通过示波器量了PWM0的波形图，波形图不是方波，以下是pwm的信息，请问大牛问题出在哪里了?
firefly@firefly:~/Desktop$ cat /sys/kernel/debug/pwm
platform/ff680030.pwm, 1 PWM device
pwm-0 (pwm3 ): requested period: 0 ns duty: 0 ns polarity: inverse
platform/ff680020.pwm, 1 PWM device
pwm-0 (pwm2 ): requested period: 0 ns duty: 0 ns polarity: inverse
platform/ff680010.pwm, 1 PWM device
pwm-0 ((null) ): period: 0 ns duty: 0 ns polarity: inverse
platform/ff680000.pwm, 1 PWM device
pwm-0 (pwm0 ): requested enabled period: 1000000 ns duty: 500000 ns polarity: inverse