Commit | Line | Data |
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112f38a4 RK |
1 | /* |
2 | * sched_clock.c: support for extending counters to full 64-bit ns counter | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License version 2 as | |
6 | * published by the Free Software Foundation. | |
7 | */ | |
8 | #include <linux/clocksource.h> | |
9 | #include <linux/init.h> | |
10 | #include <linux/jiffies.h> | |
11 | #include <linux/kernel.h> | |
a42c3629 | 12 | #include <linux/moduleparam.h> |
112f38a4 | 13 | #include <linux/sched.h> |
f153d017 | 14 | #include <linux/syscore_ops.h> |
112f38a4 | 15 | #include <linux/timer.h> |
38ff87f7 | 16 | #include <linux/sched_clock.h> |
85c3d2dd | 17 | #include <linux/seqlock.h> |
112f38a4 | 18 | |
2f0778af MZ |
19 | struct clock_data { |
20 | u64 epoch_ns; | |
21 | u32 epoch_cyc; | |
85c3d2dd | 22 | seqcount_t seq; |
c115739d | 23 | unsigned long rate; |
2f0778af MZ |
24 | u32 mult; |
25 | u32 shift; | |
237ec6f2 | 26 | bool suspended; |
2f0778af MZ |
27 | }; |
28 | ||
112f38a4 RK |
29 | static void sched_clock_poll(unsigned long wrap_ticks); |
30 | static DEFINE_TIMER(sched_clock_timer, sched_clock_poll, 0, 0); | |
a42c3629 RK |
31 | static int irqtime = -1; |
32 | ||
33 | core_param(irqtime, irqtime, int, 0400); | |
2f0778af MZ |
34 | |
35 | static struct clock_data cd = { | |
36 | .mult = NSEC_PER_SEC / HZ, | |
37 | }; | |
38 | ||
39 | static u32 __read_mostly sched_clock_mask = 0xffffffff; | |
40 | ||
41 | static u32 notrace jiffy_sched_clock_read(void) | |
42 | { | |
43 | return (u32)(jiffies - INITIAL_JIFFIES); | |
44 | } | |
45 | ||
46 | static u32 __read_mostly (*read_sched_clock)(void) = jiffy_sched_clock_read; | |
47 | ||
cea15092 | 48 | static inline u64 notrace cyc_to_ns(u64 cyc, u32 mult, u32 shift) |
2f0778af MZ |
49 | { |
50 | return (cyc * mult) >> shift; | |
51 | } | |
52 | ||
336ae118 | 53 | static unsigned long long notrace sched_clock_32(void) |
2f0778af MZ |
54 | { |
55 | u64 epoch_ns; | |
56 | u32 epoch_cyc; | |
336ae118 | 57 | u32 cyc; |
85c3d2dd | 58 | unsigned long seq; |
336ae118 SB |
59 | |
60 | if (cd.suspended) | |
61 | return cd.epoch_ns; | |
2f0778af | 62 | |
2f0778af | 63 | do { |
85c3d2dd | 64 | seq = read_seqcount_begin(&cd.seq); |
2f0778af | 65 | epoch_cyc = cd.epoch_cyc; |
2f0778af | 66 | epoch_ns = cd.epoch_ns; |
85c3d2dd | 67 | } while (read_seqcount_retry(&cd.seq, seq)); |
2f0778af | 68 | |
336ae118 SB |
69 | cyc = read_sched_clock(); |
70 | cyc = (cyc - epoch_cyc) & sched_clock_mask; | |
71 | return epoch_ns + cyc_to_ns(cyc, cd.mult, cd.shift); | |
2f0778af MZ |
72 | } |
73 | ||
74 | /* | |
75 | * Atomically update the sched_clock epoch. | |
76 | */ | |
77 | static void notrace update_sched_clock(void) | |
78 | { | |
79 | unsigned long flags; | |
80 | u32 cyc; | |
81 | u64 ns; | |
82 | ||
83 | cyc = read_sched_clock(); | |
84 | ns = cd.epoch_ns + | |
85 | cyc_to_ns((cyc - cd.epoch_cyc) & sched_clock_mask, | |
86 | cd.mult, cd.shift); | |
85c3d2dd | 87 | |
2f0778af | 88 | raw_local_irq_save(flags); |
85c3d2dd | 89 | write_seqcount_begin(&cd.seq); |
2f0778af | 90 | cd.epoch_ns = ns; |
7c4e9ced | 91 | cd.epoch_cyc = cyc; |
85c3d2dd | 92 | write_seqcount_end(&cd.seq); |
2f0778af MZ |
93 | raw_local_irq_restore(flags); |
94 | } | |
112f38a4 RK |
95 | |
96 | static void sched_clock_poll(unsigned long wrap_ticks) | |
97 | { | |
98 | mod_timer(&sched_clock_timer, round_jiffies(jiffies + wrap_ticks)); | |
2f0778af | 99 | update_sched_clock(); |
112f38a4 RK |
100 | } |
101 | ||
2f0778af | 102 | void __init setup_sched_clock(u32 (*read)(void), int bits, unsigned long rate) |
