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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * x86 APERF/MPERF KHz calculation for
4 * /sys/.../cpufreq/scaling_cur_freq
5 *
6 * Copyright (C) 2017 Intel Corp.
7 * Author: Len Brown <len.brown@intel.com>
8 */
9
10#include <linux/delay.h>
11#include <linux/ktime.h>
12#include <linux/math64.h>
13#include <linux/percpu.h>
14#include <linux/cpufreq.h>
15#include <linux/smp.h>
16#include <linux/sched/isolation.h>
17
18#include "cpu.h"
19
20struct aperfmperf_sample {
21 unsigned int khz;
22 ktime_t time;
23 u64 aperf;
24 u64 mperf;
25};
26
27static DEFINE_PER_CPU(struct aperfmperf_sample, samples);
28
29#define APERFMPERF_CACHE_THRESHOLD_MS 10
30#define APERFMPERF_REFRESH_DELAY_MS 10
31#define APERFMPERF_STALE_THRESHOLD_MS 1000
32
33/*
34 * aperfmperf_snapshot_khz()
35 * On the current CPU, snapshot APERF, MPERF, and jiffies
36 * unless we already did it within 10ms
37 * calculate kHz, save snapshot
38 */
39static void aperfmperf_snapshot_khz(void *dummy)
40{
41 u64 aperf, aperf_delta;
42 u64 mperf, mperf_delta;
43 struct aperfmperf_sample *s = this_cpu_ptr(&samples);
44 unsigned long flags;
45
46 local_irq_save(flags);
47 rdmsrl(MSR_IA32_APERF, aperf);
48 rdmsrl(MSR_IA32_MPERF, mperf);
49 local_irq_restore(flags);
50
51 aperf_delta = aperf - s->aperf;
52 mperf_delta = mperf - s->mperf;
53
54 /*
55 * There is no architectural guarantee that MPERF
56 * increments faster than we can read it.
57 */
58 if (mperf_delta == 0)
59 return;
60
61 s->time = ktime_get();
62 s->aperf = aperf;
63 s->mperf = mperf;
64 s->khz = div64_u64((cpu_khz * aperf_delta), mperf_delta);
65}
66
67static bool aperfmperf_snapshot_cpu(int cpu, ktime_t now, bool wait)
68{
69 s64 time_delta = ktime_ms_delta(now, per_cpu(samples.time, cpu));
70
71 /* Don't bother re-computing within the cache threshold time. */
72 if (time_delta < APERFMPERF_CACHE_THRESHOLD_MS)
73 return true;
74
75 smp_call_function_single(cpu, aperfmperf_snapshot_khz, NULL, wait);
76
77 /* Return false if the previous iteration was too long ago. */
78 return time_delta <= APERFMPERF_STALE_THRESHOLD_MS;
79}
80
81unsigned int aperfmperf_get_khz(int cpu)
82{
83 if (!cpu_khz)
84 return 0;
85
86 if (!boot_cpu_has(X86_FEATURE_APERFMPERF))
87 return 0;
88
89 if (!housekeeping_cpu(cpu, HK_FLAG_MISC))
90 return 0;
91
92 aperfmperf_snapshot_cpu(cpu, ktime_get(), true);
93 return per_cpu(samples.khz, cpu);
94}
95
96void arch_freq_prepare_all(void)
97{
98 ktime_t now = ktime_get();
99 bool wait = false;
100 int cpu;
101
102 if (!cpu_khz)
103 return;
104
105 if (!boot_cpu_has(X86_FEATURE_APERFMPERF))
106 return;
107
108 for_each_online_cpu(cpu) {
109 if (!housekeeping_cpu(cpu, HK_FLAG_MISC))
110 continue;
111 if (!aperfmperf_snapshot_cpu(cpu, now, false))
112 wait = true;
113 }
114
115 if (wait)
116 msleep(APERFMPERF_REFRESH_DELAY_MS);
117}
118
119unsigned int arch_freq_get_on_cpu(int cpu)
120{
121 if (!cpu_khz)
122 return 0;
123
124 if (!boot_cpu_has(X86_FEATURE_APERFMPERF))
125 return 0;
126
127 if (!housekeeping_cpu(cpu, HK_FLAG_MISC))
128 return 0;
129
130 if (aperfmperf_snapshot_cpu(cpu, ktime_get(), true))
131 return per_cpu(samples.khz, cpu);
132
133 msleep(APERFMPERF_REFRESH_DELAY_MS);
134 smp_call_function_single(cpu, aperfmperf_snapshot_khz, NULL, 1);
135
136 return per_cpu(samples.khz, cpu);
137}
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * x86 APERF/MPERF KHz calculation for
4 * /sys/.../cpufreq/scaling_cur_freq
5 *
6 * Copyright (C) 2017 Intel Corp.
