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Suffer a little bit of math every 16 second and tighten calibration of

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cpu_ticks to the low side of PPM.
This commit is contained in:
Poul-Henning Kamp 2006-03-02 08:09:46 +00:00
parent eb2ea10590
commit 301af28a06
1 changed files with 24 additions and 12 deletions
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36
sys/kern/kern_tc.c
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@ -829,6 +829,7 @@ cpu_tick_calibrate(int reset)
uint64_t c_this, c_delta;
static struct bintime t_last;
struct bintime t_this, t_delta;
uint32_t divi;
if (reset) {
/* The clock was stepped, abort & reset */
@ -846,13 +847,9 @@ cpu_tick_calibrate(int reset)
c_delta = c_this - c_last;
t_delta = t_this;
bintime_sub(&t_delta, &t_last);
if (0 && bootverbose) {
struct timespec ts;
bintime2timespec(&t_delta, &ts);
printf("%ju %ju.%016jx %ju.%09ju",
(uintmax_t)c_delta >> 4,
(uintmax_t)t_delta.sec, (uintmax_t)t_delta.frac,
(uintmax_t)ts.tv_sec, (uintmax_t)ts.tv_nsec);
if (bootverbose) {
printf("%ju.%016jx ",
(uintmax_t)t_delta.sec, (uintmax_t)t_delta.frac);
}
/*
* Validate that 16 +/- 1/256 seconds passed.
@ -862,22 +859,37 @@ cpu_tick_calibrate(int reset)
if (t_delta.sec > 16 || (
t_delta.sec == 16 && t_delta.frac >= (0x01LL << 56))) {
/* too long */
if (0 && bootverbose)
if (bootverbose)
printf("\ttoo long\n");
} else if (t_delta.sec < 15 ||
(t_delta.sec == 15 && t_delta.frac <= (0xffLL << 56))) {
/* too short */
if (0 && bootverbose)
if (bootverbose)
printf("\ttoo short\n");
} else {
/* just right */
c_delta >>= 4;
/*
* Headroom:
* 2^(64-20) / 16[s] =
* 2^(44) / 16[s] =
* 17.592.186.044.416 / 16 =
* 1.099.511.627.776 [Hz]
*/
divi = t_delta.sec << 20;
divi |= t_delta.frac >> (64 - 20);
c_delta <<= 20;
if (bootverbose)
printf(" %ju / %ju",
(uintmax_t)c_delta, (uintmax_t)divi);
c_delta /= divi;
if (bootverbose)
printf(" = %ju", c_delta);
if (c_delta > cpu_tick_frequency) {
if (0 && bootverbose)
if (bootverbose)
printf("\thigher\n");
cpu_tick_frequency = c_delta;
} else {
if (0 && bootverbose)
if (bootverbose)
printf("\tlower\n");
}
}