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-rw-r--r--arch/ppc/kernel/time.c445
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diff --git a/arch/ppc/kernel/time.c b/arch/ppc/kernel/time.c
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-/*
- * 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/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/io.h>
-#include <asm/nvram.h>
-#include <asm/cache.h>
-#include <asm/8xx_immap.h>
-#include <asm/machdep.h>
-#include <asm/irq_regs.h>
-
-#include <asm/time.h>
-
-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;
-
-/* 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
-
-void wakeup_decrementer(void)
-{
- set_dec(tb_ticks_per_jiffy);
- /* No currently-supported powerbook has a 601,
- * so use get_tbl, not native
- */
- last_jiffy_stamp(0) = tb_last_stamp = get_tbl();
-}
-
-/*
- * 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)
-{
- struct pt_regs *old_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);
-
- old_regs = set_irq_regs(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);
- 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(1);
-
- /*
- * 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) {
- 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();
- set_irq_regs(old_regs);
-}
-
-/*
- * This version of gettimeofday has microsecond resolution.
- */
-void do_gettimeofday(struct timeval *tv)
-{
- unsigned long flags;
- unsigned long seq;
- unsigned delta, 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 */
- } while (read_seqretry_irqrestore(&xtime_lock, seq, flags));
-
- usec += mulhwu(tb_to_us, 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()));
-
- 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;
-}
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