TDA4VM: Cannot enable PPS & find it in /dev/

Hi TI Experts,

Customer and me are trying to enable PPS for J721E and faced some problems that may need your help.

SDK: 8.6 rt-Linux

Reference:

https://software-dl.ti.com/jacinto7/esd/processor-sdk-linux-jacinto7/08_06_00_11/exports/docs/linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-PTP.html?highlight=pps

Step1: add the following to the bottom of k3-j721e-common-proc-board.dts

Step 2

make all

Replace the new k3-j721e-common-proc-board.dtb & kernel image to rootfs/boot

Step 3

SD boot, but can not find /dev/pps0 or /dev/pps1

Questions:

1: May I know if there are anything else needs to be done to enable PPS? 

2: There are 2 similar example codes for Time stamp external events and PPS respectively, may I know if there is more explanation for these applications and configurations?

Thanks a lot!

Kevin