/*
* This version of gettimeofday has microsecond resolution.
*/
void do_gettimeofday(struct timeval *tv)
{
unsigned long flags;
unsigned long seq;
unsigned delta, lost_ticks, usec, sec;
do {
seq = read_seqbegin_irqsave(&xtime_lock, flags);
sec = xtime.tv_sec;
usec = (xtime.tv_nsec / 1000);
delta = tb_ticks_since(tb_last_stamp);
#ifdef CONFIG_SMP
/* As long as timebases are not in sync, gettimeofday can only
* have jiffy resolution on SMP.
*/
if (!smp_tb_synchronized)
delta = 0;
#endif /* CONFIG_SMP */
lost_ticks = jiffies - wall_jiffies;
} while (read_seqretry_irqrestore(&xtime_lock, seq, flags));
usec += mulhwu(tb_to_us, tb_ticks_per_jiffy * lost_ticks + delta);
while (usec >= 1000000) {
sec++;
usec -= 1000000;
}
tv->tv_sec = sec;
tv->tv_usec = usec;
}
/* This function is only called on the boot processor */
void __init time_init(void)
{
time_t sec, old_sec;
unsigned old_stamp, stamp, elapsed;
if (ppc_md.time_init != NULL)
timezone_offset = ppc_md.time_init();
if (__USE_RTC()) {
/* 601 processor: dec counts down by 128 every 128ns */
tb_ticks_per_jiffy = DECREMENTER_COUNT_601;
/* mulhwu_scale_factor(1000000000, 1000000) is 0x418937 */
tb_to_us = 0x418937;
} else {
ppc_md.calibrate_decr();
tb_to_ns_scale = mulhwu(tb_to_us, 1000 << 10);
}
/* Now that the decrementer is calibrated, it can be used in case the
* clock is stuck, but the fact that we have to handle the 601
* makes things more complex. Repeatedly read the RTC until the
* next second boundary to try to achieve some precision. If there
* is no RTC, we still need to set tb_last_stamp and
* last_jiffy_stamp(cpu 0) to the current stamp.
*/
stamp = get_native_tbl();
if (ppc_md.get_rtc_time) {
sec = ppc_md.get_rtc_time();
elapsed = 0;
do {
udelay(500); /* DS1553 need minimum 500 us to update */
old_stamp = stamp;
old_sec = sec;
stamp = get_native_tbl();
if (__USE_RTC() && stamp < old_stamp)
old_stamp -= 1000000000;
elapsed += stamp - old_stamp;
sec = ppc_md.get_rtc_time();
} while ( sec == old_sec && elapsed < 2*HZ*tb_ticks_per_jiffy);
if (sec==old_sec)
printk("Warning: real time clock seems stuck!\n");
xtime.tv_sec = sec;
xtime.tv_nsec = 0;
/* No update now, we just read the time from the RTC ! */
last_rtc_update = xtime.tv_sec;
}
last_jiffy_stamp(0) = tb_last_stamp = stamp;
/* Not exact, but the timer interrupt takes care of this */
set_dec(tb_ticks_per_jiffy);
/* If platform provided a timezone (pmac), we correct the time */
if (timezone_offset) {
sys_tz.tz_minuteswest = -timezone_offset / 60;
sys_tz.tz_dsttime = 0;
xtime.tv_sec -= timezone_offset;
}
set_normalized_timespec(&wall_to_monotonic,
-xtime.tv_sec, -xtime.tv_nsec);
}
int do_settimeofday(struct timespec *tv)
{
time_t wtm_sec, new_sec = tv->tv_sec;
long wtm_nsec, new_nsec = tv->tv_nsec;
unsigned long flags;
int tb_delta;
if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
return -EINVAL;
write_seqlock_irqsave(&xtime_lock, flags);
/* Updating the RTC is not the job of this code. If the time is
* stepped under NTP, the RTC will be update after STA_UNSYNC
* is cleared. Tool like clock/hwclock either copy the RTC
* to the system time, in which case there is no point in writing
* to the RTC again, or write to the RTC but then they don't call
* settimeofday to perform this operation. Note also that
* we don't touch the decrementer since:
* a) it would lose timer interrupt synchronization on SMP
* (if it is working one day)
* b) it could make one jiffy spuriously shorter or longer
* which would introduce another source of uncertainty potentially
* harmful to relatively short timers.
*/
/* This works perfectly on SMP only if the tb are in sync but
* guarantees an error < 1 jiffy even if they are off by eons,
* still reasonable when gettimeofday resolution is 1 jiffy.
*/
tb_delta = tb_ticks_since(last_jiffy_stamp(smp_processor_id()));
tb_delta += (jiffies - wall_jiffies) * tb_ticks_per_jiffy;
new_nsec -= 1000 * mulhwu(tb_to_us, tb_delta);
wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - new_sec);
wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - new_nsec);
set_normalized_timespec(&xtime, new_sec, new_nsec);
set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
/* In case of a large backwards jump in time with NTP, we want the
* clock to be updated as soon as the PLL is again in lock.
*/
last_rtc_update = new_sec - 658;
time_adjust = 0; /* stop active adjtime() */
time_status |= STA_UNSYNC;
time_maxerror = NTP_PHASE_LIMIT;
time_esterror = NTP_PHASE_LIMIT;
write_sequnlock_irqrestore(&xtime_lock, flags);
clock_was_set();
return 0;
}
/* Actually the choice of a timebase running at 1/4 the of the bus
* frequency giving resolution of a few tens of nanoseconds is quite nice.
* It makes this computation very precise (27-28 bits typically) which
* is optimistic considering the stability of most processor clock
* oscillators and the precision with which the timebase frequency
* is measured but does not harm.
*/
unsigned mulhwu_scale_factor(unsigned inscale, unsigned outscale) {
unsigned mlt=0, tmp, err;
/* No concern for performance, it's done once: use a stupid
* but safe and compact method to find the multiplier.
*/
for (tmp = 1U<<31; tmp != 0; tmp >>= 1) {
if (mulhwu(inscale, mlt|tmp) < outscale) mlt|=tmp;
}
/* We might still be off by 1 for the best approximation.
* A side effect of this is that if outscale is too large
* the returned value will be zero.
* Many corner cases have been checked and seem to work,
* some might have been forgotten in the test however.
*/
err = inscale*(mlt+1);
if (err <= inscale/2) mlt++;
return mlt;
}
