I have an EliteBook 2570p with Ubuntu GNOME 15.04 installed. When the battery is low I can suspend the computer or put it to sleep, but it wakes up right away.
For example, sometimes I am working on the laptop and the battery gets low. Instead of shutting down (which is also a critical battery level action), I prefer to take the risk that the battery runs out in sleep mode and I would like to put the computer to sleep. When I do so, it works - the screen and fan turn off, etc. - but the computer wakes up on its own after a second or two, as if nothing had happened (it has a locked screen, but doesn't pop up any errors, strange warnings, or the like).
Otherwise the sleep/suspend function works as expected. This has also been happening in 14.04 and 14.10. The computer is of course updated, maintained, and otherwise working properly. So how do I prevent this waking?
P.S.: The only idea I've got is the HP BIOS or power management chipset firmware may be making up its own mind (or lack thereof), which wouldn't be a first for HP - building laptops without Linux support for fan control and such, as it does...
Edit
~$ cat /proc/acpi/wakeup | grep enabled
EHC1 S3 *enabled pci:0000:00:1d.0
EHC2 S3 *enabled pci:0000:00:1a.0
XHC S3 *enabled pci:0000:00:14.0
~$ lspci | grep 1d
00:1d.0 USB controller: Intel Corporation 7 Series/C210 Series Chipset Family USB Enhanced Host Controller #1 (rev 04)
~$ lspci | grep 1a
00:1a.0 USB controller: Intel Corporation 7 Series/C210 Series Chipset Family USB Enhanced Host Controller #2 (rev 04)
~$ lspci | grep 14
00:14.0 USB controller: Intel Corporation 7 Series/C210 Series Chipset Family USB xHCI Host Controller (rev 04)
/proc/acpi/wakeup
) events are disabled, so it would appear it is another HP's hardware in(ter)vention. I also tried to disable "Power Monitor Circuit" in BIOS, only as an experiment, but the laptop kept waking up when the battery was low. After extensive searching the last idea is to check for clues "Wake-up Type" value withdmidecode
after such a wakeup occurs.