Thanks for the hint, this are the observations:
On 5.6:
[389399.743191] PM: suspend entry (deep)
[389399.766750] Filesystems sync: 0.023 seconds
[389399.767062] (NULL device *): firmware: direct-loading firmware
i915/kbl_dmc_ver1_04.bin
[389399.767088] (NULL device *): firmware: direct-loading firmware
intel/ibt-12-16.ddc
[389399.767167] (NULL device *): firmware: direct-loading firmware
regulatory.db
[389399.767170] (NULL device *): firmware: direct-loading firmware
regulatory.db.p7s
[389399.768870] (NULL device *): firmware: direct-loading firmware
intel/ibt-12-16.sfi
[389399.770169] (NULL device *): firmware: direct-loading firmware
iwlwifi-8265-36.ucode
[389399.770188] bbswitch: bbswitch_pm_handler: event_type=3
is_card_disabled=1 dis_before_suspend_disabled=0
[389399.770189] bbswitch: enabling discrete graphics
[389399.920138] Freezing user space processes ... (elapsed 0.004
seconds) done.
[389399.924632] OOM killer disabled.
[389399.924633] Freezing remaining freezable tasks ... (elapsed 0.001
seconds) done.
[389399.926456] printk: Suspending console(s) (use no_console_suspend to
debug)
....
[389408.348659] OOM killer enabled.
[389408.348660] Restarting tasks ... done.
[389408.428103] bbswitch: bbswitch_pm_handler: event_type=4
is_card_disabled=0 dis_before_suspend_disabled=1
[389408.428106] bbswitch: disabling discrete graphics
[389408.493000] pci 0000:01:00.0: refused to change power state from D0
to D3hot
[389408.495182] PM: suspend exit
On 5.7:
[ 89.560733] PM: suspend entry (deep)
[ 89.656060] Filesystems sync: 0.095 seconds
[ 89.656623] (NULL device *): firmware: direct-loading firmware
regulatory.db
[ 89.656630] (NULL device *): firmware: direct-loading firmware
regulatory.db.p7s
[ 89.657274] (NULL device *): firmware: direct-loading firmware
iwlwifi-8265-36.ucode
[ 89.657646] (NULL device *): firmware: direct-loading firmware
i915/kbl_dmc_ver1_04.bin
[ 89.777521] Freezing user space processes ... (elapsed 0.003 seconds)
done.
[ 89.780568] OOM killer disabled.
[ 89.780569] Freezing remaining freezable tasks ... (elapsed 0.001
seconds) done.
[ 89.782023] printk: Suspending console(s) (use no_console_suspend to
debug)
....
[ 93.238967] OOM killer enabled.
[ 93.238968] Restarting tasks ... done.
[ 93.304163] bbswitch: bbswitch_pm_handler: event_type=4
is_card_disabled=1 dis_before_suspend_disabled=0
[ 93.304165] PM: suspend exit
So to me, it seems that the suspend event is just missing.
Another, independent experiment has shown, that this missing
reactivation is the cause for the problem: Enabling the card manually
before going to suspend is a workaround for the problem.
Kind regards,
Felix
