After scouring google for a while I wrote this tiny script to fix the issue I have with my Lenovo S12 running Mint 17 (and apparently also present on Ubuntu 14.04).
The big symptom was that, whenever suspend was initiated, either
by closing the lid, or typing pm-suspend, or by pressing the power
button, the screen would go dark for a few seconds and then
wake up by itself.
Apparently it's caused by some USB device drivers not going into a power-saving mode or whatever, I really didn't dig that far down. Those devices prevented the kernel from completely going into suspend mode, causing the computer to wake up immediately after suspending.
It's quite simple once you know where to look.
The file /proc/acpi/wakeup contains a list of the
various devices and their status; some of them will have
an 'enabled' or a 'disabled' code on them, for example:
$ cat /proc/acpi/wakeup
Device S-state Status Sysfs node
PCI0 S5 *disabled no-bus:pci0000:00
USB0 S3 *enabled pci:0000:00:04.0
USB1 S3 *enabled pci:0000:00:04.1
USB2 S3 *enabled pci:0000:00:06.0
USB3 S3 *enabled pci:0000:00:06.1
MAC0 S5 *disabled
AZA S5 *disabled pci:0000:00:08.0
XVR3 S5 *disabled pci:0000:00:15.0
P2P0 S5 *disabled pci:0000:00:09.0
LID0 S3 *enabled platform:PNP0C0D:00
SLPB S3 *enabled platform:PNP0C0E:00
$_```
The problem devices are those that have 'enabled' next
to them.
If you `echo USB# > /proc/acpi/wakeup`, the kernel will
set the corresponding line to `disabled`, which appears
to be the appropriate state for either suspending or
hibernating.
So, the solution would be to set all `enabled` devices
to `disabled` before suspending or hibernating, and then
resetting them to `enabled` after recovering from the
power saving state.
The Script
----------
This script does exactly that: before suspending or
hibernating, it obtains a list of the `enabled` devices
and sets them to `disabled`, and saves the list
in `/var/tmp`. When returning from the power-saving
state, it'll fetch the device list and set them to
`enabled`.
Place the script in `/etc/pm/sleep.d` and set it
to mode 755.
Enjoy!
And, as expected, I disclaim any responsibility over the
consequences of using this script. I'm merely sharing this
because it worked for me, no guarantee that it will work
for you as well.
Have fun!
-gca