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authorJordan Hargrave <jordan_hargrave@dell.com>2006-04-07 19:50:18 +0200
committerLinus Torvalds <torvalds@g5.osdl.org>2006-04-09 11:53:53 -0700
commitb20367a6c2a0cd937cb1f0a8cf848f1402fef99c (patch)
tree8624096baed40f8f89e757b2d170a7b4d1844575
parent49c93e84d8b2d602a07c302c7e3cd4fa09095fbb (diff)
downloadop-kernel-dev-b20367a6c2a0cd937cb1f0a8cf848f1402fef99c.zip
op-kernel-dev-b20367a6c2a0cd937cb1f0a8cf848f1402fef99c.tar.gz
[PATCH] x86_64: Fix drift with HPET timer enabled
If the HPET timer is enabled, the clock can drift by ~3 seconds a day. This is due to the HPET timer not being initialized with the correct setting (still using PIT count). If HZ changes, this drift can become even more pronounced. HPET patch initializes tick_nsec with correct tick_nsec settings for HPET timer. Vojtech comments: "It's not entirely correct (it assumes the HPET ticks totally exactly), but it's significantly better than assuming the PIT error there." Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--arch/x86_64/kernel/time.c2
-rw-r--r--include/asm-i386/hpet.h1
-rw-r--r--include/asm-x86_64/hpet.h2
-rw-r--r--include/linux/jiffies.h6
-rw-r--r--kernel/timer.c2
5 files changed, 12 insertions, 1 deletions
diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
index 2eeaa95..7392570 100644
--- a/arch/x86_64/kernel/time.c
+++ b/arch/x86_64/kernel/time.c
@@ -917,6 +917,8 @@ void __init time_init(void)
vxtime.hpet_address = 0;
if (hpet_use_timer) {
+ /* set tick_nsec to use the proper rate for HPET */
+ tick_nsec = TICK_NSEC_HPET;
cpu_khz = hpet_calibrate_tsc();
timename = "HPET";
#ifdef CONFIG_X86_PM_TIMER
diff --git a/include/asm-i386/hpet.h b/include/asm-i386/hpet.h
index 16ef9f9..7f1a8a6 100644
--- a/include/asm-i386/hpet.h
+++ b/include/asm-i386/hpet.h
@@ -89,6 +89,7 @@
* then 32 bit HPET counter wrapsaround in less than 0.5 sec.
*/
#define HPET_MIN_PERIOD (100000UL)
+#define HPET_TICK_RATE (HZ * 100000UL)
extern unsigned long hpet_tick; /* hpet clks count per tick */
extern unsigned long hpet_address; /* hpet memory map physical address */
diff --git a/include/asm-x86_64/hpet.h b/include/asm-x86_64/hpet.h
index 08b75c1..18ff7ee 100644
--- a/include/asm-x86_64/hpet.h
+++ b/include/asm-x86_64/hpet.h
@@ -51,6 +51,8 @@
#define HPET_TN_ROUTE_SHIFT 9
+#define HPET_TICK_RATE (HZ * 100000UL)
+
extern int is_hpet_enabled(void);
extern int hpet_rtc_timer_init(void);
extern int oem_force_hpet_timer(void);
diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h
index 99905e1..0433769 100644
--- a/include/linux/jiffies.h
+++ b/include/linux/jiffies.h
@@ -36,6 +36,8 @@
/* LATCH is used in the interval timer and ftape setup. */
#define LATCH ((CLOCK_TICK_RATE + HZ/2) / HZ) /* For divider */
+#define LATCH_HPET ((HPET_TICK_RATE + HZ/2) / HZ)
+
/* Suppose we want to devide two numbers NOM and DEN: NOM/DEN, the we can
* improve accuracy by shifting LSH bits, hence calculating:
* (NOM << LSH) / DEN
@@ -51,9 +53,13 @@
/* HZ is the requested value. ACTHZ is actual HZ ("<< 8" is for accuracy) */
#define ACTHZ (SH_DIV (CLOCK_TICK_RATE, LATCH, 8))
+#define ACTHZ_HPET (SH_DIV (HPET_TICK_RATE, LATCH_HPET, 8))
+
/* TICK_NSEC is the time between ticks in nsec assuming real ACTHZ */
#define TICK_NSEC (SH_DIV (1000000UL * 1000, ACTHZ, 8))
+#define TICK_NSEC_HPET (SH_DIV(1000000UL * 1000, ACTHZ_HPET, 8))
+
/* 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/timer.c b/kernel/timer.c
index c3a874f..471ab87 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -1455,7 +1455,7 @@ static void time_interpolator_update(long delta_nsec)
*/
if (jiffies % INTERPOLATOR_ADJUST == 0)
{
- if (time_interpolator->skips == 0 && time_interpolator->offset > TICK_NSEC)
+ 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++;
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