Hi JiaZW,
Are you using the devkit or custom board for AGX Orin?
PH.06 is used by camera currently.
If you want to use it, please remove its usage from device tree.
$ sudo cat /sys/kernel/debug/gpio|grep PH.06
gpio-397 (PH.06 |camera-control-outpu) out lo
To control GPIO through DRA, please refer to the following thread for the similar use case.
Calculating/Getting register adresses of gpio pins - #10 by KevinFFF
MDIO and MDC as GPIO in Jetson orion AGX dev Kit - #17 by KevinFFF