Faulty RTC will cause various symptoms on BBGW

[acostach]

We have 2 Beaglebone Green Wireless Revision 1.0 boards. One on of them, the rtc works properly, on the other the date cannot be set, seconds don't increment, always displays 00 even after chrony got the date and time:

root@d175172:~# timedatectl
Local time: Thu 2020-03-12 13:35:42 UTC
Universal time: Thu 2020-03-12 13:35:42 UTC
RTC time: Sat 2000-01-01 00:00:00
Time zone: n/a (UTC, +0000)
System clock synchronized: yes
NTP service: n/a
RTC in local TZ: no

root@d175172:~# hwclock
Sat Jan 1 00:00:00 2000 0.000000 seconds

Various reports about this exist over the internet, many explained by the issue: oscillator not working.

The symptoms are:

• hwclock not incrementing time
• journalctl --list-boots listing a single boot on the faulty boards
• leds staying on after the board was shutdown, because the rtc did not trigger the PMIC to cut the power. In this case board needs to be unplugged manually.