BCM_PWM_CLKSRC
if (unit != BCM_PWM_CLKSRC) {
(void)bcm2835_clkman_set_frequency(sc->clkman, BCM_PWM_CLKSRC, 0);
u = bcm2835_clkman_set_frequency(sc->clkman, BCM_PWM_CLKSRC, sc->freq);