/*
* Common time routines among all ppc machines.
*
* Written by Cort Dougan (cort@cs.nmt.edu) to merge
* Paul Mackerras' version and mine for PReP and Pmac.
* MPC8xx/MBX changes by Dan Malek (dmalek@jlc.net).
*
* First round of bugfixes by Gabriel Paubert (paubert@iram.es)
* to make clock more stable (2.4.0-test5). The only thing
* that this code assumes is that the timebases have been synchronized
* by firmware on SMP and are never stopped (never do sleep
* on SMP then, nap and doze are OK).
*
* TODO (not necessarily in this file):
* - improve precision and reproducibility of timebase frequency
* measurement at boot time.
* - get rid of xtime_lock for gettimeofday (generic kernel problem
* to be implemented on all architectures for SMP scalability and
* eventually implementing gettimeofday without entering the kernel).
* - put all time/clock related variables in a single structure
* to minimize number of cache lines touched by gettimeofday()
* - for astronomical applications: add a new function to get
* non ambiguous timestamps even around leap seconds. This needs
* a new timestamp format and a good name.
*
*
* The following comment is partially obsolete (at least the long wait
* is no more a valid reason):
* Since the MPC8xx has a programmable interrupt timer, I decided to
* use that rather than the decrementer. Two reasons: 1.) the clock
* frequency is low, causing 2.) a long wait in the timer interrupt
* while ((d = get_dec()) == dval)
* loop. The MPC8xx can be driven from a variety of input clocks,
* so a number of assumptions have been made here because the kernel
* parameter HZ is a constant. We assume (correctly, today :-) that
* the MPC8xx on the MBX board is driven from a 32.768 kHz crystal.
* This is then divided by 4, providing a 8192 Hz clock into the PIT.
* Since it is not possible to get a nice 100 Hz clock out of this, without
* creating a software PLL, I have set HZ to 128. -- Dan
*
* 1997-09-10 Updated NTP code according to technical memorandum Jan '96
* "A Kernel Model for Precision Timekeeping" by Dave Mills
*/
#include <linux/config.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/param.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/timex.h>
#include <linux/kernel_stat.h>
#include <linux/mc146818rtc.h>
#include <linux/time.h>
#include <linux/init.h>
#include <linux/profile.h>
#include <asm/segment.h>
#include <asm/io.h>
#include <asm/nvram.h>
#include <asm/cache.h>
#include <asm/8xx_immap.h>
#include <asm/machdep.h>
#include <asm/time.h>
/* XXX false sharing with below? */
u64 jiffies_64 = INITIAL_JIFFIES;
EXPORT_SYMBOL(jiffies_64);
unsigned long disarm_decr[NR_CPUS];
extern struct timezone sys_tz;
/* keep track of when we need to update the rtc */
time_t last_rtc_update;
/* The decrementer counts down by 128 every 128ns on a 601. */
#define DECREMENTER_COUNT_601 (1000000000 / HZ)
unsigned tb_ticks_per_jiffy;
unsigned tb_to_us;
unsigned tb_last_stamp;
unsigned long tb_to_ns_scale;
extern unsigned long wall_jiffies;
/* used for timezone offset */
static long timezone_offset;
DEFINE_SPINLOCK(rtc_lock);
EXPORT_SYMBOL(rtc_lock);
/* Timer interrupt helper function */
static inline int tb_delta(unsigned *jiffy_stamp) {
int delta;
if (__USE_RTC()) {
delta = get_rtcl();
if (delta < *jiffy_stamp) *jiffy_stamp -= 1000000000;
delta -= *jiffy_stamp;
} else {
delta = get_tbl() - *jiffy_stamp;
}
return delta;
}
#ifdef CONFIG_SMP
unsigned long profile_pc(struct pt_regs *regs)
{
unsigned long pc = instruction_pointer(regs);
if (in_lock_functions(pc))
return regs->link;
return pc;
}
EXPORT_SYMBOL(profile_pc);
#endif
/*
* timer_interrupt - gets called when the decrementer overflows,
* with interrupts disabled.
* We set it up to overflow again in 1/HZ seconds.
