From 3e736d509921e5071a688f5676c129762eda9909 Mon Sep 17 00:00:00 2001
From: John Stultz <johnstul@us.ibm.com>
Date: Wed, 20 Aug 2008 16:37:28 -0700
Subject: [PATCH] --- yaml --- r: 116337 b: refs/heads/master c:
 1aa5dfb751d275ae7117d3b73ac423b4a46f2a73 h: refs/heads/master i:   116335:
 cbcada497c7df7a777fb9273f1e84a833c5ac4f7 v: v3

---
 [refs]                            |  2 +-
 trunk/include/linux/clocksource.h | 11 +++++++----
 trunk/kernel/time/clocksource.c   |  3 +++
 trunk/kernel/time/jiffies.c       |  1 +
 4 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/[refs] b/[refs]
index ff8638fdac8b..8b647645f6a9 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: ee974e01e5ef2914036f08c8e41d1a3fa8bfc9d9
+refs/heads/master: 1aa5dfb751d275ae7117d3b73ac423b4a46f2a73
diff --git a/trunk/include/linux/clocksource.h b/trunk/include/linux/clocksource.h
index 55e434feec99..f0a7fb984413 100644
--- a/trunk/include/linux/clocksource.h
+++ b/trunk/include/linux/clocksource.h
@@ -45,7 +45,8 @@ struct clocksource;
  * @read:		returns a cycle value
  * @mask:		bitmask for two's complement
  *			subtraction of non 64 bit counters
- * @mult:		cycle to nanosecond multiplier
+ * @mult:		cycle to nanosecond multiplier (adjusted by NTP)
+ * @mult_orig:		cycle to nanosecond multiplier (unadjusted by NTP)
  * @shift:		cycle to nanosecond divisor (power of two)
  * @flags:		flags describing special properties
  * @vread:		vsyscall based read
@@ -63,6 +64,7 @@ struct clocksource {
 	cycle_t (*read)(void);
 	cycle_t mask;
 	u32 mult;
+	u32 mult_orig;
 	u32 shift;
 	unsigned long flags;
 	cycle_t (*vread)(void);
@@ -201,16 +203,17 @@ static inline void clocksource_calculate_interval(struct clocksource *c,
 {
 	u64 tmp;
 
-	/* XXX - All of this could use a whole lot of optimization */
+	/* Do the ns -> cycle conversion first, using original mult */
 	tmp = length_nsec;
 	tmp <<= c->shift;
-	tmp += c->mult/2;
-	do_div(tmp, c->mult);
+	tmp += c->mult_orig/2;
+	do_div(tmp, c->mult_orig);
 
 	c->cycle_interval = (cycle_t)tmp;
 	if (c->cycle_interval == 0)
 		c->cycle_interval = 1;
 
+	/* Go back from cycles -> shifted ns, this time use ntp adjused mult */
 	c->xtime_interval = (u64)c->cycle_interval * c->mult;
 }
 
diff --git a/trunk/kernel/time/clocksource.c b/trunk/kernel/time/clocksource.c
index 093d4acf993b..9ed2eec97526 100644
--- a/trunk/kernel/time/clocksource.c
+++ b/trunk/kernel/time/clocksource.c
@@ -325,6 +325,9 @@ int clocksource_register(struct clocksource *c)
 	unsigned long flags;
 	int ret;
 
+	/* save mult_orig on registration */
+	c->mult_orig = c->mult;
+
 	spin_lock_irqsave(&clocksource_lock, flags);
 	ret = clocksource_enqueue(c);
 	if (!ret)
diff --git a/trunk/kernel/time/jiffies.c b/trunk/kernel/time/jiffies.c
index 4c256fdb8875..1ca99557e929 100644
--- a/trunk/kernel/time/jiffies.c
+++ b/trunk/kernel/time/jiffies.c
@@ -61,6 +61,7 @@ struct clocksource clocksource_jiffies = {
 	.read		= jiffies_read,
 	.mask		= 0xffffffff, /*32bits*/
 	.mult		= NSEC_PER_JIFFY << JIFFIES_SHIFT, /* details above */
+	.mult_orig	= NSEC_PER_JIFFY << JIFFIES_SHIFT,
 	.shift		= JIFFIES_SHIFT,
 };