Rockpi 4B+ PWM signal

How to use PWM GPIO on Rock PI 4B+ without “mraa” library.

Example: sudo echo 0 > /sys/devices/platform/ff420020.pwm/pwm/pwmchip0/export

I have not found much on pwm Rock 4, on Rockpi 3A it works for me.
Anyone know how to set the duty cycle and output on a pin?

Thanks to anyone who shares something.