Message-Id: <20070426202702.23343.10036.sendpatchset@rambler.zko.hp.com>
Date:	Thu, 26 Apr 2007 16:27:02 -0400
From:	Peter Keilty <peter.keilty@...com>
To:	linux-ia64@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, John Stultz <johnstul@...ibm.com>,
	Peter Keilty <peter.keilty@...com>,
	Eric Whitney <eric.whitney@...com>
Subject: [PATCH 2/3] ia64: remove interpolater code

From: Peter Keilty <peter.keilty@...com>

Remove time_interpolator code.

Signed-off-by: Peter Keilty <peter.keilty@...com>
Signed-off-by: John Stultz <johnstul@...ibm.com>

---

 include/linux/timex.h |   60 ---------------
 kernel/time.c         |    1 
 kernel/timer.c        |  193 --------------------------------------------------
 3 files changed, 254 deletions(-)

linux-2.6.21-rc1_timeofday-remove-interp_C7.patch
============================================
diff --git a/include/linux/timex.h b/include/linux/timex.h
index da929db..37ac3ff 100644
--- a/include/linux/timex.h
+++ b/include/linux/timex.h
@@ -224,66 +224,6 @@ #define shift_right(x, s) ({	\
 	__x < 0 ? -(-__x >> __s) : __x >> __s;	\
 })
 
-
-#ifdef CONFIG_TIME_INTERPOLATION
-
-#define TIME_SOURCE_CPU 0
-#define TIME_SOURCE_MMIO64 1
-#define TIME_SOURCE_MMIO32 2
-#define TIME_SOURCE_FUNCTION 3
-
-/* For proper operations time_interpolator clocks must run slightly slower
- * than the standard clock since the interpolator may only correct by having
- * time jump forward during a tick. A slower clock is usually a side effect
- * of the integer divide of the nanoseconds in a second by the frequency.
- * The accuracy of the division can be increased by specifying a shift.
- * However, this may cause the clock not to be slow enough.
- * The interpolator will self-tune the clock by slowing down if no
- * resets occur or speeding up if the time jumps per analysis cycle
- * become too high.
- *
- * Setting jitter compensates for a fluctuating timesource by comparing
- * to the last value read from the timesource to insure that an earlier value
- * is not returned by a later call. The price to pay
- * for the compensation is that the timer routines are not as scalable anymore.
- */
-
-struct time_interpolator {
-	u16 source;			/* time source flags */
-	u8 shift;			/* increases accuracy of multiply by shifting. */
-				/* Note that bits may be lost if shift is set too high */
-	u8 jitter;			/* if set compensate for fluctuations */
-	u32 nsec_per_cyc;		/* set by register_time_interpolator() */
-	void *addr;			/* address of counter or function */
-	cycles_t mask;			/* mask the valid bits of the counter */
-	unsigned long offset;		/* nsec offset at last update of interpolator */
-	u64 last_counter;		/* counter value in units of the counter at last update */
-	cycles_t last_cycle;		/* Last timer value if TIME_SOURCE_JITTER is set */
-	u64 frequency;			/* frequency in counts/second */
-	long drift;			/* drift in parts-per-million (or -1) */
-	unsigned long skips;		/* skips forward */
-	unsigned long ns_skipped;	/* nanoseconds skipped */
-	struct time_interpolator *next;
-};
-
-extern void register_time_interpolator(struct time_interpolator *);
-extern void unregister_time_interpolator(struct time_interpolator *);
-extern void time_interpolator_reset(void);
-extern unsigned long time_interpolator_get_offset(void);
-extern void time_interpolator_update(long delta_nsec);
-
-#else /* !CONFIG_TIME_INTERPOLATION */
-
-static inline void time_interpolator_reset(void)
-{
-}
-
-static inline void time_interpolator_update(long delta_nsec)
-{
-}
-
-#endif /* !CONFIG_TIME_INTERPOLATION */
-
 #define TICK_LENGTH_SHIFT	32
 
