A bit late, but might be useful to others.
The Linux kernel has options to set the RTC time at boot. This will happen as
soon as the RTC probes, which is often before the rootfs mounts.
The kernel also has an option to synchronize the RTC to NTP time (userspace
provides the actual NTP) when available.
Combined this completely replaces the hwclock functionality. In fact, I found
that I had to bbappend the busybox recipeand remove the hwclock scripts, they
actually interfere with proper operation:
- At boot, the RTC clock is copied twice
- At shutdown the RTC is set. But most RTC clocks have more accurate time
keeping (e.g. temperature compensated crystal) than what the system has, so
this usually makes things worse. Better to set the RTC time from userspace and
leave it alone.
- Most RTCs have only "second" resolution and setting it too often makes it
drift more.
On 31-03-2023 00:04, Chris Elledge via lists.yoctoproject.org wrote:
I've encountered an issue when using a system that has both connman and the
hwclock.sh script enabled during startup. The default combined startup order
for these two services is wrong.
Currently connman starts at 05, and hwclock.sh is at 20 (default for
update-rc.d). This means that we have a situation where connman starts up and
obtains a correct NTP time, then hwclock.sh clobbers the system time with
whatever is in the RTC even if it is way in the past. The big issue caused by
that is connman schedules its next NTP update at an absolute time of (current
time + 1024s). Once the hwclock.sh script knocks the system time way into the
past, the NTP update will not run for a potentially very long time.
I would suggest adding a line to poky/meta/recipes-core/busybox.inc to move
hwclock.sh earlier.
For example:
INITSCRIPT_PARAMS:${PN}-hwclock = "start 04 2 3 4 5 . stop 20 0 1 6"
or
INITSCRIPT_PARAMS:${PN}-hwclock = "start 40 S . stop 20 0 1 6"
Thanks,
Chris Elledge
--
Mike Looijmans
System Expert
TOPIC Embedded Products B.V.
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