Comment 4 for bug 1349879

I've tested kernel 3.16-rc7 from mainline, with the same results.

Another thing I've tested, is disabling acpi wakeups for usb related devices: If I disable wakeup for ALL usb related devices (in my case EHC1, EHC2, XHC) suspend works correctly. Any other combination (e.g. disable only XHC and leave EHCx enabled) prevents suspending.

Attached is the dmesg output of a successful suspend/resume using this workaround.

/proc/acpi/wakeup for successful suspend looks in my case:
$ cat /proc/acpi/wakeup
Device S-state Status Sysfs node
UAR1 S4 *disabled pnp:00:0b
RP01 S4 *disabled pci:0000:00:1c.0
PXSX S4 *disabled
RP03 S4 *disabled pci:0000:00:1c.2
PXSX S4 *enabled pci:0000:03:00.0
GLAN S4 *disabled
EHC1 S4 *disabled pci:0000:00:1d.0
EHC2 S4 *disabled pci:0000:00:1a.0
XHC S4 *disabled pci:0000:00:14.0
HDEF S4 *disabled pci:0000:00:1b.0
PEG0 S4 *disabled pci:0000:00:01.0
PEGP S4 *disabled
PEG1 S4 *disabled
PEG2 S4 *disabled