sprd_pwm_read
val = sprd_pwm_read(spc, pwm->hwpwm, SPRD_PWM_PRESCALE);
val = sprd_pwm_read(spc, pwm->hwpwm, SPRD_PWM_DUTY);
val = sprd_pwm_read(spc, pwm->hwpwm, SPRD_PWM_ENABLE);