The tick counter on ARM is unrelated to the CPU clock

[pkhuong]

I see Platform.h assumes asm volatile("mrs %0, cntvct_el0" : "=r" (pmccntr)); returns 1/64 of the clock cycle. We can actually read the tick frequency in Hz with

__inline__ uint64_t frequency()
{
  uint32_t freq;
  asm ("mrs %0, CNTFRQ_EL0" : "=r"(freq));
  return freq;
}

That value is unfortunately unrelated to the CPU clock, but maybe we can return a consistent value like byte/ns.