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freebsd/sys/kern/kern_tc.c

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/*-
* ----------------------------------------------------------------------------
* "THE BEER-WARE LICENSE" (Revision 42):
* <phk@FreeBSD.ORG> wrote this file. As long as you retain this notice you
* can do whatever you want with this stuff. If we meet some day, and you think
* this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp
* ----------------------------------------------------------------------------
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_ntp.h"
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <sys/systm.h>
#include <sys/timepps.h>
#include <sys/timetc.h>
#include <sys/timex.h>
/*
* A large step happens on boot. This constant detects such steps.
* It is relatively small so that ntp_update_second gets called enough
* in the typical 'missed a couple of seconds' case, but doesn't loop
* forever when the time step is large.
*/
#define LARGE_STEP 200
/*
* Implement a dummy timecounter which we can use until we get a real one
* in the air. This allows the console and other early stuff to use
* time services.
*/
static u_int
dummy_get_timecount(struct timecounter *tc)
{
static u_int now;
return (++now);
}
static struct timecounter dummy_timecounter = {
dummy_get_timecount, 0, ~0u, 1000000, "dummy", -1000000
};
struct timehands {
/* These fields must be initialized by the driver. */
struct timecounter *th_counter;
int64_t th_adjustment;
u_int64_t th_scale;
u_int th_offset_count;
struct bintime th_offset;
struct timeval th_microtime;
struct timespec th_nanotime;
/* Fields not to be copied in tc_windup start with th_generation. */
volatile u_int th_generation;
struct timehands *th_next;
};
static struct timehands th0;
static struct timehands th9 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th0};
static struct timehands th8 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th9};
static struct timehands th7 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th8};
static struct timehands th6 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th7};
static struct timehands th5 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th6};
static struct timehands th4 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th5};
static struct timehands th3 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th4};
static struct timehands th2 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th3};
static struct timehands th1 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th2};
static struct timehands th0 = {
&dummy_timecounter,
0,
(uint64_t)-1 / 1000000,
0,
{1, 0},
{0, 0},
{0, 0},
1,
&th1
};
static struct timehands *volatile timehands = &th0;
struct timecounter *timecounter = &dummy_timecounter;
static struct timecounter *timecounters = &dummy_timecounter;
time_t time_second = 1;
time_t time_uptime = 1;
static struct bintime boottimebin;
struct timeval boottime;
static int sysctl_kern_boottime(SYSCTL_HANDLER_ARGS);
SYSCTL_PROC(_kern, KERN_BOOTTIME, boottime, CTLTYPE_STRUCT|CTLFLAG_RD,
NULL, 0, sysctl_kern_boottime, "S,timeval", "System boottime");
SYSCTL_NODE(_kern, OID_AUTO, timecounter, CTLFLAG_RW, 0, "");
static int timestepwarnings;
SYSCTL_INT(_kern_timecounter, OID_AUTO, stepwarnings, CTLFLAG_RW,
&timestepwarnings, 0, "");
#define TC_STATS(foo) \
static u_int foo; \
SYSCTL_UINT(_kern_timecounter, OID_AUTO, foo, CTLFLAG_RD, &foo, 0, "");\
struct __hack
TC_STATS(nbinuptime); TC_STATS(nnanouptime); TC_STATS(nmicrouptime);
TC_STATS(nbintime); TC_STATS(nnanotime); TC_STATS(nmicrotime);
TC_STATS(ngetbinuptime); TC_STATS(ngetnanouptime); TC_STATS(ngetmicrouptime);
TC_STATS(ngetbintime); TC_STATS(ngetnanotime); TC_STATS(ngetmicrotime);
TC_STATS(nsetclock);
#undef TC_STATS
static void tc_windup(void);
static void cpu_tick_calibrate(int);
static int
sysctl_kern_boottime(SYSCTL_HANDLER_ARGS)
{
#ifdef SCTL_MASK32
int tv[2];
if (req->flags & SCTL_MASK32) {
tv[0] = boottime.tv_sec;
tv[1] = boottime.tv_usec;
return SYSCTL_OUT(req, tv, sizeof(tv));
} else
#endif
return SYSCTL_OUT(req, &boottime, sizeof(boottime));
}
/*
* Return the difference between the timehands' counter value now and what
* was when we copied it to the timehands' offset_count.
