Customer is testing PTP Operator on OpenShift Container Platform 4.20.4 (fresh installation) using Intel E810 NIC with ZED-F9T GNSS module in T-GM configuration.

The linuxptp-daemon internally executes ubxtool commands to enable NMEA and disable BINARY mode. Operator logs show successful execution:

Enable NMEA
disable binary

No "error executing ubxtool command" messages are present.

However, despite success logs, the GNSS module sometimes remains in binary-only mode. When this occurs, ts2phc fails with:

nmea: no valid rmc fix
source ts not valid

Customer confirmed that when explicitly defining the same ubxtool commands in PtpConfig under ublxCmds, including additional flags (-v 1 -w 2), the GNSS mode switches correctly and time synchronization works reliably.

This suggests the internal ubxtool invocation may be missing required flags or there may be a timing/race condition during initialization.

Version-Release number of selected component (if applicable):
PTP Operator on OpenShift Container Platform 4.20.4

How reproducible:
Intermittent on specific server hardware. Reproducible when GNSS module is manually set to binary-only mode and PtpConfig is applied without explicit ublxCmds including -v 1 -w 2 flags.

Steps to Reproduce:
1. Deploy OpenShift 4.20.4 on bare metal with Intel E810 + ZED-F9T GNSS.
2. Configure PTP Operator in T-GM mode without explicit ublxCmds.
3. Ensure GNSS module is in binary-only mode.
4. Apply PtpConfig and observe linuxptp-daemon logs.
5. Observe ts2phc errors: "nmea: no valid rmc fix" and "source ts not valid".

Actual results:

Operator logs indicate successful execution of Enable NMEA and disable binary commands, but GNSS remains in binary-only mode and ts2phc fails to receive valid NMEA data.

Expected results:

When linuxptp-daemon logs show successful execution of Enable NMEA and disable binary, the GNSS module should reliably switch to NMEA mode and ts2phc should receive valid RMC messages.

Additional info:

Workaround: explicitly define ubxtool commands in PtpConfig with flags:

-v 1 -w 2 -P 29.20 -e NMEA
-v 1 -w 2 -P 29.20 -d BINARY

When these are included, GNSS mode switches correctly and synchronization works.

This is a fresh 4.20.4 installation (not an upgrade). Not reproducible on all tested servers with similar hardware.