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9#include <linux/clocksource.h>
10#include <linux/init.h>
11#include <linux/jiffies.h>
12#include <linux/ktime.h>
13#include <linux/kernel.h>
14#include <linux/moduleparam.h>
15#include <linux/sched.h>
16#include <linux/sched/clock.h>
17#include <linux/syscore_ops.h>
18#include <linux/hrtimer.h>
19#include <linux/sched_clock.h>
20#include <linux/seqlock.h>
21#include <linux/bitops.h>
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39struct clock_read_data {
40 u64 epoch_ns;
41 u64 epoch_cyc;
42 u64 sched_clock_mask;
43 u64 (*read_sched_clock)(void);
44 u32 mult;
45 u32 shift;
46};
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63struct clock_data {
64 seqcount_t seq;
65 struct clock_read_data read_data[2];
66 ktime_t wrap_kt;
67 unsigned long rate;
68
69 u64 (*actual_read_sched_clock)(void);
70};
71
72static struct hrtimer sched_clock_timer;
73static int irqtime = -1;
74
75core_param(irqtime, irqtime, int, 0400);
76
77static u64 notrace jiffy_sched_clock_read(void)
78{
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83 return (u64)(jiffies - INITIAL_JIFFIES);
84}
85
86static struct clock_data cd ____cacheline_aligned = {
87 .read_data[0] = { .mult = NSEC_PER_SEC / HZ,
88 .read_sched_clock = jiffy_sched_clock_read, },
89 .actual_read_sched_clock = jiffy_sched_clock_read,
90};
91
92static inline u64 notrace cyc_to_ns(u64 cyc, u32 mult, u32 shift)
93{
94 return (cyc * mult) >> shift;
95}
96
97unsigned long long notrace sched_clock(void)
98{
99 u64 cyc, res;
100 unsigned long seq;
101 struct clock_read_data *rd;
102
103 do {
104 seq = raw_read_seqcount(&cd.seq);
105 rd = cd.read_data + (seq & 1);
106
107 cyc = (rd->read_sched_clock() - rd->epoch_cyc) &
108 rd->sched_clock_mask;
109 res = rd->epoch_ns + cyc_to_ns(cyc, rd->mult, rd->shift);
110 } while (read_seqcount_retry(&cd.seq, seq));
111
112 return res;
113}
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124
125static void update_clock_read_data(struct clock_read_data *rd)
126{
127
128 cd.read_data[1] = *rd;
129
130
131 raw_write_seqcount_latch(&cd.seq);
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134 cd.read_data[0] = *rd;
135
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137 raw_write_seqcount_latch(&cd.seq);
138}
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142
143static void update_sched_clock(void)
144{
145 u64 cyc;
146 u64 ns;
147 struct clock_read_data rd;
148
149 rd = cd.read_data[0];
150
151 cyc = cd.actual_read_sched_clock();
152 ns = rd.epoch_ns + cyc_to_ns((cyc - rd.epoch_cyc) & rd.sched_clock_mask, rd.mult, rd.shift);
153
154 rd.epoch_ns = ns;
155 rd.epoch_cyc = cyc;
156
157 update_clock_read_data(&rd);
158}
159
160static enum hrtimer_restart sched_clock_poll(struct hrtimer *hrt)
161{
162 update_sched_clock();
163 hrtimer_forward_now(hrt, cd.wrap_kt);
164
165 return HRTIMER_RESTART;
166}
167
168void __init
169sched_clock_register(u64 (*read)(void), int bits, unsigned long rate)
170{
171 u64 res, wrap, new_mask, new_epoch, cyc, ns;
172 u32 new_mult, new_shift;
173 unsigned long r;
174 char r_unit;
175 struct clock_read_data rd;
176
177 if (cd.rate > rate)
178 return;
179
180 WARN_ON(!irqs_disabled());
181
182
183 clocks_calc_mult_shift(&new_mult, &new_shift, rate, NSEC_PER_SEC, 3600);
184
185 new_mask = CLOCKSOURCE_MASK(bits);
186 cd.rate = rate;
187
188
189 wrap = clocks_calc_max_nsecs(new_mult, new_shift, 0, new_mask, NULL);
190 cd.wrap_kt = ns_to_ktime(wrap);
191
192 rd = cd.read_data[0];
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195 new_epoch = read();
196 cyc = cd.actual_read_sched_clock();
197 ns = rd.epoch_ns + cyc_to_ns((cyc - rd.epoch_cyc) & rd.sched_clock_mask, rd.mult, rd.shift);
198 cd.actual_read_sched_clock = read;
199
200 rd.read_sched_clock = read;
201 rd.sched_clock_mask = new_mask;
202 rd.mult = new_mult;
203 rd.shift = new_shift;
204 rd.epoch_cyc = new_epoch;
205 rd.epoch_ns = ns;
206
207 update_clock_read_data(&rd);
208
209 if (sched_clock_timer.function != NULL) {
210
211 hrtimer_start(&sched_clock_timer, cd.wrap_kt, HRTIMER_MODE_REL);
212 }
213
214 r = rate;
215 if (r >= 4000000) {
216 r /= 1000000;
217 r_unit = 'M';
218 } else {
219 if (r >= 1000) {
220 r /= 1000;
221 r_unit = 'k';
222 } else {
223 r_unit = ' ';
224 }
225 }
226
227
228 res = cyc_to_ns(1ULL, new_mult, new_shift);
229
230 pr_info("sched_clock: %u bits at %lu%cHz, resolution %lluns, wraps every %lluns\n",
231 bits, r, r_unit, res, wrap);
232
233
234 if (irqtime > 0 || (irqtime == -1 && rate >= 1000000))
235 enable_sched_clock_irqtime();
236
237 pr_debug("Registered %pF as sched_clock source\n", read);
238}
239
240void __init sched_clock_postinit(void)
241{
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246 if (cd.actual_read_sched_clock == jiffy_sched_clock_read)
247 sched_clock_register(jiffy_sched_clock_read, BITS_PER_LONG, HZ);
248
249 update_sched_clock();
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255 hrtimer_init(&sched_clock_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
256 sched_clock_timer.function = sched_clock_poll;
257 hrtimer_start(&sched_clock_timer, cd.wrap_kt, HRTIMER_MODE_REL);
258}
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271static u64 notrace suspended_sched_clock_read(void)
272{
273 unsigned long seq = raw_read_seqcount(&cd.seq);
274
275 return cd.read_data[seq & 1].epoch_cyc;
276}
277
278static int sched_clock_suspend(void)
279{
280 struct clock_read_data *rd = &cd.read_data[0];
281
282 update_sched_clock();
283 hrtimer_cancel(&sched_clock_timer);
284 rd->read_sched_clock = suspended_sched_clock_read;
285
286 return 0;
287}
288
289static void sched_clock_resume(void)
290{
291 struct clock_read_data *rd = &cd.read_data[0];
292
293 rd->epoch_cyc = cd.actual_read_sched_clock();
294 hrtimer_start(&sched_clock_timer, cd.wrap_kt, HRTIMER_MODE_REL);
295 rd->read_sched_clock = cd.actual_read_sched_clock;
296}
297
298static struct syscore_ops sched_clock_ops = {
299 .suspend = sched_clock_suspend,
300 .resume = sched_clock_resume,
301};
302
303static int __init sched_clock_syscore_init(void)
304{
305 register_syscore_ops(&sched_clock_ops);
306
307 return 0;
308}
309device_initcall(sched_clock_syscore_init);
310