Why is suspend with s2idle available on POWER8 systems?

[Paul Menzel]

Dear Linux folks,


Updating an IBM S822LC from Ubuntu 18.10 to 19.04 some user space stuff 
seems to have changed, so that going into sleep/suspend is enabled.

That raises two questions.

1.  Is suspend actually supported on a POWER8 processor?

> Apr 27 10:18:13 power NetworkManager[7534]: <info>  [1556353093.7224] manager: sleep: sleep requested (sleeping: no  e
> Apr 27 10:18:13 power systemd[1]: Reached target Sleep.
> Apr 27 10:18:13 power systemd[1]: Starting Suspend...
> Apr 27 10:18:13 power systemd-sleep[82190]: Suspending system...
> Apr 27 10:18:13 power kernel: PM: suspend entry (s2idle)
> -- Reboot --

> $ uname -m
> ppc64le
> $ more /proc/version
> Linux version 5.1.0-rc6+ (joey@power) (gcc version 8.3.0 (Ubuntu 8.3.0-6ubuntu1)) #1 SMP Sat Apr 27 10:01:48 CEST 2019
> $ more /sys/power/mem_sleep
> [s2idle]
> $ more /sys/power/state
> freeze mem
> $ grep _SUSPEND /boot/config-5.0.0-14-generic # also enabled in Ubuntuâs configuration
> CONFIG_ARCH_SUSPEND_POSSIBLE=y
> CONFIG_SUSPEND=y
> CONFIG_SUSPEND_FREEZER=y
> # CONFIG_SUSPEND_SKIP_SYNC is not set
> # CONFIG_PM_TEST_SUSPEND is not set

Should the Kconfig symbol `SUSPEND` be selectable? If yes, should their 
be some detection during runtime?

2.  If it is supported, what are the ways to getting it to resume? What 
would the IPMI command be?

For now I disabled the automatic suspend, masking the targets [1].


Kind regards,

Paul


[1]: https://wiki.debian.org/Suspend#Disable_suspend_and_hibernation