In Mint 19.3, 32bit, the problem is an external monitor / display, connected to pretty old Toshiba laptop. Not sure which forum to use. Could be hardware, or the software that isn't making it work.
EDIT 2021-12-23_for clarity.
* The added external monitor (Samsung)is a
necessity. Laptop's display has issues & often not usable (tired of fixing it).
* I'm NOT wanting 2 displays at once - I've turned off all Display Settings for laptop display. It stays off,
as long as external monitor is on.
* The external monitor works fine (even on VGA), but takes a several min. longer to wake from (kernel)
suspend & hibernate.
* Despite the native display being off in all Display settings, it still wakes instantly from
same deep suspend (S3) / hibernate, that takes the Samsung several minutes.
* Samsung starts instantly from
cold boot or restart.
* In logs, don't see (or understand?) any several minute periods or complaints about can't wake the external monitor.
* Besides this issue, the machine boots fast & runs Linux fine.
END EDIT ******
The 2nd, external Samsung monitor DID wake from suspend - some time ago, with or w/o the native 17" display enabled. So, I know it can work. When issue started, hadn't changed any GPU drivers nor any kernel or kernel firmware updates. Later, forced using Intel i915 drivers - no change. But, some other update could've caused it.
There is no BIOS update for this laptop. I played w/ a couple types of booting in BIOS- no change.
Changed to newer kernel. Orig. was 5.4.0-48. No difference.
On advice, tried disabling XFCE Pwr Mgr - no change.
I've read many dozens of long posts & articles about "external, second monitor stays black for much longer (eventually starts), when the native display starts instantly after exiting suspend mode.
NOTE: On cold boots or restarts, the Samsung starts
immediately. The problem is
after suspend (whatever is controlling it, since XFCE Power Mgr is disabled).
Don't see log entries & long elapsed times, about "Samsung" or "external monitor - not that I recognize.
If I use Suspend from Mint Settings > Suspend (has options to log off, shut down, etc), and only wait 5 - 10 min or so, it wakes instantly. So that suspend "cmd" (apparently) isn't the same as the one the kernel or something? eventually calls - I'm no expert in this area.
Might the "long suspend" be from the kernel? All options in XFCE Power Manager for suspending (or anything else) on the Samsung are turned off, zeroed, etc. Actually, in the Power Mgr file to disable it, the value is '2', so it shouldn't be doing anything. But, I see references to it in logs (not necessarily errors).
The question is, why does it take several min longer, now - not before, for external monitor to wake after the "long" suspend mode, than the native display's instant wake. Given that
in Display Settings, the native display's options are ALL off & Samsung is enabled, set as primary display.
I'm now testing if not setting either as Primary display affects it.
But, after suspend -
only when laptop is inactive for maybe 30 min. or more, the native display comes on instantly. When the Samsung finally wakes, the native display goes dark again and Samsung works fine.
When I 1st connected the Samsung, may have left the native display settings alone (it had random display issues). Don't remember waking problems back then. Something changed.
When 1st installed Mint 19.3, to speed slow booting, was told to edit a line in Grub (it made big difference). No idea if it could affect external monitors wake from suspend:
Code:
GRUB_CMDLINE_LINUX_DEFAULT="video=SVIDEO-1:d quiet splash"
.
