AM335x: MRP issue on PROFINET

Hello,

Customer reported an issue with MRP on AM3357 PROFINET.

Customer environments:
AM3357
ISDK ver.1.1.1.1
PROFINET stack ver.5.1.8.0 (provided by Molex)

Issue description:
During MRP operation, when LAN cable is disconnected, then connected again, sometimes communication cannot be recovered.

Test procedure:
Please refer to MRP_test.pdf for topology. This is based on PROFINET certification test topology.
MRP_test.pdf
1. Power-on all devices (A, B, DUT and D)
2. Wait until PROFINET cyclic communication is started.
3. Check LED on B(XF204) to confirm MRP is working and Port3 is used as main port.
4. Disconnect LAN cable from B(XF204) port3.
5. Check LED on B (XF204) to confirm Port4 is now used as main port.
6. Communication with D is recovered, but communication with DUT is not recovered sometimes.
7. Connect LAN cable to B(XF204) port3, again.
8. Disconnect LAN cable from B(XF204) port4.
9. Check LED on B (XF204) to confirm main port is back to Port3 now.
10. Communication with D is recovered, communication with DUT is also recovered.

Customer is doing debug with Molex and here are some feedbacks from their investigation.
- EtherLink down detection is working properly
- ICMP ECHO(Ping) is working properly
- LLDP transmission is working properly
- Multicast DCP cannot be received
Molex engineer thinks there may be an issue on PRU-ICSS switching operation or stack operation.

Could you try to reproduce the issue and investigate what is root cause ?

Thanks and regards,
Koichiro