112f38a4 RK |
103 | { |
104 | unsigned long r, w; | |
105 | u64 res, wrap; | |
106 | char r_unit; | |
107 | ||
c115739d RH |
108 | if (cd.rate > rate) |
109 | return; | |
110 | ||
2f0778af MZ |
111 | BUG_ON(bits > 32); |
112 | WARN_ON(!irqs_disabled()); | |
2f0778af MZ |
113 | read_sched_clock = read; |
114 | sched_clock_mask = (1 << bits) - 1; | |
c115739d | 115 | cd.rate = rate; |
112f38a4 RK |
116 | |
117 | /* calculate the mult/shift to convert counter ticks to ns. */ | |
2f0778af | 118 | clocks_calc_mult_shift(&cd.mult, &cd.shift, rate, NSEC_PER_SEC, 0); |
112f38a4 RK |
119 | |
120 | r = rate; | |
121 | if (r >= 4000000) { | |
122 | r /= 1000000; | |
123 | r_unit = 'M'; | |
2f0778af | 124 | } else if (r >= 1000) { |
112f38a4 RK |
125 | r /= 1000; |
126 | r_unit = 'k'; | |
2f0778af MZ |
127 | } else |
128 | r_unit = ' '; | |
112f38a4 RK |
129 | |
130 | /* calculate how many ns until we wrap */ | |
2f0778af | 131 | wrap = cyc_to_ns((1ULL << bits) - 1, cd.mult, cd.shift); |
112f38a4 RK |
132 | do_div(wrap, NSEC_PER_MSEC); |
133 | w = wrap; | |
134 | ||
135 | /* calculate the ns resolution of this counter */ | |
2f0778af | 136 | res = cyc_to_ns(1ULL, cd.mult, cd.shift); |
112f38a4 | 137 | pr_info("sched_clock: %u bits at %lu%cHz, resolution %lluns, wraps every %lums\n", |
2f0778af | 138 | bits, r, r_unit, res, w); |
112f38a4 RK |
139 | |
140 | /* | |
141 | * Start the timer to keep sched_clock() properly updated and | |
142 | * sets the initial epoch. | |
143 | */ | |
144 | sched_clock_timer.data = msecs_to_jiffies(w - (w / 10)); | |
2f0778af | 145 | update_sched_clock(); |
112f38a4 RK |
146 | |
147 | /* | |
148 | * Ensure that sched_clock() starts off at 0ns | |
149 | */ | |
2f0778af MZ |
150 | cd.epoch_ns = 0; |
151 | ||
a42c3629 RK |
152 | /* Enable IRQ time accounting if we have a fast enough sched_clock */ |
153 | if (irqtime > 0 || (irqtime == -1 && rate >= 1000000)) | |
154 | enable_sched_clock_irqtime(); | |
155 | ||
2f0778af MZ |
156 | pr_debug("Registered %pF as sched_clock source\n", read); |
157 | } | |
158 | ||
7e48c0b9 RH |
159 | unsigned long long __read_mostly (*sched_clock_func)(void) = sched_clock_32; |
160 | ||
161 | unsigned long long notrace sched_clock(void) | |
162 | { | |
163 | return sched_clock_func(); | |
164 | } | |
165 | ||
211baa70 RK |
166 | void __init sched_clock_postinit(void) |
167 | { | |
2f0778af MZ |
168 | /* |
169 | * If no sched_clock function has been provided at that point, | |
170 | * make it the final one one. | |
171 | */ | |
172 | if (read_sched_clock == jiffy_sched_clock_read) | |
173 | setup_sched_clock(jiffy_sched_clock_read, 32, HZ); | |
174 | ||
211baa70 RK |
175 | sched_clock_poll(sched_clock_timer.data); |
176 | } | |
f153d017 RK |
177 | |
178 | static int sched_clock_suspend(void) | |
179 | { | |
180 | sched_clock_poll(sched_clock_timer.data); | |
6a4dae5e | 181 | cd.suspended = true; |
f153d017 RK |
182 | return 0; |
183 | } | |
184 | ||
237ec6f2 CC |
185 | static void sched_clock_resume(void) |
186 | { | |
6a4dae5e | 187 | cd.epoch_cyc = read_sched_clock(); |
6a4dae5e | 188 | cd.suspended = false; |
237ec6f2 CC |
189 | } |
190 | ||
f153d017 RK |
191 | static struct syscore_ops sched_clock_ops = { |
192 | .suspend = sched_clock_suspend, | |
237ec6f2 | 193 | .resume = sched_clock_resume, |
f153d017 RK |
194 | }; |
195 | ||
196 | static int __init sched_clock_syscore_init(void) | |
197 | { | |
198 | register_syscore_ops(&sched_clock_ops); | |
199 | return 0; | |
200 | } | |
201 | device_initcall(sched_clock_syscore_init); |