This test case tests freeze. This presents a general state that does not need any platform specific support. It equals frozen processes + suspended devices + idle processors. The freeze can be useful on secondary architectures (e.g. ARMs) and all platform that do not implement suspend to RAM (STR). This is a new feature introduced in kernel 3.9 and currently there is no support from user space utilities (e.g. systemd). For more details see PM_SUSPEND_FREEZE patch.
- Check that your system supports freeze:
$ cat /sys/power/state
- If there is freeze in the output, it signals that the freeze is supported. If it is not there it probably means that you have incompatible (i.e. old) kernel.
How to test
- Run the following command:
# echo freeze > /sys/power/state
- Wait until the system freezes (it typically takes several seconds).
- Wake-up your system by e.g. hitting the power button (or maybe another button depending on your HW).
- System correctly freezes.
- After wake-up system correctly resumes.
- NetworkManager re-establishes a network connection.
On ACPI platforms there are some GPEs (General Purpose Events) that are only enabled when the system is in sleep state, but aren't enabled otherwise. It means that some laptops may ignore some wake-up events when they enter the freeze state. If you cannot wake-up your laptop from the freeze, you can try to close / re-open the lid or try to issue another wake-up event. In any case please indicate this issue in the result table for us to have the overview of the current status of this feature on various hardware.