Hardware PWM had open at default dtb configuration.So you need to check which Physical pin is connect to it .
Ordinary users cannot control GPIO, so they need to switch to the root user.
khadas@Khadas:~$ sudo -i
root@Khadas:~# echo 1 > /sys/class/pwm/pwmchip4/export
If you sueccess to enable it , you can see it with oscilloscope.
root@Khadas:~# echo 0 > /sys/class/pwm/pwmchip4/pwm1/enable