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)
