---

yaml
---
r: 30207
b: refs/heads/master
c: 5eb6d20
h: refs/heads/master
i:
  30205: 02ec523
  30203: a875267
  30199: 58a600b
  30191: dccc7e8
  30175: 21c38ba
  30143: ae9cc45
  30079: 57eca05
  29951: 2ed8f96
  29695: 149aa9b
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 260a42309b31cbc54eb4b6b85649e412bcad053f
+refs/heads/master: 5eb6d20533d14a432df714520939a6181e28f099

trunk/include/linux/clocksource.h

@@ -173,6 +173,103 @@ static inline void calculate_clocksource_interval(struct clocksource *c,
 	c->interval_snsecs = (u64)c->interval_cycles * c->mult;
 }
 
+
+/**
+ * error_aproximation - calculates an error adjustment for a given error
+ *
+ * @error:	Error value (unsigned)
+ * @unit:	Adjustment unit
+ *
+ * For a given error value, this function takes the adjustment unit
+ * and uses binary approximation to return a power of two adjustment value.
+ *
+ * This function is only for use by the the make_ntp_adj() function
+ * and you must hold a write on the xtime_lock when calling.
+ */
+static inline int error_aproximation(u64 error, u64 unit)
+{
+	static int saved_adj = 0;
+	u64 adjusted_unit = unit << saved_adj;
+
+	if (error > (adjusted_unit * 2)) {
+		/* large error, so increment the adjustment factor */
+		saved_adj++;
+	} else if (error > adjusted_unit) {
+		/* just right, don't touch it */
+	} else if (saved_adj) {
+		/* small error, so drop the adjustment factor */
+		saved_adj--;
+		return 0;
+	}
+
+	return saved_adj;
+}
+
+
+/**
+ * make_ntp_adj - Adjusts the specified clocksource for a given error
+ *
+ * @clock:		Pointer to clock to be adjusted
+ * @cycles_delta:	Current unacounted cycle delta
+ * @error:		Pointer to current error value
+ *
+ * Returns clock shifted nanosecond adjustment to be applied against
+ * the accumulated time value (ie: xtime).
+ *
+ * If the error value is large enough, this function calulates the
+ * (power of two) adjustment value, and adjusts the clock's mult and
+ * interval_snsecs values accordingly.
+ *
+ * However, since there may be some unaccumulated cycles, to avoid
+ * time inconsistencies we must adjust the accumulation value
+ * accordingly.
+ *
+ * This is not very intuitive, so the following proof should help:
+ * The basic timeofday algorithm:  base + cycle * mult
+ * Thus:
+ *    new_base + cycle * new_mult = old_base + cycle * old_mult
+ *    new_base = old_base + cycle * old_mult - cycle * new_mult
+ *    new_base = old_base + cycle * (old_mult - new_mult)
+ *    new_base - old_base = cycle * (old_mult - new_mult)
+ *    base_delta = cycle * (old_mult - new_mult)
+ *    base_delta = cycle * (mult_delta)
+ *
+ * Where mult_delta is the adjustment value made to mult
+ *
+ */
+static inline s64 make_ntp_adj(struct clocksource *clock,
+				cycles_t cycles_delta, s64* error)
+{
+	s64 ret = 0;
+	if (*error  > ((s64)clock->interval_cycles+1)/2) {
+		/* calculate adjustment value */
+		int adjustment = error_aproximation(*error,
+						clock->interval_cycles);
+		/* adjust clock */
+		clock->mult += 1 << adjustment;
+		clock->interval_snsecs += clock->interval_cycles << adjustment;
+
+		/* adjust the base and error for the adjustment */
+		ret =  -(cycles_delta << adjustment);
+		*error -= clock->interval_cycles << adjustment;
+		/* XXX adj error for cycle_delta offset? */
+	} else if ((-(*error))  > ((s64)clock->interval_cycles+1)/2) {
+		/* calculate adjustment value */
+		int adjustment = error_aproximation(-(*error),
+						clock->interval_cycles);
+		/* adjust clock */
+		clock->mult -= 1 << adjustment;
+		clock->interval_snsecs -= clock->interval_cycles << adjustment;
+
+		/* adjust the base and error for the adjustment */
+		ret =  cycles_delta << adjustment;
+		*error += clock->interval_cycles << adjustment;
+		/* XXX adj error for cycle_delta offset? */
+	}
+	return ret;
+}
+
+
 /* used to install a new clocksource */
 int register_clocksource(struct clocksource*);
 void reselect_clocksource(void);

