PROCESSOR-SDK-J721E: enable low power mode (freeze, suspend, etc.) on j721e board

Tool/software:

Hello,

I am wondered about how to enter low power mode on j721e.

1. I have tried "systemctl suspend".  And it just returned a prompt and no response.

  When I tried "journalctl -xe | grep suspend", the log was

Dec 03 03:04 : 19 j721e - evm sudo[1266] : root : TTY = pts / 0; PWD = / home / root; USER = root; COMMAND = / bin / systemctl suspend --test
Dec 03 04:04 : 21 j721e - evm sudo[1308] : root : TTY = pts / 0; PWD = / home / root; USER = root; COMMAND = / bin / systemctl suspend --no - block
Dec 03 04:04 : 21 j721e - evm systemd - sleep[1311] : Entering sleep state 'suspend'...
Dec 03 04 : 04 : 21 j721e - evm kernel : PM: suspend entry(s2idle)
Dec 03 04 : 04 : 21 j721e - evm kernel : PM: suspend exit
Dec 03 04 : 04 : 21 j721e - evm kernel : PM: suspend entry(s2idle)
Dec 03 04 : 04 : 21 j721e - evm kernel : PM: suspend exit
Dec 03 04 : 04 : 21 j721e - evm systemd[1] : systemd - suspend.service : Main process exited, code = exited, status = 1 / FAILURE
Dec 03 04 : 04 : 21 j721e - evm systemd[1] : systemd - suspend.service : Failed with result 'exit-code'.
Dec 03 04 : 04 : 21 j721e - evm systemd[1] : suspend.target : Job suspend.target / start failed with result 'dependency'

2. When I tired "echo freeze > /sys/power/state"

An error: -sh: echo: write error: Operation not permitted

is shown.

Is there anything I can try to make the low power mode (freeze, suspend, hibernate) ?

Thanks for your help in advance.

Dalsoo