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23#include <linux/clocksource.h>
24#include <linux/jiffies.h>
25#include <linux/module.h>
26#include <linux/init.h>
27
28#include "timekeeping.h"
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38
39
40#define NSEC_PER_JIFFY ((NSEC_PER_SEC+HZ/2)/HZ)
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53
54#if HZ < 34
55#define JIFFIES_SHIFT 6
56#elif HZ < 67
57#define JIFFIES_SHIFT 7
58#else
59#define JIFFIES_SHIFT 8
60#endif
61
62static cycle_t jiffies_read(struct clocksource *cs)
63{
64 return (cycle_t) jiffies;
65}
66
67static struct clocksource clocksource_jiffies = {
68 .name = "jiffies",
69 .rating = 1,
70 .read = jiffies_read,
71 .mask = 0xffffffff,
72 .mult = NSEC_PER_JIFFY << JIFFIES_SHIFT,
73 .shift = JIFFIES_SHIFT,
74 .max_cycles = 10,
75};
76
77__cacheline_aligned_in_smp DEFINE_SEQLOCK(jiffies_lock);
78
79#if (BITS_PER_LONG < 64)
80u64 get_jiffies_64(void)
81{
82 unsigned long seq;
83 u64 ret;
84
85 do {
86 seq = read_seqbegin(&jiffies_lock);
87 ret = jiffies_64;
88 } while (read_seqretry(&jiffies_lock, seq));
89 return ret;
90}
91EXPORT_SYMBOL(get_jiffies_64);
92#endif
93
94EXPORT_SYMBOL(jiffies);
95
96static int __init init_jiffies_clocksource(void)
97{
98 return __clocksource_register(&clocksource_jiffies);
99}
100
101core_initcall(init_jiffies_clocksource);
102
103struct clocksource * __init __weak clocksource_default_clock(void)
104{
105 return &clocksource_jiffies;
106}
107
108struct clocksource refined_jiffies;
109
110int register_refined_jiffies(long cycles_per_second)
111{
112 u64 nsec_per_tick, shift_hz;
113 long cycles_per_tick;
114
115
116
117 refined_jiffies = clocksource_jiffies;
118 refined_jiffies.name = "refined-jiffies";
119 refined_jiffies.rating++;
120
121
122 cycles_per_tick = (cycles_per_second + HZ/2)/HZ;
123
124 shift_hz = (u64)cycles_per_second << 8;
125 shift_hz += cycles_per_tick/2;
126 do_div(shift_hz, cycles_per_tick);
127
128 nsec_per_tick = (u64)NSEC_PER_SEC << 8;
129 nsec_per_tick += (u32)shift_hz/2;
130 do_div(nsec_per_tick, (u32)shift_hz);
131
132 refined_jiffies.mult = ((u32)nsec_per_tick) << JIFFIES_SHIFT;
133
134 __clocksource_register(&refined_jiffies);
135 return 0;
136}
137