trunk/kernel/timer.c

@@ -597,7 +597,6 @@ long time_tolerance = MAXFREQ;		/* frequency tolerance (ppm)	*/
 long time_precision = 1;		/* clock precision (us)		*/
 long time_maxerror = NTP_PHASE_LIMIT;	/* maximum error (us)		*/
 long time_esterror = NTP_PHASE_LIMIT;	/* estimated error (us)		*/
-static long time_phase;			/* phase offset (scaled us)	*/
 long time_freq = (((NSEC_PER_SEC + HZ/2) % HZ - HZ/2) << SHIFT_USEC) / NSEC_PER_USEC;
 					/* frequency offset (scaled ppm)*/
 static long time_adj;			/* tick adjust (scaled 1 / HZ)	*/
@@ -747,27 +746,14 @@ static long adjtime_adjustment(void)
 }
 
 /* in the NTP reference this is called "hardclock()" */
-static void update_wall_time_one_tick(void)
+static void update_ntp_one_tick(void)
 {
-	long time_adjust_step, delta_nsec;
+	long time_adjust_step;
 
 	time_adjust_step = adjtime_adjustment();
 	if (time_adjust_step)
 		/* Reduce by this step the amount of time left  */
 		time_adjust -= time_adjust_step;
-	delta_nsec = tick_nsec + time_adjust_step * 1000;
-	/*
-	 * Advance the phase, once it gets to one microsecond, then
-	 * advance the tick more.
-	 */
-	time_phase += time_adj;
-	if ((time_phase >= FINENSEC) || (time_phase <= -FINENSEC)) {
-		long ltemp = shift_right(time_phase, (SHIFT_SCALE - 10));
-		time_phase -= ltemp << (SHIFT_SCALE - 10);
-		delta_nsec += ltemp;
-	}
-	xtime.tv_nsec += delta_nsec;
-	time_interpolator_update(delta_nsec);
 
 	/* Changes by adjtime() do not take effect till next tick. */
 	if (time_next_adjust != 0) {
@@ -872,26 +858,49 @@ device_initcall(timekeeping_init_device);
  */
 static void update_wall_time(void)
 {
+	static s64 remainder_snsecs, error;
+	s64 snsecs_per_sec;
 	cycle_t now, offset;
 
+	snsecs_per_sec = (s64)NSEC_PER_SEC << clock->shift;
+	remainder_snsecs += (s64)xtime.tv_nsec << clock->shift;
+
 	now = read_clocksource(clock);
 	offset = (now - last_clock_cycle)&clock->mask;
 
 	/* normally this loop will run just once, however in the
 	 * case of lost or late ticks, it will accumulate correctly.
 	 */
 	while (offset > clock->interval_cycles) {
+		/* get the ntp interval in clock shifted nanoseconds */
+		s64 ntp_snsecs	= current_tick_length(clock->shift);
+
 		/* accumulate one interval */
+		remainder_snsecs += clock->interval_snsecs;
 		last_clock_cycle += clock->interval_cycles;
 		offset -= clock->interval_cycles;
 
-		update_wall_time_one_tick();
-		if (xtime.tv_nsec >= 1000000000) {
-			xtime.tv_nsec -= 1000000000;
+		/* interpolator bits */
+		time_interpolator_update(clock->interval_snsecs
+						>> clock->shift);
+		/* increment the NTP state machine */
+		update_ntp_one_tick();
+
+		/* accumulate error between NTP and clock interval */
+		error += (ntp_snsecs - (s64)clock->interval_snsecs);
+
+		/* correct the clock when NTP error is too big */
+		remainder_snsecs += make_ntp_adj(clock, offset, &error);
+
+		if (remainder_snsecs >= snsecs_per_sec) {
+			remainder_snsecs -= snsecs_per_sec;
 			xtime.tv_sec++;
 			second_overflow();
 		}
 	}
+	/* store full nanoseconds into xtime */
+	xtime.tv_nsec = remainder_snsecs >> clock->shift;
+	remainder_snsecs -= (s64)xtime.tv_nsec << clock->shift;
 }
 
 /*