1 files changed, 447 insertions, 0 deletions

diff --git a/arch/ppc/kernel/time.c b/arch/ppc/kernel/time.c
new file mode 100644
index 000000000000..50724139402c
--- /dev/null
+++ b/arch/ppc/kernel/time.c
@@ -0,0 +1,447 @@
+/*
+ * 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;
+
+static long time_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 && (time_status & STA_UNSYNC) == 0 &&
+                     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 + time_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;
+
+        time_adjust = 0;                /* stop active adjtime() */
+        time_status |= STA_UNSYNC;
+        time_state = TIME_ERROR;        /* p. 24, (a) */
+        time_maxerror = NTP_PHASE_LIMIT;
+        time_esterror = NTP_PHASE_LIMIT;
+        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)
+                time_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 (time_offset) {
+                sys_tz.tz_minuteswest = -time_offset / 60;
+                sys_tz.tz_dsttime = 0;
+                xtime.tv_sec -= time_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;
+}