*/
void timer_interrupt(struct pt_regs * regs)
{
int next_dec;
unsigned long cpu = smp_processor_id();
unsigned jiffy_stamp = last_jiffy_stamp(cpu);
extern void do_IRQ(struct pt_regs *);
if (atomic_read(&ppc_n_lost_interrupts) != 0)
do_IRQ(regs);
irq_enter();
while ((next_dec = tb_ticks_per_jiffy - tb_delta(&jiffy_stamp)) <= 0) {
jiffy_stamp += tb_ticks_per_jiffy;
profile_tick(CPU_PROFILING, regs);
update_process_times(user_mode(regs));
if (smp_processor_id())
continue;
/* We are in an interrupt, no need to save/restore flags */
write_seqlock(&xtime_lock);
tb_last_stamp = jiffy_stamp;
do_timer(regs);
/*
* update the rtc when needed, this should be performed on the
* right fraction of a second. Half or full second ?
* Full second works on mk48t59 clocks, others need testing.
* Note that this update is basically only used through
* the adjtimex system calls. Setting the HW clock in
* any other way is a /dev/rtc and userland business.
* This is still wrong by -0.5/+1.5 jiffies because of the
* timer interrupt resolution and possible delay, but here we
* hit a quantization limit which can only be solved by higher
* resolution timers and decoupling time management from timer
* interrupts. This is also wrong on the clocks
* which require being written at the half second boundary.
* We should have an rtc call that only sets the minutes and
* seconds like on Intel to avoid problems with non UTC clocks.
*/
if ( ppc_md.set_rtc_time && ntp_synced() &&
xtime.tv_sec - last_rtc_update >= 659 &&
abs((xtime.tv_nsec / 1000) - (1000000-1000000/HZ)) < 500000/HZ &&
jiffies - wall_jiffies == 1) {
if (ppc_md.set_rtc_time(xtime.tv_sec+1 + timezone_offset) == 0)
last_rtc_update = xtime.tv_sec+1;
else
/* Try again one minute later */
last_rtc_update += 60;
}
write_sequnlock(&xtime_lock);
}
if ( !disarm_decr[smp_processor_id()] )
set_dec(next_dec);
last_jiffy_stamp(cpu) = jiffy_stamp;
if (ppc_md.heartbeat && !ppc_md.heartbeat_count--)
ppc_md.heartbeat();
irq_exit();
}
/*
* 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;
}
EXPORT_SYMBOL(do_gettimeofday);
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;
ntp_clear();
write_sequnlock_irqrestore(&xtime_lock, flags);
clock_was_set();
return 0;
}
EXPORT_SYMBOL(do_settimeofday);
/* 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 {
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);
}
#define FEBRUARY 2
#define STARTOFTIME 1970
#define SECDAY 86400L
#define SECYR (SECDAY * 365)
/*
* Note: this is wrong for 2100, but our signed 32-bit time_t will
* have overflowed long before that, so who cares. -- paulus
*/
#define leapyear(year) ((year) % 4 == 0)
#define days_in_year(a) (leapyear(a) ? 366 : 365)
#define days_in_month(a) (month_days[(a) - 1])
static int month_days[12] = {
31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
};
void to_tm(int tim, struct rtc_time * tm)
{
register int i;
register long hms, day, gday;
gday = day = tim / SECDAY;
hms = tim % SECDAY;
/* Hours, minutes, seconds are easy */
tm->tm_hour = hms / 3600;
tm->tm_min = (hms % 3600) / 60;
tm->tm_sec = (hms % 3600) % 60;
/* Number of years in days */
for (i = STARTOFTIME; day >= days_in_year(i); i++)
day -= days_in_year(i);
tm->tm_year = i;
/* Number of months in days left */
if (leapyear(tm->tm_year))
days_in_month(FEBRUARY) = 29;
for (i = 1; day >= days_in_month(i); i++)
day -= days_in_month(i);
days_in_month(FEBRUARY) = 28;
tm->tm_mon = i;
/* Days are what is left over (+1) from all that. */
tm->tm_mday = day + 1;
/*
* Determine the day of week. Jan. 1, 1970 was a Thursday.
*/
tm->tm_wday = (gday + 4) % 7;
}
/* Auxiliary function to compute scaling factors */
/* 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;
}
unsigned long long sched_clock(void)
{
unsigned long lo, hi, hi2;
unsigned long long tb;
if (!__USE_RTC()) {
do {
hi = get_tbu();
lo = get_tbl();
hi2 = get_tbu();
} while (hi2 != hi);
tb = ((unsigned long long) hi << 32) | lo;
tb = (tb * tb_to_ns_scale) >> 10;
} else {
do {
hi = get_rtcu();
lo = get_rtcl();
hi2 = get_rtcu();
} while (hi2 != hi);
tb = ((unsigned long long) hi) * 1000000000 + lo;
}
return tb;
}
