in core.c [321:333]
static void mux_control_delay(struct mux_control *mux, unsigned int delay_us)
{
ktime_t delayend;
s64 remaining;
if (!delay_us)
return;
delayend = ktime_add_us(mux->last_change, delay_us);
remaining = ktime_us_delta(delayend, ktime_get());
if (remaining > 0)
fsleep(remaining);
}