Move timekeeping code to timekeeping.c

Move the timekeeping code out of kernel/timer.c and into
kernel/time/timekeeping.c.  I made no cleanups or other changes in transit.

[akpm@linux-foundation.org: build fix]
Signed-off-by: John Stultz <johnstul@us.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 476 insertions, 0 deletions

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
new file mode 100644
index 000000000000..f9217bf644f6
--- /dev/null
+++ b/kernel/time/timekeeping.c
@@ -0,0 +1,476 @@
+/*
+ *  linux/kernel/time/timekeeping.c
+ *
+ *  Kernel timekeeping code and accessor functions
+ *
+ *  This code was moved from linux/kernel/timer.c.
+ *  Please see that file for copyright and history logs.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/percpu.h>
+#include <linux/init.h>
+#include <linux/mm.h>
+#include <linux/sysdev.h>
+#include <linux/clocksource.h>
+#include <linux/jiffies.h>
+#include <linux/time.h>
+#include <linux/tick.h>
+
+
+/*
+ * This read-write spinlock protects us from races in SMP while
+ * playing with xtime and avenrun.
+ */
+__attribute__((weak)) __cacheline_aligned_in_smp DEFINE_SEQLOCK(xtime_lock);
+
+EXPORT_SYMBOL(xtime_lock);
+
+
+/*
+ * The current time
+ * wall_to_monotonic is what we need to add to xtime (or xtime corrected
+ * for sub jiffie times) to get to monotonic time.  Monotonic is pegged
+ * at zero at system boot time, so wall_to_monotonic will be negative,
+ * however, we will ALWAYS keep the tv_nsec part positive so we can use
+ * the usual normalization.
+ */
+struct timespec xtime __attribute__ ((aligned (16)));
+struct timespec wall_to_monotonic __attribute__ ((aligned (16)));
+
+EXPORT_SYMBOL(xtime);
+
+
+static struct clocksource *clock; /* pointer to current clocksource */
+
+
+#ifdef CONFIG_GENERIC_TIME
+/**
+ * __get_nsec_offset - Returns nanoseconds since last call to periodic_hook
+ *
+ * private function, must hold xtime_lock lock when being
+ * called. Returns the number of nanoseconds since the
+ * last call to update_wall_time() (adjusted by NTP scaling)
+ */
+static inline s64 __get_nsec_offset(void)
+{
+        cycle_t cycle_now, cycle_delta;
+        s64 ns_offset;
+
+        /* read clocksource: */
+        cycle_now = clocksource_read(clock);
+
+        /* calculate the delta since the last update_wall_time: */
+        cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
+
+        /* convert to nanoseconds: */
+        ns_offset = cyc2ns(clock, cycle_delta);
+
+        return ns_offset;
+}
+
+/**
+ * __get_realtime_clock_ts - Returns the time of day in a timespec
+ * @ts:         pointer to the timespec to be set
+ *
+ * Returns the time of day in a timespec. Used by
+ * do_gettimeofday() and get_realtime_clock_ts().
+ */
+static inline void __get_realtime_clock_ts(struct timespec *ts)
+{
+        unsigned long seq;
+        s64 nsecs;
+
+        do {
+                seq = read_seqbegin(&xtime_lock);
+
+                *ts = xtime;
+                nsecs = __get_nsec_offset();
+
+        } while (read_seqretry(&xtime_lock, seq));
+
+        timespec_add_ns(ts, nsecs);
+}
+
+/**
+ * getnstimeofday - Returns the time of day in a timespec
+ * @ts:         pointer to the timespec to be set
+ *
+ * Returns the time of day in a timespec.
