Hi 1091192337,
Is it the same issue as 自定义载板，HDMI转MIPI DSI信号，背光怎么调整 - Jetson & Embedded Systems / Jetson Orin NX - NVIDIA Developer Forums?
Do you want to control PWM before kernel loaded?
If so, you may need to write custom PWM driver in UEFI for your display.
Currently, we have only PWM driver for FAN and you can refer to it.
Please check the following topic in details.
Set Fan PWM Value on Bootloder - #8 by KevinFFF