*/
static __inline u_int
tc_delta(struct timehands *th)
{
struct timecounter *tc;
tc = th->th_counter;
return ((tc->tc_get_timecount(tc) - th->th_offset_count) &
tc->tc_counter_mask);
}
/*
* Functions for reading the time. We have to loop until we are sure that
* the timehands that we operated on was not updated under our feet. See
* the comment in <sys/time.h> for a description of these 12 functions.
*/
void
binuptime(struct bintime *bt)
{
struct timehands *th;
u_int gen;
nbinuptime++;
do {
th = timehands;
gen = th->th_generation;
*bt = th->th_offset;
bintime_addx(bt, th->th_scale * tc_delta(th));
} while (gen == 0 || gen != th->th_generation);
}
void
nanouptime(struct timespec *tsp)
{
struct bintime bt;
nnanouptime++;
binuptime(&bt);
bintime2timespec(&bt, tsp);
}
void
microuptime(struct timeval *tvp)
{
struct bintime bt;
nmicrouptime++;
binuptime(&bt);
bintime2timeval(&bt, tvp);
}
void
bintime(struct bintime *bt)
{
nbintime++;
binuptime(bt);
bintime_add(bt, &boottimebin);
}
void
nanotime(struct timespec *tsp)
{
struct bintime bt;
nnanotime++;
bintime(&bt);
bintime2timespec(&bt, tsp);
}
void
microtime(struct timeval *tvp)
{
struct bintime bt;
nmicrotime++;
bintime(&bt);
bintime2timeval(&bt, tvp);
}
void
getbinuptime(struct bintime *bt)
{
struct timehands *th;
u_int gen;
ngetbinuptime++;
do {
th = timehands;
gen = th->th_generation;
*bt = th->th_offset;
} while (gen == 0 || gen != th->th_generation);
}
void
getnanouptime(struct timespec *tsp)
{
struct timehands *th;
u_int gen;
ngetnanouptime++;
do {
th = timehands;
gen = th->th_generation;
bintime2timespec(&th->th_offset, tsp);
} while (gen == 0 || gen != th->th_generation);
}
void
getmicrouptime(struct timeval *tvp)
{
struct timehands *th;
u_int gen;
ngetmicrouptime++;
do {
th = timehands;
gen = th->th_generation;
bintime2timeval(&th->th_offset, tvp);
} while (gen == 0 || gen != th->th_generation);
}
void
getbintime(struct bintime *bt)
{
struct timehands *th;
u_int gen;
ngetbintime++;
do {
th = timehands;
gen = th->th_generation;
*bt = th->th_offset;
} while (gen == 0 || gen != th->th_generation);
bintime_add(bt, &boottimebin);
}
void
getnanotime(struct timespec *tsp)
{
struct timehands *th;
u_int gen;
ngetnanotime++;
do {
th = timehands;
gen = th->th_generation;
*tsp = th->th_nanotime;
} while (gen == 0 || gen != th->th_generation);
}
void
getmicrotime(struct timeval *tvp)
{
struct timehands *th;
u_int gen;
ngetmicrotime++;
do {
th = timehands;
gen = th->th_generation;
*tvp = th->th_microtime;
} while (gen == 0 || gen != th->th_generation);
}
/*
* Initialize a new timecounter and possibly use it.