+ */
+void getnstimeofday(struct timespec *ts)
+{
+        __get_realtime_clock_ts(ts);
+}
+
+EXPORT_SYMBOL(getnstimeofday);
+
+/**
+ * do_gettimeofday - Returns the time of day in a timeval
+ * @tv:         pointer to the timeval to be set
+ *
+ * NOTE: Users should be converted to using get_realtime_clock_ts()
+ */
+void do_gettimeofday(struct timeval *tv)
+{
+        struct timespec now;
+
+        __get_realtime_clock_ts(&now);
+        tv->tv_sec = now.tv_sec;
+        tv->tv_usec = now.tv_nsec/1000;
+}
+
+EXPORT_SYMBOL(do_gettimeofday);
+/**
+ * do_settimeofday - Sets the time of day
+ * @tv:         pointer to the timespec variable containing the new time
+ *
+ * Sets the time of day to the new time and update NTP and notify hrtimers
+ */
+int do_settimeofday(struct timespec *tv)
+{
+        unsigned long flags;
+        time_t wtm_sec, sec = tv->tv_sec;
+        long wtm_nsec, nsec = tv->tv_nsec;
+
+        if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
+                return -EINVAL;
+
+        write_seqlock_irqsave(&xtime_lock, flags);
+
+        nsec -= __get_nsec_offset();
+
+        wtm_sec  = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
+        wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);
+
+        set_normalized_timespec(&xtime, sec, nsec);
+        set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
+
+        clock->error = 0;
+        ntp_clear();
+
+        update_vsyscall(&xtime, clock);
+
+        write_sequnlock_irqrestore(&xtime_lock, flags);
+
+        /* signal hrtimers about time change */
+        clock_was_set();
+
+        return 0;
+}
+
+EXPORT_SYMBOL(do_settimeofday);
+
+/**
+ * change_clocksource - Swaps clocksources if a new one is available
+ *
+ * Accumulates current time interval and initializes new clocksource
+ */
+static void change_clocksource(void)
+{
+        struct clocksource *new;
+        cycle_t now;
+        u64 nsec;
+
+        new = clocksource_get_next();
+
+        if (clock == new)
+                return;
+
+        now = clocksource_read(new);
+        nsec =  __get_nsec_offset();
+        timespec_add_ns(&xtime, nsec);
+
+        clock = new;
+        clock->cycle_last = now;
+
+        clock->error = 0;
+        clock->xtime_nsec = 0;
+        clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
+
+        tick_clock_notify();
+
+        printk(KERN_INFO "Time: %s clocksource has been installed.\n",
+               clock->name);
+}
+#else
+static inline void change_clocksource(void) { }
+#endif
+
+/**
+ * timekeeping_is_continuous - check to see if timekeeping is free running
+ */
+int timekeeping_is_continuous(void)
+{
+        unsigned long seq;
+        int ret;
+
+        do {
+                seq = read_seqbegin(&xtime_lock);
+
+                ret = clock->flags & CLOCK_SOURCE_VALID_FOR_HRES;
+
+        } while (read_seqretry(&xtime_lock, seq));
+
+        return ret;
+}
+
+/**
+ * read_persistent_clock -  Return time in seconds from the persistent clock.
+ *
+ * Weak dummy function for arches that do not yet support it.
+ * Returns seconds from epoch using the battery backed persistent clock.
+ * Returns zero if unsupported.
+ *
+ *  XXX - Do be sure to remove it once all arches implement it.
+ */
+unsigned long __attribute__((weak)) read_persistent_clock(void)
+{
+        return 0;
+}
+
+/*
+ * timekeeping_init - Initializes the clocksource and common timekeeping values
+ */
+void __init timekeeping_init(void)
+{
+        unsigned long flags;
+        unsigned long sec = read_persistent_clock();
+
+        write_seqlock_irqsave(&xtime_lock, flags);
+
+        ntp_clear();
+
+        clock = clocksource_get_next();
+        clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
+        clock->cycle_last = clocksource_read(clock);
+
+        xtime.tv_sec = sec;
+        xtime.tv_nsec = 0;
+        set_normalized_timespec(&wall_to_monotonic,
+                -xtime.tv_sec, -xtime.tv_nsec);
+
+        write_sequnlock_irqrestore(&xtime_lock, flags);
+}
+
+/* flag for if timekeeping is suspended */
+static int timekeeping_suspended;
+/* time in seconds when suspend began */
+static unsigned long timekeeping_suspend_time;
+
+/**
+ * timekeeping_resume - Resumes the generic timekeeping subsystem.
