unsigned long rthal_timer_calibrate(void)
{
unsigned long v, flags;
rthal_time_t t, dt;
int i;
v = RTHAL_COMPAT_TIMERFREQ / HZ;
flags = rthal_critical_enter(NULL);
rthal_timer_program_shot(v);
t = rthal_rdtsc();
for (i = 0; i < 100; i++)
rthal_timer_program_shot(v);
dt = (rthal_rdtsc() - t);
rthal_critical_exit(flags);
#ifdef CONFIG_IPIPE_TRACE_IRQSOFF
/* Reset the max trace, since it contains the calibration time now. */
rthal_trace_max_reset();
#endif /* CONFIG_IPIPE_TRACE_IRQSOFF */
return rthal_ulldiv(dt, i + 5, NULL);
}
unsigned long rthal_timer_calibrate(void)
{
unsigned long long start, end, sum = 0, sum_sq = 0;
volatile unsigned const_delay = rthal_clockfreq_arg / HZ;
unsigned long result, flags, tsc_lat;
unsigned int delay = const_delay;
long long diff;
int i, j;
flags = rthal_critical_enter(NULL);
/*
* Hw interrupts off, other CPUs quiesced, no migration
* possible. We can now fiddle with the timer chip (per-cpu
* local or global, rthal_timer_program_shot() will handle
* this transparently via the I-pipe).
*/
steal_timer(1);
force_oneshot_hw_mode();
rthal_read_tsc(start);
barrier();
rthal_read_tsc(end);
tsc_lat = end - start;
barrier();
for (i = 0; i < RTHAL_CALIBRATE_LOOPS; i++) {
flush_cache_all();
for (j = 0; j < RTHAL_CALIBRATE_LOOPS; j++) {
rthal_read_tsc(start);
barrier();
#if IPIPE_CORE_APIREV < 2
rthal_timer_program_shot(
rthal_nodiv_imuldiv_ceil(delay, rthal_tsc_to_timer));
#else
rthal_timer_program_shot(delay);
#endif
barrier();
rthal_read_tsc(end);
diff = end - start - tsc_lat;
if (diff > 0) {
sum += diff;
sum_sq += diff * diff;
}
}
}
restore_normal_hw_mode();
rthal_critical_exit(flags);
/* Use average + standard deviation as timer programming latency. */
do_div(sum, RTHAL_CALIBRATE_LOOPS * RTHAL_CALIBRATE_LOOPS);
do_div(sum_sq, RTHAL_CALIBRATE_LOOPS * RTHAL_CALIBRATE_LOOPS);
result = sum + int_sqrt(sum_sq - sum * sum) + 1;
return result;
}
unsigned long rthal_timer_calibrate(void)
{
unsigned long flags, delay;
rthal_time_t t, dt;
int i;
delay = RTHAL_CPU_FREQ; /* 1s */
flags = rthal_critical_enter(NULL);
t = rthal_rdtsc();
for (i = 0; i < 10000; i++)
rthal_timer_program_shot(delay);
dt = rthal_rdtsc() - t;
rthal_critical_exit(flags);
return rthal_imuldiv(dt, 100000, RTHAL_CPU_FREQ);
}
