rtc_check

1. Boot my RockPro64 without LAN and connected battery @ RTC Pins!

root@rockpro64:~# dmesg | grep rtc
[    4.798978] rk808-rtc rk808-rtc: registered as rtc0
[    4.807268] OF: graph: no port node found in /i2c@ff3d0000/typec-portc@22
[    5.032372] rk808-rtc rk808-rtc: setting system clock to 2013-01-18T14:13:22)

After bootup we do

hwclock -w

check it with
root@rockpro64:~# timedatectl
               Local time: Sat 2020-05-09 16:09:29 CEST
           Universal time: Sat 2020-05-09 14:09:29 UTC
                 RTC time: Sat 2020-05-09 14:09:30
                Time zone: Europe/Berlin (CEST, +0200)
System clock synchronized: no
              NTP service: inactive
          RTC in local TZ: no

Now we reboot.

Check time again
root@rockpro64:~# dmesg | grep rtc
[    4.804679] rk808-rtc rk808-rtc: registered as rtc0
[    4.812980] OF: graph: no port node found in /i2c@ff3d0000/typec-portc@22
[    5.059011] rk808-rtc rk808-rtc: setting system clock to 2020-05-09T14:10:27)

Now, RTC has time what we have set.