The register values modified via busybox are limited to the current boot cycle… This was for testing only. Can you confirm if audio works for you when you program these register via busybox?
With Jetson-IO tool you don’t have to modify any DT file and re-flash it. Reboot should generally do, we can come to it later. There is an alternate way to modify the pinmux configuration. Please follow TX2 adaptation guide.
Please list the full commands you are using for playback and share the logs for me to check if there is any issue. Also please make sure you have configured the TLV codec in slave mode and Tegra I2S in master mode.