+ * @dev:        unused
+ *
+ * This is for the generic clocksource timekeeping.
+ * xtime/wall_to_monotonic/jiffies/etc are
+ * still managed by arch specific suspend/resume code.
+ */
+static int timekeeping_resume(struct sys_device *dev)
+{
+        unsigned long flags;
+        unsigned long now = read_persistent_clock();
+
+        write_seqlock_irqsave(&xtime_lock, flags);
+
+        if (now && (now > timekeeping_suspend_time)) {
+                unsigned long sleep_length = now - timekeeping_suspend_time;
+
+                xtime.tv_sec += sleep_length;
+                wall_to_monotonic.tv_sec -= sleep_length;
+        }
+        /* re-base the last cycle value */
+        clock->cycle_last = clocksource_read(clock);
+        clock->error = 0;
+        timekeeping_suspended = 0;
+        write_sequnlock_irqrestore(&xtime_lock, flags);
+
+        touch_softlockup_watchdog();
+
+        clockevents_notify(CLOCK_EVT_NOTIFY_RESUME, NULL);
+
+        /* Resume hrtimers */
+        hres_timers_resume();
+
+        return 0;
+}
+
+static int timekeeping_suspend(struct sys_device *dev, pm_message_t state)
+{
+        unsigned long flags;
+
+        write_seqlock_irqsave(&xtime_lock, flags);
+        timekeeping_suspended = 1;
+        timekeeping_suspend_time = read_persistent_clock();
+        write_sequnlock_irqrestore(&xtime_lock, flags);
+
+        clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);
+
+        return 0;
+}
+
+/* sysfs resume/suspend bits for timekeeping */
+static struct sysdev_class timekeeping_sysclass = {
+        .resume         = timekeeping_resume,
+        .suspend        = timekeeping_suspend,
+        set_kset_name("timekeeping"),
+};
+
+static struct sys_device device_timer = {
+        .id             = 0,
+        .cls            = &timekeeping_sysclass,
+};
+
+static int __init timekeeping_init_device(void)
+{
+        int error = sysdev_class_register(&timekeeping_sysclass);
+        if (!error)
+                error = sysdev_register(&device_timer);
+        return error;
+}
+
+device_initcall(timekeeping_init_device);
+
+/*
+ * If the error is already larger, we look ahead even further
+ * to compensate for late or lost adjustments.
+ */
+static __always_inline int clocksource_bigadjust(s64 error, s64 *interval,
+                                                 s64 *offset)
+{
+        s64 tick_error, i;
+        u32 look_ahead, adj;
+        s32 error2, mult;
+
+        /*
+         * Use the current error value to determine how much to look ahead.
+         * The larger the error the slower we adjust for it to avoid problems
+         * with losing too many ticks, otherwise we would overadjust and
+         * produce an even larger error.  The smaller the adjustment the
+         * faster we try to adjust for it, as lost ticks can do less harm
+         * here.  This is tuned so that an error of about 1 msec is adusted
+         * within about 1 sec (or 2^20 nsec in 2^SHIFT_HZ ticks).
+         */
+        error2 = clock->error >> (TICK_LENGTH_SHIFT + 22 - 2 * SHIFT_HZ);
+        error2 = abs(error2);
+        for (look_ahead = 0; error2 > 0; look_ahead++)
+                error2 >>= 2;
+
+        /*
+         * Now calculate the error in (1 << look_ahead) ticks, but first
+         * remove the single look ahead already included in the error.