*/
void
tc_init(struct timecounter *tc)
{
u_int u;
u = tc->tc_frequency / tc->tc_counter_mask;
/* XXX: We need some margin here, 10% is a guess */
u *= 11;
u /= 10;
if (u > hz && tc->tc_quality >= 0) {
tc->tc_quality = -2000;
if (bootverbose) {
printf("Timecounter \"%s\" frequency %ju Hz",
tc->tc_name, (uintmax_t)tc->tc_frequency);
printf(" -- Insufficient hz, needs at least %u\n", u);
}
} else if (tc->tc_quality >= 0 || bootverbose) {
printf("Timecounter \"%s\" frequency %ju Hz quality %d\n",
tc->tc_name, (uintmax_t)tc->tc_frequency,
tc->tc_quality);
}
tc->tc_next = timecounters;
timecounters = tc;
/*
* Never automatically use a timecounter with negative quality.
* Even though we run on the dummy counter, switching here may be
* worse since this timecounter may not be monotonous.
*/
if (tc->tc_quality < 0)
return;
if (tc->tc_quality < timecounter->tc_quality)
return;
if (tc->tc_quality == timecounter->tc_quality &&
tc->tc_frequency < timecounter->tc_frequency)
return;
(void)tc->tc_get_timecount(tc);
(void)tc->tc_get_timecount(tc);
timecounter = tc;
}
/* Report the frequency of the current timecounter. */
u_int64_t
tc_getfrequency(void)
{
return (timehands->th_counter->tc_frequency);
}
/*
* Step our concept of UTC. This is done by modifying our estimate of
* when we booted.
* XXX: not locked.
*/
void
tc_setclock(struct timespec *ts)
{
struct timespec tbef, taft;
struct bintime bt, bt2;
cpu_tick_calibrate(1);
nsetclock++;
nanotime(&tbef);
timespec2bintime(ts, &bt);
binuptime(&bt2);
bintime_sub(&bt, &bt2);
bintime_add(&bt2, &boottimebin);
boottimebin = bt;
bintime2timeval(&bt, &boottime);
/* XXX fiddle all the little crinkly bits around the fiords... */
tc_windup();
nanotime(&taft);
if (timestepwarnings) {
log(LOG_INFO,
"Time stepped from %jd.%09ld to %jd.%09ld (%jd.%09ld)\n",
(intmax_t)tbef.tv_sec, tbef.tv_nsec,
(intmax_t)taft.tv_sec, taft.tv_nsec,
(intmax_t)ts->tv_sec, ts->tv_nsec);
}
cpu_tick_calibrate(1);
}
/*
* Initialize the next struct timehands in the ring and make
* it the active timehands. Along the way we might switch to a different
* timecounter and/or do seconds processing in NTP. Slightly magic.
*/
static void
tc_windup(void)
{
struct bintime bt;
struct timehands *th, *tho;
u_int64_t scale;
u_int delta, ncount, ogen;
int i;
time_t t;
/*
* Make the next timehands a copy of the current one, but do not
* overwrite the generation or next pointer. While we update
* the contents, the generation must be zero.
*/
tho = timehands;
th = tho->th_next;
ogen = th->th_generation;
th->th_generation = 0;
bcopy(tho, th, offsetof(struct timehands, th_generation));
/*
* Capture a timecounter delta on the current timecounter and if
* changing timecounters, a counter value from the new timecounter.
* Update the offset fields accordingly.
*/
delta = tc_delta(th);
if (th->th_counter != timecounter)
ncount = timecounter->tc_get_timecount(timecounter);
else
ncount = 0;
th->th_offset_count += delta;
th->th_offset_count &= th->th_counter->tc_counter_mask;
bintime_addx(&th->th_offset, th->th_scale * delta);
/*
* Hardware latching timecounters may not generate interrupts on
* PPS events, so instead we poll them. There is a finite risk that
* the hardware might capture a count which is later than the one we
* got above, and therefore possibly in the next NTP second which might
* have a different rate than the current NTP second. It doesn't
* matter in practice.
