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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/syscore_ops.h>
17#include <linux/hrtimer.h>
18#include <linux/sched_clock.h>
19#include <linux/seqlock.h>
20#include <linux/bitops.h>
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38struct clock_read_data {
39 u64 epoch_ns;
40 u64 epoch_cyc;
41 u64 sched_clock_mask;
42 u64 (*read_sched_clock)(void);
43 u32 mult;
44 u32 shift;
45};
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62struct clock_data {
63 seqcount_t seq;
64 struct clock_read_data read_data[2];
65 ktime_t wrap_kt;
66 unsigned long rate;
67
68 u64 (*actual_read_sched_clock)(void);
69};
70
71static struct hrtimer sched_clock_timer;
72static int irqtime = -1;
73
74core_param(irqtime, irqtime, int, 0400);
75
76static u64 notrace jiffy_sched_clock_read(void)
77{
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81
82 return (u64)(jiffies - INITIAL_JIFFIES);
83}
84
85static struct clock_data cd ____cacheline_aligned = {
86 .read_data[0] = { .mult = NSEC_PER_SEC / HZ,
87 .read_sched_clock = jiffy_sched_clock_read, },
88 .actual_read_sched_clock = jiffy_sched_clock_read,
89};
90
91static inline u64 notrace cyc_to_ns(u64 cyc, u32 mult, u32 shift)
92{
93 return (cyc * mult) >> shift;
94}
95
96unsigned long long notrace sched_clock(void)
97{
98 u64 cyc, res;
99 unsigned long seq;
100 struct clock_read_data *rd;
101
102 do {
103 seq = raw_read_seqcount(&cd.seq);
104 rd = cd.read_data + (seq & 1);
105
106 cyc = (rd->read_sched_clock() - rd->epoch_cyc) &
107 rd->sched_clock_mask;
108 res = rd->epoch_ns + cyc_to_ns(cyc, rd->mult, rd->shift);
109 } while (read_seqcount_retry(&cd.seq, seq));
110
111 return res;
112}
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123
124static void update_clock_read_data(struct clock_read_data *rd)
125{
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127 cd.read_data[1] = *rd;
128
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130 raw_write_seqcount_latch(&cd.seq);
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133 cd.read_data[0] = *rd;
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135
136 raw_write_seqcount_latch(&cd.seq);
137}
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141
142static void update_sched_clock(void)
143{
144 u64 cyc;
145 u64 ns;
146 struct clock_read_data rd;
147
148 rd = cd.read_data[0];
149
150 cyc = cd.actual_read_sched_clock();
151 ns = rd.epoch_ns + cyc_to_ns((cyc - rd.epoch_cyc) & rd.sched_clock_mask, rd.mult, rd.shift);
152
153 rd.epoch_ns = ns;
154 rd.epoch_cyc = cyc;
155
156 update_clock_read_data(&rd);
157}
158
159static enum hrtimer_restart sched_clock_poll(struct hrtimer *hrt)
160{
161 update_sched_clock();
162 hrtimer_forward_now(hrt, cd.wrap_kt);
163
164 return HRTIMER_RESTART;
165}
166
167void __init
168sched_clock_register(u64 (*read)(void), int bits, unsigned long rate)
169{
170 u64 res, wrap, new_mask, new_epoch, cyc, ns;
171 u32 new_mult, new_shift;
172 unsigned long r;
173 char r_unit;
174 struct clock_read_data rd;
175
176 if (cd.rate > rate)
177 return;
178
179 WARN_ON(!irqs_disabled());
180
181
182 clocks_calc_mult_shift(&new_mult, &new_shift, rate, NSEC_PER_SEC, 3600);
183
184 new_mask = CLOCKSOURCE_MASK(bits);
185 cd.rate = rate;
186
187
188 wrap = clocks_calc_max_nsecs(new_mult, new_shift, 0, new_mask, NULL);
189 cd.wrap_kt = ns_to_ktime(wrap);
190
191 rd = cd.read_data[0];
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194 new_epoch = read();
195 cyc = cd.actual_read_sched_clock();
196 ns = rd.epoch_ns + cyc_to_ns((cyc - rd.epoch_cyc) & rd.sched_clock_mask, rd.mult, rd.shift);
197 cd.actual_read_sched_clock = read;
198
199 rd.read_sched_clock = read;
200 rd.sched_clock_mask = new_mask;
201 rd.mult = new_mult;
202 rd.shift = new_shift;
203 rd.epoch_cyc = new_epoch;
204 rd.epoch_ns = ns;
205
206 update_clock_read_data(&rd);
207
208 r = rate;
209 if (r >= 4000000) {
210 r /= 1000000;
211 r_unit = 'M';
212 } else {
213 if (r >= 1000) {
214 r /= 1000;
215 r_unit = 'k';
216 } else {
217 r_unit = ' ';
218 }
219 }
220
221
222 res = cyc_to_ns(1ULL, new_mult, new_shift);
223
224 pr_info("sched_clock: %u bits at %lu%cHz, resolution %lluns, wraps every %lluns\n",
225 bits, r, r_unit, res, wrap);
226
227
228 if (irqtime > 0 || (irqtime == -1 && rate >= 1000000))
229 enable_sched_clock_irqtime();
230
231 pr_debug("Registered %pF as sched_clock source\n", read);
232}
233
234void __init sched_clock_postinit(void)
235{
236
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240 if (cd.actual_read_sched_clock == jiffy_sched_clock_read)
241 sched_clock_register(jiffy_sched_clock_read, BITS_PER_LONG, HZ);
242
243 update_sched_clock();
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249 hrtimer_init(&sched_clock_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
250 sched_clock_timer.function = sched_clock_poll;
251 hrtimer_start(&sched_clock_timer, cd.wrap_kt, HRTIMER_MODE_REL);
252}
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265static u64 notrace suspended_sched_clock_read(void)
266{
267 unsigned long seq = raw_read_seqcount(&cd.seq);
268
269 return cd.read_data[seq & 1].epoch_cyc;
270}
271
272static int sched_clock_suspend(void)
273{
274 struct clock_read_data *rd = &cd.read_data[0];
275
276 update_sched_clock();
277 hrtimer_cancel(&sched_clock_timer);
278 rd->read_sched_clock = suspended_sched_clock_read;
279
280 return 0;
281}
282
283static void sched_clock_resume(void)
284{
285 struct clock_read_data *rd = &cd.read_data[0];
286
287 rd->epoch_cyc = cd.actual_read_sched_clock();
288 hrtimer_start(&sched_clock_timer, cd.wrap_kt, HRTIMER_MODE_REL);
289 rd->read_sched_clock = cd.actual_read_sched_clock;
290}
291
292static struct syscore_ops sched_clock_ops = {
293 .suspend = sched_clock_suspend,
294 .resume = sched_clock_resume,
295};
296
297static int __init sched_clock_syscore_init(void)
298{
299 register_syscore_ops(&sched_clock_ops);
300
301 return 0;
302}
303device_initcall(sched_clock_syscore_init);
304