With 6.6.x, on the CM5, PHY-level transmit hardware timestamps do not work, which means linuxptp (ptp4l) does not work. With 6.12.10, everything works fine.
I spent some time investigating the problem on 6.6.x, before I learned about rpi-update next. The first problem is that on 6.6.x packers get timestamped using the macb timestamper rather than the bcm_phy timestamper, which leads to linuxptp using a mix of two different hardware clocks. The net result is that PTP appears to work, but the synchronized time will be incorrect. More details are at https://github.com/jclark/rpi-cm4-ptp-guide/issues/39. This can be worked around on 6.6.x by turning off CONFIG_MACB_USE_HWSTAMP in the config.
After fixing this problem, another problem appears. In the bcm-phy-ptp.c, transmit hardware timestamps don't ever get generated. There is no bit set in the interrupt register saying that there is a hardware timestamp ready to be fetched. The symptom of this is that ptp4l gives "timed out while polling for tx timestamp" even after increasing increasing tx_timestamp_timeout.
These are both CM5 only problems, and are both fixed with 6.12.10.
I spent some time investigating the problem on 6.6.x, before I learned about rpi-update next. The first problem is that on 6.6.x packers get timestamped using the macb timestamper rather than the bcm_phy timestamper, which leads to linuxptp using a mix of two different hardware clocks. The net result is that PTP appears to work, but the synchronized time will be incorrect. More details are at https://github.com/jclark/rpi-cm4-ptp-guide/issues/39. This can be worked around on 6.6.x by turning off CONFIG_MACB_USE_HWSTAMP in the config.
After fixing this problem, another problem appears. In the bcm-phy-ptp.c, transmit hardware timestamps don't ever get generated. There is no bit set in the interrupt register saying that there is a hardware timestamp ready to be fetched. The symptom of this is that ptp4l gives "timed out while polling for tx timestamp" even after increasing increasing tx_timestamp_timeout.
These are both CM5 only problems, and are both fixed with 6.12.10.
Statistics: Posted by jjsea — Mon Jan 20, 2025 2:19 am