*/
if (tho->th_counter->tc_poll_pps)
tho->th_counter->tc_poll_pps(tho->th_counter);
/*
* Deal with NTP second processing. The for loop normally
* iterates at most once, but in extreme situations it might
* keep NTP sane if timeouts are not run for several seconds.
* At boot, the time step can be large when the TOD hardware
* has been read, so on really large steps, we call
* ntp_update_second only twice. We need to call it twice in
* case we missed a leap second.
*/
bt = th->th_offset;
bintime_add(&bt, &boottimebin);
i = bt.sec - tho->th_microtime.tv_sec;
if (i > LARGE_STEP)
i = 2;
for (; i > 0; i--) {
t = bt.sec;
ntp_update_second(&th->th_adjustment, &bt.sec);
if (bt.sec != t)
boottimebin.sec += bt.sec - t;
}
/* Update the UTC timestamps used by the get*() functions. */
/* XXX shouldn't do this here. Should force non-`get' versions. */
bintime2timeval(&bt, &th->th_microtime);
bintime2timespec(&bt, &th->th_nanotime);
/* Now is a good time to change timecounters. */
if (th->th_counter != timecounter) {
th->th_counter = timecounter;
th->th_offset_count = ncount;
}
/*-
* Recalculate the scaling factor. We want the number of 1/2^64
* fractions of a second per period of the hardware counter, taking
* into account the th_adjustment factor which the NTP PLL/adjtime(2)
* processing provides us with.
*
* The th_adjustment is nanoseconds per second with 32 bit binary
* fraction and we want 64 bit binary fraction of second:
*
* x = a * 2^32 / 10^9 = a * 4.294967296
*
* The range of th_adjustment is +/- 5000PPM so inside a 64bit int
* we can only multiply by about 850 without overflowing, that
* leaves no suitably precise fractions for multiply before divide.
*
* Divide before multiply with a fraction of 2199/512 results in a
* systematic undercompensation of 10PPM of th_adjustment. On a
* 5000PPM adjustment this is a 0.05PPM error. This is acceptable.
*
* We happily sacrifice the lowest of the 64 bits of our result
* to the goddess of code clarity.
*
*/
scale = (u_int64_t)1 << 63;
scale += (th->th_adjustment / 1024) * 2199;
scale /= th->th_counter->tc_frequency;
th->th_scale = scale * 2;
/*
* Now that the struct timehands is again consistent, set the new
* generation number, making sure to not make it zero.
*/
if (++ogen == 0)
ogen = 1;
th->th_generation = ogen;
/* Go live with the new struct timehands. */
time_second = th->th_microtime.tv_sec;
time_uptime = th->th_offset.sec;
timehands = th;
}
/* Report or change the active timecounter hardware. */
static int
sysctl_kern_timecounter_hardware(SYSCTL_HANDLER_ARGS)
{
char newname[32];
struct timecounter *newtc, *tc;
int error;
tc = timecounter;
strlcpy(newname, tc->tc_name, sizeof(newname));
error = sysctl_handle_string(oidp, &newname[0], sizeof(newname), req);
if (error != 0 || req->newptr == NULL ||
strcmp(newname, tc->tc_name) == 0)
return (error);
for (newtc = timecounters; newtc != NULL; newtc = newtc->tc_next) {
if (strcmp(newname, newtc->tc_name) != 0)
continue;
/* Warm up new timecounter. */
(void)newtc->tc_get_timecount(newtc);
(void)newtc->tc_get_timecount(newtc);
timecounter = newtc;
return (0);
}
return (EINVAL);
}
SYSCTL_PROC(_kern_timecounter, OID_AUTO, hardware, CTLTYPE_STRING | CTLFLAG_RW,
0, 0, sysctl_kern_timecounter_hardware, "A", "");
/* Report or change the active timecounter hardware. */
static int
sysctl_kern_timecounter_choice(SYSCTL_HANDLER_ARGS)
{
char buf[32], *spc;
struct timecounter *tc;
int error;
spc = "";
error = 0;
for (tc = timecounters; error == 0 && tc != NULL; tc = tc->tc_next) {
sprintf(buf, "%s%s(%d)",
spc, tc->tc_name, tc->tc_quality);
error = SYSCTL_OUT(req, buf, strlen(buf));
spc = " ";
}
return (error);
}
SYSCTL_PROC(_kern_timecounter, OID_AUTO, choice, CTLTYPE_STRING | CTLFLAG_RD,
0, 0, sysctl_kern_timecounter_choice, "A", "");
/*
* RFC 2783 PPS-API implementation.
