[PATCH 5/10] Time: Introduce arch generic time accessors

john stultz
2006-03-23T03:06:30Z

Introduces clocksource switching code and the arch generic time
accessor functions that use the clocksource infrastructure.

Signed-off-by: John Stultz <johnstul@us.ibm.com>

include/linux/time.h | 15 ++++
kernel/time.c | 2
kernel/timer.c | 170 +++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 187 insertions(+)

linux-2.6.16_timeofday-core4_C1.patch
============================================
diff --git a/include/linux/time.h b/include/linux/time.h
index 84cfa7b..fc06884 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -107,6 +107,7 @@ extern int do_getitimer(int which, struc
extern void getnstimeofday(struct timespec *tv);

extern struct timespec timespec_trunc(struct timespec t, unsigned gran);
+extern int timekeeping_is_continuous(void);

/**
* timespec_to_ns - Convert timespec to nanoseconds
@@ -149,6 +150,20 @@ extern struct timespec ns_to_timespec(co
*/
extern struct timeval ns_to_timeval(const nsec_t nsec);

+/**
+ * timespec_add_ns - Adds nanoseconds to a timespec
+ * @a: pointer to timespec to be incremented
+ * @ns: unsigned nanoseconds value to be added
+ */
+static inline void timespec_add_ns(struct timespec *a, u64 ns)
+{
+ ns += a->tv_nsec;
+ while(unlikely(ns >= NSEC_PER_SEC)) {
+ ns -= NSEC_PER_SEC;
+ a->tv_sec++;
+ }
+ a->tv_nsec = ns;
+}
#endif /* __KERNEL__ */

#define NFDBITS __NFDBITS
diff --git a/kernel/time.c b/kernel/time.c
index 8045391..526fbdb 100644
--- a/kernel/time.c
+++ b/kernel/time.c
@@ -550,6 +550,7 @@ EXPORT_SYMBOL(do_gettimeofday);

#else
+#ifndef CONFIG_GENERIC_TIME
/*
* Simulate gettimeofday using do_gettimeofday which only allows a timeval
* and therefore only yields usec accuracy
@@ -564,6 +565,7 @@ void getnstimeofday(struct timespec *tv)
}
EXPORT_SYMBOL_GPL(getnstimeofday);
#endif
+#endif

/* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
* Assumes input in normal date format, i.e. 1980-12-31 23:59:59
diff --git a/kernel/timer.c b/kernel/timer.c
index 339d52f..0c1e184 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -806,6 +806,169 @@ u64 current_tick_length(long shift)
#include <linux/clocksource.h>
static struct clocksource *clock; /* pointer to current clocksource */
static cycle_t last_clock_cycle; /* cycle value at last update_wall_time */
+
+#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 = read_clocksource(clock);
+
+ /* calculate the delta since the last update_wall_time: */
+ cycle_delta = (cycle_now - last_clock_cycle) & 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);
+}
+
+/**
+ * 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.
+ */
+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);
+
+ ntp_clear();
+
+ 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 int change_clocksource(void)
+{
+ struct clocksource *new;
+ cycle_t now;
+ u64 nsec;
+ new = get_next_clocksource();
+ if (clock != new) {
+ now = read_clocksource(new);
+ nsec = __get_nsec_offset();
+ timespec_add_ns(&xtime, nsec);
+
+ clock = new;
+ last_clock_cycle = now;
+ printk(KERN_INFO "Time: %s clocksource has been installed.\n",
+ clock->name);
+ return 1;
+ } else if (clock->update_callback) {
+ return clock->update_callback();
+ }
+ return 0;
+}
+#else
+#define change_clocksource() (0)
+#endif
+
+/**
+ * timeofday_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->is_continuous;
+
+ } while (read_seqretry(&xtime_lock, seq));
+
+ return ret;
+}
+
/*
* timekeeping_init - Initializes the clocksource and common timekeeping values
*/
@@ -912,6 +1075,13 @@ static void update_wall_time(void)
/* store full nanoseconds into xtime */
xtime.tv_nsec = remainder_snsecs >> clock->shift;
remainder_snsecs -= (s64)xtime.tv_nsec << clock->shift;
+
+ /* check to see if there is a new clocksource to use */
+ if (change_clocksource()) {
+ error = 0;
+ remainder_snsecs = 0;
+ calculate_clocksource_interval(clock, tick_nsec);
+ }
}

/*