3 files changed, 36 insertions, 14 deletions

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index f4b9b80e1b95..4062f15bfbdd 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -68,6 +68,7 @@
 #include <linux/percpu.h>
 #include <linux/crash_dump.h>
 #include <linux/tboot.h>
+#include <linux/jiffies.h>
 
 #include <video/edid.h>
 
@@ -1034,6 +1035,8 @@ void __init setup_arch(char **cmdline_p)
         mcheck_init();
 
         arch_init_ideal_nops();
+
+        register_refined_jiffies(CLOCK_TICK_RATE);
 }
 
 #ifdef CONFIG_X86_32
diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h
index 4a7e3864e80d..388edb54bfb6 100644
--- a/include/linux/jiffies.h
+++ b/include/linux/jiffies.h
@@ -51,21 +51,10 @@
 #define SH_DIV(NOM,DEN,LSH) (   (((NOM) / (DEN)) << (LSH))              \
                              + ((((NOM) % (DEN)) << (LSH)) + (DEN) / 2) / (DEN))
 
-#ifdef CLOCK_TICK_RATE
-/* LATCH is used in the interval timer and ftape setup. */
-# define LATCH ((CLOCK_TICK_RATE + HZ/2) / HZ)  /* For divider */
-
-/*
- * HZ is the requested value. However the CLOCK_TICK_RATE may not allow
- * for exactly HZ. So SHIFTED_HZ is high res HZ ("<< 8" is for accuracy)
- */
-# define SHIFTED_HZ (SH_DIV(CLOCK_TICK_RATE, LATCH, 8))
-#else
-# define SHIFTED_HZ (HZ << 8)
-#endif
+extern int register_refined_jiffies(long clock_tick_rate);
 
 /* TICK_NSEC is the time between ticks in nsec assuming SHIFTED_HZ */
-#define TICK_NSEC (SH_DIV(1000000UL * 1000, SHIFTED_HZ, 8))
+#define TICK_NSEC ((NSEC_PER_SEC+HZ/2)/HZ)
 
 /* TICK_USEC is the time between ticks in usec assuming fake USER_HZ */
 #define TICK_USEC ((1000000UL + USER_HZ/2) / USER_HZ)
diff --git a/kernel/time/jiffies.c b/kernel/time/jiffies.c
index 46da0537c10b..6629bf7b5285 100644
--- a/kernel/time/jiffies.c
+++ b/kernel/time/jiffies.c
@@ -37,7 +37,7 @@
  * requested HZ value. It is also not recommended
  * for "tick-less" systems.
  */
-#define NSEC_PER_JIFFY  ((u32)((((u64)NSEC_PER_SEC)<<8)/SHIFTED_HZ))
+#define NSEC_PER_JIFFY  ((NSEC_PER_SEC+HZ/2)/HZ)
 
 /* Since jiffies uses a simple NSEC_PER_JIFFY multiplier
  * conversion, the .shift value could be zero. However
@@ -95,3 +95,33 @@ struct clocksource * __init __weak clocksource_default_clock(void)
 {
         return &clocksource_jiffies;
 }
+
+struct clocksource refined_jiffies;
+
+int register_refined_jiffies(long cycles_per_second)
+{
+        u64 nsec_per_tick, shift_hz;
+        long cycles_per_tick;
+
+
+
+        refined_jiffies = clocksource_jiffies;
+        refined_jiffies.name = "refined-jiffies";
+        refined_jiffies.rating++;
+
+        /* Calc cycles per tick */
+        cycles_per_tick = (cycles_per_second + HZ/2)/HZ;
+        /* shift_hz stores hz<<8 for extra accuracy */
+        shift_hz = (u64)cycles_per_second << 8;
+        shift_hz += cycles_per_tick/2;
+        do_div(shift_hz, cycles_per_tick);
+        /* Calculate nsec_per_tick using shift_hz */
+        nsec_per_tick = (u64)NSEC_PER_SEC << 8;
+        nsec_per_tick += (u32)shift_hz/2;
+        do_div(nsec_per_tick, (u32)shift_hz);
+
+        refined_jiffies.mult = ((u32)nsec_per_tick) << JIFFIES_SHIFT;
+
+        clocksource_register(&refined_jiffies);
+        return 0;
+}