/dev/ptpX disappears when both ICSSG which use this clock (e.g. eth1 and eth2) interfaces are administratively down by "ip link set ethX down":
root@am65xx-evm:~# ls -al /dev/ptp*
crw------- 1 root root 247, 0 Aug 7 13:56 /dev/ptp0
crw------- 1 root root 247, 1 Aug 7 13:56 /dev/ptp1
crw------- 1 root root 247, 2 Aug 7 13:57 /dev/ptp2
crw------- 1 root root 247, 3 Aug 7 13:57 /dev/ptp3
crw------- 1 root root 247, 4 Aug 7 13:57 /dev/ptp4
root@am65xx-evm:~# ip link set eth1 down
root@am65xx-evm:~# [ 95.051309] icssg-prueth icssg0-eth eth1: Link is Down
[ 95.055842] remoteproc remoteproc2: stopped remote processor b00a000.txpru
[ 95.055866] remoteproc remoteproc1: stopped remote processor b004000.rtu
[ 95.055878] remoteproc remoteproc0: stopped remote processor b034000.pru
[ 95.076694] net eth1: stopped
[ 95.960317] icssg-prueth icssg1-eth eth5: Link is Down
root@am65xx-evm:~# ip link set eth2 down
[ 102.492420] remoteproc remoteproc5: stopped remote processor b00c000.txpru
[ 102.492452] remoteproc remoteproc4: stopped remote processor b006000.rtu
[ 102.492464] remoteproc remoteproc3: stopped remote processor b038000.pru
root@am65xx-evm:~# [ 102.512616] net eth2: stopped
root@am65xx-evm:~# ls -al /dev/ptp*
crw------- 1 root root 247, 0 Aug 7 13:56 /dev/ptp0
crw------- 1 root root 247, 1 Aug 7 13:56 /dev/ptp1
crw------- 1 root root 247, 3 Aug 7 13:57 /dev/ptp3
crw------- 1 root root 247, 4 Aug 7 13:57 /dev/ptp4
root@am65xx-evm:~#
Therefore the time synchronization needs to be restarted after each down->up and for some time ICSSG device is not synchronized to system time.
In SDK 7.x ptp device existed even when both interfaces were down,
I boot from SD card created from ti-processor-sdk-linux-rt-am65xx-evm-08_00_00_02-Linux-x86-Install.bin by
cd ti-processor-sdk-linux-rt-am65xx-evm-08_00_00_02/bin/
sudo ./mksdboot.sh --sdk .. --device /dev/sdd
