1
2
3
4
5
6
7#include <linux/clocksource.h>
8#include <linux/jiffies.h>
9#include <linux/module.h>
10#include <linux/init.h>
11
12#include "timekeeping.h"
13#include "tick-internal.h"
14
15
16static u64 jiffies_read(struct clocksource *cs)
17{
18 return (u64) jiffies;
19}
20
21
22
23
24
25
26
27
28
29
30
31
32static struct clocksource clocksource_jiffies = {
33 .name = "jiffies",
34 .rating = 1,
35 .uncertainty_margin = 32 * NSEC_PER_MSEC,
36 .read = jiffies_read,
37 .mask = CLOCKSOURCE_MASK(32),
38 .mult = TICK_NSEC << JIFFIES_SHIFT,
39 .shift = JIFFIES_SHIFT,
40 .max_cycles = 10,
41};
42
43__cacheline_aligned_in_smp DEFINE_RAW_SPINLOCK(jiffies_lock);
44__cacheline_aligned_in_smp seqcount_raw_spinlock_t jiffies_seq =
45 SEQCNT_RAW_SPINLOCK_ZERO(jiffies_seq, &jiffies_lock);
46
47#if (BITS_PER_LONG < 64)
48u64 get_jiffies_64(void)
49{
50 unsigned int seq;
51 u64 ret;
52
53 do {
54 seq = read_seqcount_begin(&jiffies_seq);
55 ret = jiffies_64;
56 } while (read_seqcount_retry(&jiffies_seq, seq));
57 return ret;
58}
59EXPORT_SYMBOL(get_jiffies_64);
60#endif
61
62EXPORT_SYMBOL(jiffies);
63
64static int __init init_jiffies_clocksource(void)
65{
66 return __clocksource_register(&clocksource_jiffies);
67}
68
69core_initcall(init_jiffies_clocksource);
70
71struct clocksource * __init __weak clocksource_default_clock(void)
72{
73 return &clocksource_jiffies;
74}
75
76static struct clocksource refined_jiffies;
77
78int register_refined_jiffies(long cycles_per_second)
79{
80 u64 nsec_per_tick, shift_hz;
81 long cycles_per_tick;
82
83
84
85 refined_jiffies = clocksource_jiffies;
86 refined_jiffies.name = "refined-jiffies";
87 refined_jiffies.rating++;
88
89
90 cycles_per_tick = (cycles_per_second + HZ/2)/HZ;
91
92 shift_hz = (u64)cycles_per_second << 8;
93 shift_hz += cycles_per_tick/2;
94 do_div(shift_hz, cycles_per_tick);
95
96 nsec_per_tick = (u64)NSEC_PER_SEC << 8;
97 nsec_per_tick += (u32)shift_hz/2;
98 do_div(nsec_per_tick, (u32)shift_hz);
99
100 refined_jiffies.mult = ((u32)nsec_per_tick) << JIFFIES_SHIFT;
101
102 __clocksource_register(&refined_jiffies);
103 return 0;
104}
105