jetson: prevent invalid RTC from rewinding host clock#1807
Merged
brianmcgillion merged 1 commit intotiiuae:mainfrom Mar 13, 2026
Merged
jetson: prevent invalid RTC from rewinding host clock#1807brianmcgillion merged 1 commit intotiiuae:mainfrom
brianmcgillion merged 1 commit intotiiuae:mainfrom
Conversation
Contributor
There was a problem hiding this comment.
Pull request overview
This PR addresses Jetson Orin boot-time wall-clock rewinds caused by an early-registered, invalid rtc0 value by disabling kernel RTC hctosys and adding a guarded, udev-triggered time seeding path that only applies an RTC-derived time when it’s considered plausible.
Changes:
- Disable kernel
RTC_HCTOSYSfor the Jetson Orin hardware path to prevent early boot-time clock rewinds. - Add a udev-triggered
ghaf-seed-time-from-rtc@oneshot service to optionally seed system time from/sys/class/rtc/rtc0/since_epochusing plausibility checks. - Document Jetson-specific boot-time clock behavior and the intended time seeding workflow.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
| modules/reference/hardware/jetpack/nvidia-jetson-orin/jetson-orin.nix | Disables kernel hctosys and adds udev-triggered RTC seeding service with plausibility checks. |
| docs/src/content/docs/ghaf/dev/ref/build_and_run.mdx | Adds documentation note explaining Jetson RTC behavior and Ghaf’s mitigation approach. |
modules/reference/hardware/jetpack/nvidia-jetson-orin/jetson-orin.nix
Outdated
Show resolved
Hide resolved
cb6ea5c to
53f4215
Compare
Contributor
Author
|
Implemented copilot-requested safety check. |
Contributor
|
Tested on Orin AGX |
vunnyso
requested changes
Mar 11, 2026
modules/reference/hardware/jetpack/nvidia-jetson-orin/jetson-orin.nix
Outdated
Show resolved
Hide resolved
0b0c668 to
0093905
Compare
vunnyso
requested changes
Mar 12, 2026
modules/reference/hardware/jetpack/nvidia-jetson-orin/jetson-orin.nix
Outdated
Show resolved
Hide resolved
modules/reference/hardware/jetpack/nvidia-jetson-orin/jetson-orin.nix
Outdated
Show resolved
Hide resolved
modules/reference/hardware/jetpack/nvidia-jetson-orin/jetson-orin.nix
Outdated
Show resolved
Hide resolved
modules/reference/hardware/jetpack/nvidia-jetson-orin/jetson-orin.nix
Outdated
Show resolved
Hide resolved
modules/reference/hardware/jetpack/nvidia-jetson-orin/jetson-orin.nix
Outdated
Show resolved
Hide resolved
Contributor
|
Ran 'Manual Testing Steps' on Orin NX. Functionality is as expected. |
0093905 to
c6bb08d
Compare
Signed-off-by: vadik likholetov <vadikas@gmail.com>
Contributor
Author
|
Superseded by the following comment (this one was posted with shell-escaped formatting issues). |
Contributor
Author
|
Addressed all open review suggestions from the previous CHANGES_REQUESTED pass and resolved the related threads. Also squashed the branch history into a single signed commit: Validation run:
|
vunnyso
approved these changes
Mar 12, 2026
brianmcgillion
approved these changes
Mar 13, 2026
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Summary
RTC_HCTOSYS=n) for this hardware path.ghaf-seed-time-from-rtc@) that optionally seeds system time fromrtc0only when the RTC value is plausible relative to/var/lib/systemd/timesync/clock(not behind anchor, not more than 180 days ahead, and above minimum epoch).systemd-timesyncdworkflow and persisted timesync anchorWhy This Fixes Root Cause
nvvrs-pseq-rtccan register asrtc0early at boot and provide an invalid epoch-like value that rewinds wall clock time. Disabling kernel hctosys prevents this early rewind path. Time recovery remains native: optional bounded RTC seeding when rtc0 appears and then normalsystemd-timesyncdsynchronization.Manual Testing Steps
nix build .#nvidia-jetson-orin-agx-debug-from-x86_64-flash-scriptudevadm info -q property -p /sys/class/rtc/rtc0 | grep -E 'DEVNAME|SUBSYSTEM|SYSTEMD_WANTS'systemctl status ghaf-seed-time-from-rtc@rtc0.service --no-pager -ljournalctl -b -u ghaf-seed-time-from-rtc@rtc0.service --no-pagersystemctl status systemd-timesyncd.service --no-pager -lls -ld /var/lib/systemd/timesync && stat /var/lib/systemd/timesync/clocktimedatectl show -p NTPSynchronized -p TimeUSecjournalctl -b --no-pager | grep -E 'nvvrs-pseq-rtc|setting system clock|Time jumped backwards|RTC seed'Verification
On host:
rtc0:DEVNAME=/dev/rtc0SUBSYSTEM=rtcSYSTEMD_WANTS=ghaf-seed-time-from-rtc@rtc0.serviceRTC seed skipped: RTC epoch 47 below minimum 1704067200systemd-timesyncdactive and synchronized:Initial clock synchronization to Fri 2026-03-06 ... UTCNTPSynchronized=yes/var/lib/systemd/timesync/clockowned bysystemd-timesync:systemd-timesyncnvvrs-pseq-rtc ... registered as rtc0observed.setting system clock to 1970...observed in this boot.