7 * Author: Len Brown <len.brown@intel.com>
8 */
9
10#include <linux/delay.h>
11#include <linux/ktime.h>
12#include <linux/math64.h>
13#include <linux/percpu.h>
14#include <linux/cpufreq.h>
15#include <linux/smp.h>
16#include <linux/sched/isolation.h>
17#include <linux/rcupdate.h>
18
19#include "cpu.h"
20
21struct aperfmperf_sample {
22 unsigned int khz;
23 atomic_t scfpending;
24 ktime_t time;
25 u64 aperf;
26 u64 mperf;
27};
28
29static DEFINE_PER_CPU(struct aperfmperf_sample, samples);
30
31#define APERFMPERF_CACHE_THRESHOLD_MS 10
32#define APERFMPERF_REFRESH_DELAY_MS 10
33#define APERFMPERF_STALE_THRESHOLD_MS 1000
34
35/*
36 * aperfmperf_snapshot_khz()
37 * On the current CPU, snapshot APERF, MPERF, and jiffies
38 * unless we already did it within 10ms
39 * calculate kHz, save snapshot
40 */
41static void aperfmperf_snapshot_khz(void *dummy)
42{
43 u64 aperf, aperf_delta;
44 u64 mperf, mperf_delta;
45 struct aperfmperf_sample *s = this_cpu_ptr(&samples);
46 unsigned long flags;
47
48 local_irq_save(flags);
49 rdmsrl(MSR_IA32_APERF, aperf);
50 rdmsrl(MSR_IA32_MPERF, mperf);
51 local_irq_restore(flags);
52
53 aperf_delta = aperf - s->aperf;
54 mperf_delta = mperf - s->mperf;
55
56 /*
57 * There is no architectural guarantee that MPERF
58 * increments faster than we can read it.
59 */
60 if (mperf_delta == 0)
61 return;
62
63 s->time = ktime_get();
64 s->aperf = aperf;
65 s->mperf = mperf;
66 s->khz = div64_u64((cpu_khz * aperf_delta), mperf_delta);
67 atomic_set_release(&s->scfpending, 0);
68}
69
70static bool aperfmperf_snapshot_cpu(int cpu, ktime_t now, bool wait)
71{
72 s64 time_delta = ktime_ms_delta(now, per_cpu(samples.time, cpu));
73 struct aperfmperf_sample *s = per_cpu_ptr(&samples, cpu);
74
75 /* Don't bother re-computing within the cache threshold time. */
76 if (time_delta < APERFMPERF_CACHE_THRESHOLD_MS)
77 return true;
78
79 if (!atomic_xchg(&s->scfpending, 1) || wait)
80 smp_call_function_single(cpu, aperfmperf_snapshot_khz, NULL, wait);
81
82 /* Return false if the previous iteration was too long ago. */
83 return time_delta <= APERFMPERF_STALE_THRESHOLD_MS;
84}
85
86unsigned int aperfmperf_get_khz(int cpu)
87{
88 if (!cpu_khz)
89 return 0;
90
91 if (!boot_cpu_has(X86_FEATURE_APERFMPERF))
92 return 0;
93
94 if (!housekeeping_cpu(cpu, HK_FLAG_MISC))
95 return 0;
96
97 if (rcu_is_idle_cpu(cpu))
98 return 0; /* Idle CPUs are completely uninteresting. */
99
100 aperfmperf_snapshot_cpu(cpu, ktime_get(), true);
101 return per_cpu(samples.khz, cpu);
102}
103
104void arch_freq_prepare_all(void)
105{
106 ktime_t now = ktime_get();
107 bool wait = false;
108 int cpu;
109
110 if (!cpu_khz)
111 return;
112
113 if (!boot_cpu_has(X86_FEATURE_APERFMPERF))
114 return;
115
116 for_each_online_cpu(cpu) {
117 if (!housekeeping_cpu(cpu, HK_FLAG_MISC))
118 continue;
119 if (rcu_is_idle_cpu(cpu))
120 continue; /* Idle CPUs are completely uninteresting. */
121 if (!aperfmperf_snapshot_cpu(cpu, now, false))
122 wait = true;
123 }
124
125 if (wait)
126 msleep(APERFMPERF_REFRESH_DELAY_MS);
127}
128
129unsigned int arch_freq_get_on_cpu(int cpu)
130{
131 struct aperfmperf_sample *s = per_cpu_ptr(&samples, cpu);
132
133 if (!cpu_khz)
134 return 0;
135
136 if (!boot_cpu_has(X86_FEATURE_APERFMPERF))
137 return 0;
138
139 if (!housekeeping_cpu(cpu, HK_FLAG_MISC))
140 return 0;
141
142 if (aperfmperf_snapshot_cpu(cpu, ktime_get(), true))
143 return per_cpu(samples.khz, cpu);
144
145 msleep(APERFMPERF_REFRESH_DELAY_MS);
146 atomic_set(&s->scfpending, 1);
147 smp_mb(); /* ->scfpending before smp_call_function_single(). */
148 smp_call_function_single(cpu, aperfmperf_snapshot_khz, NULL, 1);
149
150 return per_cpu(samples.khz, cpu);
151}