Orin JP5.1.1 RTC0 1970 reset

Robotics & Edge Computing Jetson & Embedded Systems Jetson AGX Orin
1

I am trying to get my 64GB AGX Orin on JP5.1.1 to use RTC0 but after a reboot the system time is incorrect and /proc/driver/rtc information conflicts with timedatectl rtc infomation.

what I have done:

Confirm JP version to show RTC0 is supported:

apt-cache show nvidia-jetpack | grep "Version"

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Confirm System is using RTC0 with Udev rule:

cat /lib/udev/rules.d/50-udev-default.rules | grep "rtc"

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I have changed this Udev rule as I don’t really want to rebuild the Kernel to change from the default rtc1 to rtc0.

Confirm system has access to rtc0 and correct symbolic link:

ls -l /dev/ | grep rtc
ls -al /dev/rtc

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This symbolic link also persist between power cycles so should always use rtc0

I then set the system time and then set the hardware clock from the current system time:

NEW_TIME="$(wget -qSO- --max-redirect=0 google.com 2>&1 | grep Date: | cut -d' ' -f5-8)Z"
sudo date -s "$NEW_TIME"
sudo hwclock -w

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timedatectl
cat /proc/driver/rtc
sudo hwclock --show

I believe this has worked as the system, RTC and hwclock all agree with each other:

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I then disconnect form the internet and power cycle the device. I then test to see if the RTC , system and hwclock are still correct:

timedatectl show

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cat /proc/driver/rtc

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sudo hwclock --show

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It looks like the hardware clock is correct after a power cycle but the system time does not automatically update from it. I am also a bit confused why /proc/driver/rtc shows 1970 or is that because this only reports rtc1? If so it would make sense.

I can then run the command hwclock -s to set the system time from the RTC and it works. I can even have this scripted so it does this automatically every reboot, but the problem is that all the time stamps at boot before this sync is done are incorrect.

so my question are:

  • How can I get the system time to automatically use the hwclock?

  • Is it possible to do this without rebuilding the kernel?

  • if I rebuild the kernel to use rtc0 by default will the system time to automatically use the hwclock?

3

I think you do have to synchronize it yourself.
If you are sure hwclock gives the right time, then it’s just that the system does not by default have a service for doing the synchronization job.

4

Ok thanks I will create a command that runs very early on to do the sync. Could you also please answer my other questions:

  • timedatectl shows the correct RTC time but /proc/driver/rtc always shows 1970 after a power cycle. Is that because timedatectl correctly uses rtc0 but /proc/driver/rtc still somehow uses rtc1. Why dose the information conflict with each other?

  • If I rebuild the kernel to use rtc0 by default will the system time automatically sync and use the hwclock or will I still need to manually do the sync myself.

5

Maybe this is not covered by the udev rule.

It’d still be the same. You have to manually sync it yourself whether you use rtc0 or rtc1.

7

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