Rock Pi 4 B+ Android 7.1.1 PWM Failed

Hi, I tried to export pwm0 from sysfs with (su permissions): echo 0 > /sys/class/pwm/pwmchip0/export , but nothing appears in the /sys/class/pwm/pwmchip0/ directory. ‘pwm0’ should appear.

When I check how many PWM channels are available ( cat /sys/class/pwm/pwmchip0/pwm ), I get 1.

When I check for debugging in the kernel ( cat /sys/kernel/debug/pwm ), I get this: pwm-0 (vdd-log): requested enabled period: 24997 ns duty: 0 ns polarity: inverse .

Can someone help me export the PWM?"