*/
int
pps_ioctl(u_long cmd, caddr_t data, struct pps_state *pps)
{
pps_params_t *app;
struct pps_fetch_args *fapi;
#ifdef PPS_SYNC
struct pps_kcbind_args *kapi;
#endif
KASSERT(pps != NULL, ("NULL pps pointer in pps_ioctl"));
switch (cmd) {
case PPS_IOC_CREATE:
return (0);
case PPS_IOC_DESTROY:
return (0);
case PPS_IOC_SETPARAMS:
app = (pps_params_t *)data;
if (app->mode & ~pps->ppscap)
return (EINVAL);
pps->ppsparam = *app;
return (0);
case PPS_IOC_GETPARAMS:
app = (pps_params_t *)data;
*app = pps->ppsparam;
app->api_version = PPS_API_VERS_1;
return (0);
case PPS_IOC_GETCAP:
*(int*)data = pps->ppscap;
return (0);
case PPS_IOC_FETCH:
fapi = (struct pps_fetch_args *)data;
if (fapi->tsformat && fapi->tsformat != PPS_TSFMT_TSPEC)
return (EINVAL);
if (fapi->timeout.tv_sec || fapi->timeout.tv_nsec)
return (EOPNOTSUPP);
pps->ppsinfo.current_mode = pps->ppsparam.mode;
fapi->pps_info_buf = pps->ppsinfo;
return (0);
case PPS_IOC_KCBIND:
#ifdef PPS_SYNC
kapi = (struct pps_kcbind_args *)data;
/* XXX Only root should be able to do this */
if (kapi->tsformat && kapi->tsformat != PPS_TSFMT_TSPEC)
return (EINVAL);
if (kapi->kernel_consumer != PPS_KC_HARDPPS)
return (EINVAL);
if (kapi->edge & ~pps->ppscap)
return (EINVAL);
pps->kcmode = kapi->edge;
return (0);
#else
return (EOPNOTSUPP);
#endif
default:
return (ENOIOCTL);
}
}
void
pps_init(struct pps_state *pps)
{
pps->ppscap |= PPS_TSFMT_TSPEC;
if (pps->ppscap & PPS_CAPTUREASSERT)
pps->ppscap |= PPS_OFFSETASSERT;
if (pps->ppscap & PPS_CAPTURECLEAR)
pps->ppscap |= PPS_OFFSETCLEAR;
}
void
pps_capture(struct pps_state *pps)
{
struct timehands *th;
KASSERT(pps != NULL, ("NULL pps pointer in pps_capture"));
th = timehands;
pps->capgen = th->th_generation;
pps->capth = th;
pps->capcount = th->th_counter->tc_get_timecount(th->th_counter);
if (pps->capgen != th->th_generation)
pps->capgen = 0;
}
void
pps_event(struct pps_state *pps, int event)
{
struct bintime bt;
struct timespec ts, *tsp, *osp;
u_int tcount, *pcount;
int foff, fhard;
pps_seq_t *pseq;
KASSERT(pps != NULL, ("NULL pps pointer in pps_event"));
/* If the timecounter was wound up underneath us, bail out. */
if (pps->capgen == 0 || pps->capgen != pps->capth->th_generation)
return;
/* Things would be easier with arrays. */
if (event == PPS_CAPTUREASSERT) {
tsp = &pps->ppsinfo.assert_timestamp;
osp = &pps->ppsparam.assert_offset;
foff = pps->ppsparam.mode & PPS_OFFSETASSERT;
fhard = pps->kcmode & PPS_CAPTUREASSERT;
pcount = &pps->ppscount[0];
pseq = &pps->ppsinfo.assert_sequence;
} else {
tsp = &pps->ppsinfo.clear_timestamp;
osp = &pps->ppsparam.clear_offset;
foff = pps->ppsparam.mode & PPS_OFFSETCLEAR;
fhard = pps->kcmode & PPS_CAPTURECLEAR;
pcount = &pps->ppscount[1];
pseq = &pps->ppsinfo.clear_sequence;
}
/*
* If the timecounter changed, we cannot compare the count values, so
* we have to drop the rest of the PPS-stuff until the next event.
