diff options
Diffstat (limited to 'kernel/time/jiffies.c')
| -rw-r--r-- | kernel/time/jiffies.c | 64 |
1 files changed, 61 insertions, 3 deletions
diff --git a/kernel/time/jiffies.c b/kernel/time/jiffies.c index 5404a845690..a6a5bf53e86 100644 --- a/kernel/time/jiffies.c +++ b/kernel/time/jiffies.c @@ -22,8 +22,11 @@ ************************************************************************/ #include <linux/clocksource.h> #include <linux/jiffies.h> +#include <linux/module.h> #include <linux/init.h> +#include "tick-internal.h" + /* The Jiffies based clocksource is the lowest common * denominator clock source which should function on * all systems. It has the same coarse resolution as @@ -31,10 +34,10 @@ * inaccuracies caused by missed or lost timer * interrupts and the inability for the timer * interrupt hardware to accuratly tick at the - * requested HZ value. It is also not reccomended + * requested HZ value. It is also not recommended * for "tick-less" systems. */ -#define NSEC_PER_JIFFY ((u32)((((u64)NSEC_PER_SEC)<<8)/ACTHZ)) +#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 @@ -48,14 +51,20 @@ * HZ shrinks, so values greater than 8 overflow 32bits when * HZ=100. */ +#if HZ < 34 +#define JIFFIES_SHIFT 6 +#elif HZ < 67 +#define JIFFIES_SHIFT 7 +#else #define JIFFIES_SHIFT 8 +#endif static cycle_t jiffies_read(struct clocksource *cs) { return (cycle_t) jiffies; } -struct clocksource clocksource_jiffies = { +static struct clocksource clocksource_jiffies = { .name = "jiffies", .rating = 1, /* lowest valid rating*/ .read = jiffies_read, @@ -64,6 +73,25 @@ struct clocksource clocksource_jiffies = { .shift = JIFFIES_SHIFT, }; +__cacheline_aligned_in_smp DEFINE_SEQLOCK(jiffies_lock); + +#if (BITS_PER_LONG < 64) +u64 get_jiffies_64(void) +{ + unsigned long seq; + u64 ret; + + do { + seq = read_seqbegin(&jiffies_lock); + ret = jiffies_64; + } while (read_seqretry(&jiffies_lock, seq)); + return ret; +} +EXPORT_SYMBOL(get_jiffies_64); +#endif + +EXPORT_SYMBOL(jiffies); + static int __init init_jiffies_clocksource(void) { return clocksource_register(&clocksource_jiffies); @@ -75,3 +103,33 @@ 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; +} |