The "reboot" command works correctly.

There is no difference between buildroot and Debian, and the same phenomenon occurs in the latest commit of buildroot on github.

Linux Log(USB serial connected to CoreMP135 Port.C, Log in root)

$ poweroff
Stopping /etc/rc.localOK
Stopping dropbear sshd: OK
Stopping dhcpcd...
stopped /sbin/dhcpcd (pid 177)
Stopping network: OK
Stopping tee-supplicant: FAIL
Seeding 256 bits and crediting
Saving 256 bits of creditable seed for next boot
Stopping mdev... stopped process in pidfile '/var/run/mdev.pid' (pid 138)
OK
Stopping modules: rmmod: can't unload module 'soundcore': Resource temporarily unavailable
rmmod: can't unload module 'snd': Resource temporarily unavailable
rmmod: can't unload module 'snd_timer': Resource temporarily unavailable
rmmod: can't unload module 'snd_pcm': Resource temporarily unavailable
rmmod: can't unload module 'snd_pcm_dmaengine': Resource temporarily unavailable
rmmod: can't unload module 'snd_soc_core': Resource temporarily unavailable
rmmod: can't unload module 'snd_soc_simple_card_utils': Resource temporarily unavailable
rmmod: can't unload module 'libcomposite': Resource temporarily unavailable
OK
Stopping klogd: OK
Stopping syslogd: OK
umount: devtmpfs busy - remounted read-only
The system is going down NOW!
Sent SIGTERM to all processes
Sent SIGKILL to all processes
Requesting system poweroff
[  235.243319] reboot: Power down
E/TC:0   Panic at core/arch/arm/plat-stm32mp1/pm/low_power.c:405 <stm32_enter_cstop_shutdown>
E/TC:0   TEE load address @ 0xde200000
E/TC:0   Call stack:
E/TC:0    0xde203f29
E/TC:0    0xde21c0f9
E/TC:0    0xde20a5bb
E/TC:0    0xde20af21
E/TC:0    0xde23e791
E/TC:0    0xde20b233
E/TC:0    0xde20b0dc


[    0.004017] /cpus/cpu@0 missing clock-frequency property
[    0.435184] stm32-cpufreq stm32-cpufreq: OPP-v2 not supported
Starting syslogd: OK
Starting klogd: OK
Starting modules: soundcore success, snd success, snd_timer success, snd_pcm success, snd_pcm_dmaengine success, snd_soc_core success, snd_soc_simple_card_utils success, snd_soc_audio_graph_card success, snd-soc-simple-card success, snd_soc_stm32_sai success, snd_soc_stm32_sai_sub success, cdc-acm success, libcomposite success, g_serial success, OK
Running sysctl: OK
Starting mdev... OK
Seeding 256 bits and crediting
Saving 256 bits of creditable seed for next boot
Starting tee-supplicant: Using device /dev/teepriv0.
OK
Starting network: OK
Starting dhcpcd...
dhcpcd-9.4.1 starting
DUID 00:01:00:01:2d:fa:18:62:ca:7e:a7:e6:2f:fb
forked to background, child pid 1[    5.408396] m_can_platform 4400e000.can can0: bit-timing not yet defined
77
[    5.421874] m_can_platform 4400e000.can can0: failed to open can device
[    5.436986] m_can_platform 4400f000.can can1: bit-timing not yet defined
[    5.454812] m_can_platform 4400f000.can can1: failed to open can device
Starting dropbear sshd: OK
Stopping /etc/rc.localOK

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