Comment # 8 on bug 1222345 from Takashi Iwai

Then some spurious interrupt must be waking up the machine.
Please check the following:

- Enable/disable LID ACPI:
  To check the status:
    % cat /proc/acpi/wakeup
  To toggle the status:
    % echo LID > /proc/acpi/wakeup

If this doesn't influence, it's something else than ACPI wakeup.

Then, you can try the direct suspend by
  echo mem > /sys/power/state
Does it behave differently?