diff options
| -rw-r--r-- | arch/x86/kernel/setup.c | 3 | ||||
| -rw-r--r-- | include/linux/jiffies.h | 15 | ||||
| -rw-r--r-- | kernel/time/jiffies.c | 32 |
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; +} |