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-rw-r--r--kernel/time/clocksource.c76
1 files changed, 76 insertions, 0 deletions
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index ca89e1593f08..c46c931a7fe7 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -31,6 +31,82 @@
#include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */
#include <linux/tick.h>
+void timecounter_init(struct timecounter *tc,
+ const struct cyclecounter *cc,
+ u64 start_tstamp)
+{
+ tc->cc = cc;
+ tc->cycle_last = cc->read(cc);
+ tc->nsec = start_tstamp;
+}
+EXPORT_SYMBOL(timecounter_init);
+
+/**
+ * timecounter_read_delta - get nanoseconds since last call of this function
+ * @tc: Pointer to time counter
+ *
+ * When the underlying cycle counter runs over, this will be handled
+ * correctly as long as it does not run over more than once between
+ * calls.
+ *
+ * The first call to this function for a new time counter initializes
+ * the time tracking and returns an undefined result.
+ */
+static u64 timecounter_read_delta(struct timecounter *tc)
+{
+ cycle_t cycle_now, cycle_delta;
+ u64 ns_offset;
+
+ /* read cycle counter: */
+ cycle_now = tc->cc->read(tc->cc);
+
+ /* calculate the delta since the last timecounter_read_delta(): */
+ cycle_delta = (cycle_now - tc->cycle_last) & tc->cc->mask;
+
+ /* convert to nanoseconds: */
+ ns_offset = cyclecounter_cyc2ns(tc->cc, cycle_delta);
+
+ /* update time stamp of timecounter_read_delta() call: */
+ tc->cycle_last = cycle_now;
+
+ return ns_offset;
+}
+
+u64 timecounter_read(struct timecounter *tc)
+{
+ u64 nsec;
+
+ /* increment time by nanoseconds since last call */
+ nsec = timecounter_read_delta(tc);
+ nsec += tc->nsec;
+ tc->nsec = nsec;
+
+ return nsec;
+}
+EXPORT_SYMBOL(timecounter_read);
+
+u64 timecounter_cyc2time(struct timecounter *tc,
+ cycle_t cycle_tstamp)
+{
+ u64 cycle_delta = (cycle_tstamp - tc->cycle_last) & tc->cc->mask;
+ u64 nsec;
+
+ /*
+ * Instead of always treating cycle_tstamp as more recent
+ * than tc->cycle_last, detect when it is too far in the
+ * future and treat it as old time stamp instead.
+ */
+ if (cycle_delta > tc->cc->mask / 2) {
+ cycle_delta = (tc->cycle_last - cycle_tstamp) & tc->cc->mask;
+ nsec = tc->nsec - cyclecounter_cyc2ns(tc->cc, cycle_delta);
+ } else {
+ nsec = cyclecounter_cyc2ns(tc->cc, cycle_delta) + tc->nsec;
+ }
+
+ return nsec;
+}
+EXPORT_SYMBOL(timecounter_cyc2time);
+
/* XXX - Would like a better way for initializing curr_clocksource */
extern struct clocksource clocksource_jiffies;