudo tee /sys/power/mem_state
or permanently put that mode into kernel startup parameters.
$ sudo vim /etc/default/grub
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash mem_sleep_default=deep"
$ sudo grub-mkconfig -o /boot/grub/grub.cfg
$ sudo reboot
$ # Confirm after rebooted
$ sudo journalctl -b 0 | grep "PM: suspend" | tail -2
Mar 28 19:08:27 ha-xps kernel: PM: suspend entry (deep)
Mar 28 22:29:35 ha-xps kernel: PM: suspend exit -->
2. Known Related IssuesThis solution comes with 2 consequences (or related issues).
- Suspend will fails if you encrypts hard disk
- Bluetooth will not wake up after suspend. This means you cannot use bluetooth mouse after your system wakes up.
$ sudo systemctl start bluetooth
Client Characteristic Configuration
3. Future ConsiderationThis issue has not been fixed on my current Bionic HWE release.
Hope it will get fixed in upcoming version.