Ethernet ports shall provide same (or defined) time at the same moment or there should be a way to set their offset to 0 or desired value. IDK reboot changes the value. See steps below
Reproduction steps:
Create SD card for AM65x industrial development kit (IDK) http://www.ti.com/tool/TMDX654IDKEVM :
1) Run Ubuntu 18.04.
2) Install EA SDK 6.1 to the default location by running:
./EA ti-processor-sdk-linux-rt-am65xx-evm-06.01.00.04-Linux-x86-Install.bin
3) Insert SD card.
4) Run to create SD card script:
sudo ~/ti-processor-sdk-linux-rt-am65xx-evm-06.01.00.04/bin/create-sdcard.sh
5) choose SD card by size from the list.
6) select 2 partitions
7) select y to "Proceed anyway?" question
8) select y to "Would you like to continue?" question
9) select 1) Install pre-built images from SDK
10) select 1:tisdk-rootfs-image-am65xx-evm.tar.xz
Unpack test applications and scripts to the SD card:
11) Unpack attached file compareDirections.tar.xz the to the SD card
sudo tar xf compareDirections.tar.xz -C /media/$USER/rootfs/home/root
Setup AM65x IDK hardware image:
12) See attached image compareDirectionsSetup.jpg of the setup.
13) Insert SD card.
14) Connect two PRU ethernet interfaces on the upper board by 2 m cable.
14) Connect usb cable to UART.
16) connect power cable.
17) Switch on the IDK.
Run test scripts and applications
18) Open USB console.
19) Login as root.
20) Run:
cd compareDirections
21) Send frame from eth1 to eth3 and back and compare delays:
./compareDirections.sh eth1 eth3
You can see that the PRU ethernets has the time changed by the offset:
eth1 -> eth3 [ns]: 532
eth3 -> eth1 [ns]: 392
Average [ns]: 462.0
Difference [ns]: 140
Difference should be around 0 for PRU Ethernet with same time.If it try it again I will get similar results:
eth1 -> eth3 [ns]: 532
eth3 -> eth1 [ns]: 396
Average [ns]: 464.0
Difference [ns]: 136
Difference should be around 0 for PRU Ethernet with same time.
After IDK reboot you will get different values:
eth1 -> eth3 [ns]: 565
eth3 -> eth1 [ns]: 359
Average [ns]: 462.0
Difference [ns]: 206
Difference should be around 0 for PRU Ethernet with same time.
