Thanks! I could now build boot.img that using UEFI+ARM-TF booting image.
Now, it showed the following messages after executing “echo mem>/sys/power/state”
[ 55.007433] PM: suspend entry 1970-01-01 03:52:14.418230201 UTC
[ 55.013407] PM: Syncing filesystems … done.
[ 55.028271] Freezing user space processes … (elapsed 0.002 seconds) done.
[ 55.038191] Freezing remaining freezable tasks … (elapsed 0.001 seconds) done.
[ 55.047252] Suspending console(s) (use no_console_suspend to debug)
However, there is system hang after it. Is it the same bug as you mentioned in https://bugs.96boards.org/show_bug.cgi?id=550 ?