 #ifdef CONFIG_NO_HZ
diff --git a/kernel/time.c b/kernel/time.c
index c6c80ea..53b73fd 100644
--- a/kernel/time.c
+++ b/kernel/time.c
@@ -134,7 +134,6 @@ static inline void warp_clock(void)
 	write_seqlock_irq(&xtime_lock);
 	wall_to_monotonic.tv_sec -= sys_tz.tz_minuteswest * 60;
 	xtime.tv_sec += sys_tz.tz_minuteswest * 60;
-	time_interpolator_reset();
 	write_sequnlock_irq(&xtime_lock);
 	clock_was_set();
 }
diff --git a/kernel/timer.c b/kernel/timer.c
index cb1b86a..f812456 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -751,7 +751,6 @@ struct timespec wall_to_monotonic __attr
 
 EXPORT_SYMBOL(xtime);
 
-
 /* XXX - all of this timekeeping code should be later moved to time.c */
 #include <linux/clocksource.h>
 static struct clocksource *clock; /* pointer to current clocksource */
@@ -1156,10 +1155,6 @@ #endif
 			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);
@@ -1708,194 +1703,6 @@ void __init init_timers(void)
 	open_softirq(TIMER_SOFTIRQ, run_timer_softirq, NULL);
 }
 
-#ifdef CONFIG_TIME_INTERPOLATION
-
-struct time_interpolator *time_interpolator __read_mostly;
-static struct time_interpolator *time_interpolator_list __read_mostly;
-static DEFINE_SPINLOCK(time_interpolator_lock);
-
-static inline cycles_t time_interpolator_get_cycles(unsigned int src)
-{
-	unsigned long (*x)(void);
-
-	switch (src)
-	{
-		case TIME_SOURCE_FUNCTION:
-			x = time_interpolator->addr;
-			return x();
-
-		case TIME_SOURCE_MMIO64	:
-			return readq_relaxed((void __iomem *)time_interpolator->addr);
-
-		case TIME_SOURCE_MMIO32	:
-			return readl_relaxed((void __iomem *)time_interpolator->addr);
-
-		default: return get_cycles();
-	}
-}
-
-static inline u64 time_interpolator_get_counter(int writelock)
-{
-	unsigned int src = time_interpolator->source;
-
-	if (time_interpolator->jitter)
-	{
-		cycles_t lcycle;
-		cycles_t now;
-
-		do {
-			lcycle = time_interpolator->last_cycle;
-			now = time_interpolator_get_cycles(src);
-			if (lcycle && time_after(lcycle, now))
-				return lcycle;
-
-			/* When holding the xtime write lock, there's no need
-			 * to add the overhead of the cmpxchg.  Readers are
-			 * force to retry until the write lock is released.
-			 */
-			if (writelock) {
-				time_interpolator->last_cycle = now;
-				return now;
-			}
-			/* Keep track of the last timer value returned. The use of cmpxchg here
-			 * will cause contention in an SMP environment.
-			 */
-		} while (unlikely(cmpxchg(&time_interpolator->last_cycle, lcycle, now) != lcycle));
-		return now;
-	}
-	else
-		return time_interpolator_get_cycles(src);
-}
-
-void time_interpolator_reset(void)
-{
-	time_interpolator->offset = 0;
-	time_interpolator->last_counter = time_interpolator_get_counter(1);
-}
-
-#define GET_TI_NSECS(count,i) (((((count) - i->last_counter) & (i)->mask) * (i)->nsec_per_cyc) >> (i)->shift)
-
-unsigned long time_interpolator_get_offset(void)
-{
-	/* If we do not have a time interpolator set up then just return zero */
-	if (!time_interpolator)
-		return 0;
-
-	return time_interpolator->offset +
-		GET_TI_NSECS(time_interpolator_get_counter(0), time_interpolator);
-}
-
-#define INTERPOLATOR_ADJUST 65536
-#define INTERPOLATOR_MAX_SKIP 10*INTERPOLATOR_ADJUST
-
-void time_interpolator_update(long delta_nsec)
-{
-	u64 counter;
-	unsigned long offset;
-
-	/* If there is no time interpolator set up then do nothing */