+         */
+        tick_error = current_tick_length() >>
+                (TICK_LENGTH_SHIFT - clock->shift + 1);
+        tick_error -= clock->xtime_interval >> 1;
+        error = ((error - tick_error) >> look_ahead) + tick_error;
+
+        /* Finally calculate the adjustment shift value.  */
+        i = *interval;
+        mult = 1;
+        if (error < 0) {
+                error = -error;
+                *interval = -*interval;
+                *offset = -*offset;
+                mult = -1;
+        }
+        for (adj = 0; error > i; adj++)
+                error >>= 1;
+
+        *interval <<= adj;
+        *offset <<= adj;
+        return mult << adj;
+}
+
+/*
+ * Adjust the multiplier to reduce the error value,
+ * this is optimized for the most common adjustments of -1,0,1,
+ * for other values we can do a bit more work.
+ */
+static void clocksource_adjust(struct clocksource *clock, s64 offset)
+{
+        s64 error, interval = clock->cycle_interval;
+        int adj;
+
+        error = clock->error >> (TICK_LENGTH_SHIFT - clock->shift - 1);
+        if (error > interval) {
+                error >>= 2;
+                if (likely(error <= interval))
+                        adj = 1;
+                else
+                        adj = clocksource_bigadjust(error, &interval, &offset);
+        } else if (error < -interval) {
+                error >>= 2;
+                if (likely(error >= -interval)) {
+                        adj = -1;
+                        interval = -interval;
+                        offset = -offset;
+                } else
+                        adj = clocksource_bigadjust(error, &interval, &offset);
+        } else
+                return;
+
+        clock->mult += adj;
+        clock->xtime_interval += interval;
+        clock->xtime_nsec -= offset;
+        clock->error -= (interval - offset) <<
+                        (TICK_LENGTH_SHIFT - clock->shift);
+}
+
+/**
+ * update_wall_time - Uses the current clocksource to increment the wall time
+ *
+ * Called from the timer interrupt, must hold a write on xtime_lock.
+ */
+void update_wall_time(void)
+{
+        cycle_t offset;
+
+        /* Make sure we're fully resumed: */
+        if (unlikely(timekeeping_suspended))
+                return;
+
+#ifdef CONFIG_GENERIC_TIME
+        offset = (clocksource_read(clock) - clock->cycle_last) & clock->mask;
+#else
+        offset = clock->cycle_interval;
+#endif
+        clock->xtime_nsec += (s64)xtime.tv_nsec << clock->shift;
+
+        /* normally this loop will run just once, however in the
+         * case of lost or late ticks, it will accumulate correctly.
+         */
+        while (offset >= clock->cycle_interval) {
+                /* accumulate one interval */
+                clock->xtime_nsec += clock->xtime_interval;
+                clock->cycle_last += clock->cycle_interval;
+                offset -= clock->cycle_interval;
+
+                if (clock->xtime_nsec >= (u64)NSEC_PER_SEC << clock->shift) {
+                        clock->xtime_nsec -= (u64)NSEC_PER_SEC << clock->shift;
+                        xtime.tv_sec++;
+                        second_overflow();
+                }
+
+                /* interpolator bits */
+                time_interpolator_update(clock->xtime_interval
+                                                >> clock->shift);
+
+                /* accumulate error between NTP and clock interval */
+                clock->error += current_tick_length();
+                clock->error -= clock->xtime_interval << (TICK_LENGTH_SHIFT - clock->shift);
+        }
+
+        /* correct the clock when NTP error is too big */
+        clocksource_adjust(clock, offset);
+
+        /* store full nanoseconds into xtime */
+        xtime.tv_nsec = (s64)clock->xtime_nsec >> clock->shift;
+        clock->xtime_nsec -= (s64)xtime.tv_nsec << clock->shift;
+
+        /* check to see if there is a new clocksource to use */
+        change_clocksource();
+        update_vsyscall(&xtime, clock);
+}