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• For all the three cases mentioned above, the master clock could be selected by using the software BMC (Best
Master Clock) algorithm.
• The interface name and PTP device name in commands should be changed accordingly.
NOTE
4.5.5 Known issues and limitations
1. For LS1021ATSN, the Linux PTP stack only supports LS1021A Ethernet interfaces. It cannot be used for SJA1105 switch
Ethernet interfaces.
2. Packet loss issue could be observed on LS1021ATSN SGMII interfaces connected in back-to-back manner. The root cause
is that the PHY supports IEEE 802.11az EEE mode, by default. The low speed traffic makes it switch to low power mode,
which affects 1588 synchronization performance greatly.
Use the below workaround to disable this feature.
$ ifconfig eth0 up
$ ethtool --set-eee eth0 advertise 0
$ ifconfig eth0 down
$ ifconfig eth0 up
3. The ptp4l stack may report a timeout for getting the tx timestamp, but this rarely appears. This is not a bug. The stack tries
to get the tx timestamp after sending a message, but cannot get it if the driver has not completed tx timestamp processing,
in time. Just increasing the tx_timestamp_timeout parameter and re-running the stack will resolve this problem.
ptp4l[574.149]: timed out while polling for tx timestamp
ptp4l[574.152]: increasing tx_timestamp_timeout may correct this issue, but it is likely
caused by a driver bug
4.5.6 Long term test results for Linux PTP
This section describes the long term test results for Linux PTP stack implementation.
Linux PTP
Connection: back-to-back master to slave
Configuration: Sync internal is -3
Test boards: two LS1021ATSN boards, one as master and another one as slave
NXP Semiconductors
Industrial features
Open Industrial User Guide, Rev. 1.8, 05/2020
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