clocks_calc_max_nsecs
clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cycles);
cs->max_idle_ns = clocks_calc_max_nsecs(cs->mult, cs->shift,
wrap = clocks_calc_max_nsecs(new_mult, new_shift, 0, new_mask, NULL);