-	if (!time_interpolator)
-		return;
-
-	/*
-	 * The interpolator compensates for late ticks by accumulating the late
-	 * time in time_interpolator->offset. A tick earlier than expected will
-	 * lead to a reset of the offset and a corresponding jump of the clock
-	 * forward. Again this only works if the interpolator clock is running
-	 * slightly slower than the regular clock and the tuning logic insures
-	 * that.
-	 */
-
-	counter = time_interpolator_get_counter(1);
-	offset = time_interpolator->offset +
-			GET_TI_NSECS(counter, time_interpolator);
-
-	if (delta_nsec < 0 || (unsigned long) delta_nsec < offset)
-		time_interpolator->offset = offset - delta_nsec;
-	else {
-		time_interpolator->skips++;
-		time_interpolator->ns_skipped += delta_nsec - offset;
-		time_interpolator->offset = 0;
-	}
-	time_interpolator->last_counter = counter;
-
-	/* Tuning logic for time interpolator invoked every minute or so.
-	 * Decrease interpolator clock speed if no skips occurred and an offset is carried.
-	 * Increase interpolator clock speed if we skip too much time.
-	 */
-	if (jiffies % INTERPOLATOR_ADJUST == 0)
-	{
-		if (time_interpolator->skips == 0 && time_interpolator->offset > tick_nsec)
-			time_interpolator->nsec_per_cyc--;
-		if (time_interpolator->ns_skipped > INTERPOLATOR_MAX_SKIP && time_interpolator->offset == 0)
-			time_interpolator->nsec_per_cyc++;
-		time_interpolator->skips = 0;
-		time_interpolator->ns_skipped = 0;
-	}
-}
-
-static inline int
-is_better_time_interpolator(struct time_interpolator *new)
-{
-	if (!time_interpolator)
-		return 1;
-	return new->frequency > 2*time_interpolator->frequency ||
-	    (unsigned long)new->drift < (unsigned long)time_interpolator->drift;
-}
-
-void
-register_time_interpolator(struct time_interpolator *ti)
-{
-	unsigned long flags;
-
-	/* Sanity check */
-	BUG_ON(ti->frequency == 0 || ti->mask == 0);
-
-	ti->nsec_per_cyc = ((u64)NSEC_PER_SEC << ti->shift) / ti->frequency;
-	spin_lock(&time_interpolator_lock);
-	write_seqlock_irqsave(&xtime_lock, flags);
-	if (is_better_time_interpolator(ti)) {
-		time_interpolator = ti;
-		time_interpolator_reset();
-	}
-	write_sequnlock_irqrestore(&xtime_lock, flags);
-
-	ti->next = time_interpolator_list;
-	time_interpolator_list = ti;
-	spin_unlock(&time_interpolator_lock);
-}
-
-void
-unregister_time_interpolator(struct time_interpolator *ti)
-{
-	struct time_interpolator *curr, **prev;
-	unsigned long flags;
-
-	spin_lock(&time_interpolator_lock);
-	prev = &time_interpolator_list;
-	for (curr = *prev; curr; curr = curr->next) {
-		if (curr == ti) {
-			*prev = curr->next;
-			break;
-		}
-		prev = &curr->next;
-	}
-
-	write_seqlock_irqsave(&xtime_lock, flags);
-	if (ti == time_interpolator) {
-		/* we lost the best time-interpolator: */
-		time_interpolator = NULL;
-		/* find the next-best interpolator */
-		for (curr = time_interpolator_list; curr; curr = curr->next)
-			if (is_better_time_interpolator(curr))
-				time_interpolator = curr;
-		time_interpolator_reset();
-	}
-	write_sequnlock_irqrestore(&xtime_lock, flags);
-	spin_unlock(&time_interpolator_lock);
-}
-#endif /* CONFIG_TIME_INTERPOLATION */
-
 /**
  * msleep - sleep safely even with waitqueue interruptions
  * @msecs: Time in milliseconds to sleep for
-
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