*/
if (pps->ppstc != pps->capth->th_counter) {
pps->ppstc = pps->capth->th_counter;
*pcount = pps->capcount;
pps->ppscount[2] = pps->capcount;
return;
}
/* Convert the count to a timespec. */
tcount = pps->capcount - pps->capth->th_offset_count;
tcount &= pps->capth->th_counter->tc_counter_mask;
bt = pps->capth->th_offset;
bintime_addx(&bt, pps->capth->th_scale * tcount);
bintime_add(&bt, &boottimebin);
bintime2timespec(&bt, &ts);
/* If the timecounter was wound up underneath us, bail out. */
if (pps->capgen != pps->capth->th_generation)
return;
*pcount = pps->capcount;
(*pseq)++;
*tsp = ts;
if (foff) {
timespecadd(tsp, osp);
if (tsp->tv_nsec < 0) {
tsp->tv_nsec += 1000000000;
tsp->tv_sec -= 1;
}
}
#ifdef PPS_SYNC
if (fhard) {
u_int64_t scale;
/*
* Feed the NTP PLL/FLL.
* The FLL wants to know how many (hardware) nanoseconds
* elapsed since the previous event.
*/
tcount = pps->capcount - pps->ppscount[2];
pps->ppscount[2] = pps->capcount;
tcount &= pps->capth->th_counter->tc_counter_mask;
scale = (u_int64_t)1 << 63;
scale /= pps->capth->th_counter->tc_frequency;
scale *= 2;
bt.sec = 0;
bt.frac = 0;
bintime_addx(&bt, scale * tcount);
bintime2timespec(&bt, &ts);
hardpps(tsp, ts.tv_nsec + 1000000000 * ts.tv_sec);
}
#endif
}
/*
* Timecounters need to be updated every so often to prevent the hardware
* counter from overflowing. Updating also recalculates the cached values
* used by the get*() family of functions, so their precision depends on
* the update frequency.
*/
static int tc_tick;
SYSCTL_INT(_kern_timecounter, OID_AUTO, tick, CTLFLAG_RD, &tc_tick, 0, "");
void
tc_ticktock(void)
{
static int count;
static time_t last_calib;
if (++count < tc_tick)
return;
count = 0;
tc_windup();
if (time_uptime != last_calib && !(time_uptime & 0xf)) {
cpu_tick_calibrate(0);
last_calib = time_uptime;
}
}
static void
inittimecounter(void *dummy)
{
u_int p;
/*
* Set the initial timeout to
* max(1, <approx. number of hardclock ticks in a millisecond>).
* People should probably not use the sysctl to set the timeout
* to smaller than its inital value, since that value is the
* smallest reasonable one. If they want better timestamps they
* should use the non-"get"* functions.
