Comment 0 for bug 1926911

There is a timing issue when using the CM4 with the official CM4 IO baseboard.

The CM4 baseboard comes with a built in rtc and a battery holder by default, to enable it a devicetree overlay needs to be enabled and a matching module gets loaded ...

$ tail -2 /run/mnt/ubuntu-seed/config.txt
dtparam=i2c_vc=on
dtoverlay=i2c-rtc,pcf85063a,i2c_csi_dsi,addr=0x51

$ lsmod | grep pcf85063
rtc_pcf85063 20480 0

When booting the kernel runs hctosys about 1.5sec into the boot, the rtc module only gets loaded about 10sec later though:

$ dmesg|grep rtc
[ 1.593561] hctosys: unable to open rtc device (rtc0)
[ 10.767256] rtc-pcf85063 10-0051: registered as rtc0

Looking at the systemd journal the clock does not get set at all, only a network connection actually triggers setting of the clock (note the timestamps in the journal):

---
Apr 26 10:27:53 ubuntu kernel: mmc0: SDHCI controller on fe340000.emmc2 [fe340000.emmc2] using ADMA
Apr 26 10:27:53 ubuntu kernel: hctosys: unable to open rtc device (rtc0)
Apr 26 10:27:53 ubuntu kernel: of_cfs_init
Apr 26 10:27:53 ubuntu kernel: of_cfs_init: OK
...
Apr 26 10:28:02 CM4 systemd[1]: Started Network Name Resolution.
Apr 26 10:28:02 CM4 kernel: rtc-pcf85063 10-0051: registered as rtc0
Apr 26 10:28:02 CM4 systemd-udevd[459]: Using default interface naming scheme 'v245'.
...
Apr 26 10:28:08 CM4 avahi.daemon[593]: Registering new address record for 192.168.2.32 on wlan0.IPv4.
Apr 26 10:28:08 CM4 systemd-timesyncd[495]: Network configuration changed, trying to establish connection.
May 02 17:14:17 CM4 systemd-timesyncd[495]: Initial synchronization to time server 91.189.89.199:123 (ntp.ubu>
May 02 17:14:17 CM4 systemd[1]: Starting Online ext4 Metadata Check for All Filesystems...
---

I think the loading of the rtc_pcf85063 module should trigger an additional hctosys call ...

Just for the record, the hwclock works fine otherwise:

$ sudo hwclock
2021-05-02 19:56:11.281975+00:00