*/
if (hz > 1000)
tc_tick = (hz + 500) / 1000;
else
tc_tick = 1;
p = (tc_tick * 1000000) / hz;
printf("Timecounters tick every %d.%03u msec\n", p / 1000, p % 1000);
/* warm up new timecounter (again) and get rolling. */
(void)timecounter->tc_get_timecount(timecounter);
(void)timecounter->tc_get_timecount(timecounter);
}
SYSINIT(timecounter, SI_SUB_CLOCKS, SI_ORDER_SECOND, inittimecounter, NULL)
/* Cpu tick handling -------------------------------------------------*/
static int cpu_tick_variable;
static uint64_t cpu_tick_frequency;
static uint64_t
tc_cpu_ticks(void)
{
static uint64_t base;
static unsigned last;
unsigned u;
struct timecounter *tc;
tc = timehands->th_counter;
u = tc->tc_get_timecount(tc) & tc->tc_counter_mask;
if (u < last)
base += (uint64_t)tc->tc_counter_mask + 1;
last = u;
return (u + base);
}
/*
* This function gets called ever 16 seconds on only one designated
* CPU in the system from hardclock() via tc_ticktock().
*
* Whenever the real time clock is stepped we get called with reset=1
* to make sure we handle suspend/resume and similar events correctly.
*/
static void
cpu_tick_calibrate(int reset)
{
static uint64_t c_last;
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 */
t_last.sec = 0;
return;
}
/* we don't calibrate fixed rate cputicks */
if (!cpu_tick_variable)
return;
getbinuptime(&t_this);
c_this = cpu_ticks();
if (t_last.sec != 0) {
c_delta = c_this - c_last;
t_delta = t_this;
bintime_sub(&t_delta, &t_last);
/*
* Validate that 16 +/- 1/256 seconds passed.
* After division by 16 this gives us a precision of
* roughly 250PPM which is sufficient
*/
if (t_delta.sec > 16 || (
t_delta.sec == 16 && t_delta.frac >= (0x01LL << 56))) {
/* too long */
if (bootverbose)
printf("%ju.%016jx too long\n",
(uintmax_t)t_delta.sec,
(uintmax_t)t_delta.frac);
} else if (t_delta.sec < 15 ||
(t_delta.sec == 15 && t_delta.frac <= (0xffLL << 56))) {
/* too short */
if (bootverbose)
printf("%ju.%016jx too short\n",
(uintmax_t)t_delta.sec,
(uintmax_t)t_delta.frac);
} else {
/* just right */
/*
* 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;
c_delta /= divi;
if (c_delta > cpu_tick_frequency) {
if (0 && bootverbose)
printf("cpu_tick increased to %ju Hz\n",
c_delta);
cpu_tick_frequency = c_delta;
}
}
}
c_last = c_this;
t_last = t_this;
}
void
set_cputicker(cpu_tick_f *func, uint64_t freq, unsigned var)
{
if (func == NULL) {
cpu_ticks = tc_cpu_ticks;
} else {
cpu_tick_frequency = freq;
cpu_tick_variable = var;
cpu_ticks = func;
}
}
uint64_t
cpu_tickrate(void)
{
if (cpu_ticks == tc_cpu_ticks)
return (tc_getfrequency());
return (cpu_tick_frequency);
}
/*
* We need to be slightly careful converting cputicks to microseconds.
* There is plenty of margin in 64 bits of microseconds (half a million
* years) and in 64 bits at 4 GHz (146 years), but if we do a multiply
* before divide conversion (to retain precision) we find that the
* margin shrinks to 1.5 hours (one millionth of 146y).
* With a three prong approach we never loose significant bits, no
* matter what the cputick rate and length of timeinterval is.
*/
uint64_t
cputick2usec(uint64_t tick)
{
if (tick > 18446744073709551LL) /* floor(2^64 / 1000) */
return (tick / (cpu_tickrate() / 1000000LL));
else if (tick > 18446744073709LL) /* floor(2^64 / 1000000) */
return ((tick * 1000LL) / (cpu_tickrate() / 1000LL));
else
return ((tick * 1000000LL) / cpu_tickrate());
}
cpu_tick_f *cpu_ticks = tc_cpu_ticks;
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