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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#include <linux/cpufreq.h>
10#include <linux/delay.h>
11#include <linux/ktime.h>
12#include <linux/math64.h>
13#include <linux/percpu.h>
14#include <linux/rcupdate.h>
15#include <linux/sched/isolation.h>
16#include <linux/sched/topology.h>
17#include <linux/smp.h>
18#include <linux/syscore_ops.h>
19
20#include <asm/cpu.h>
21#include <asm/cpu_device_id.h>
22#include <asm/intel-family.h>
23
24#include "cpu.h"
25
26struct aperfmperf {
27 seqcount_t seq;
28 unsigned long last_update;
29 u64 acnt;
30 u64 mcnt;
31 u64 aperf;
32 u64 mperf;
33};
34
35static DEFINE_PER_CPU_SHARED_ALIGNED(struct aperfmperf, cpu_samples) = {
36 .seq = SEQCNT_ZERO(cpu_samples.seq)
37};
38
39static void init_counter_refs(void)
40{
41 u64 aperf, mperf;
42
43 rdmsrl(MSR_IA32_APERF, aperf);
44 rdmsrl(MSR_IA32_MPERF, mperf);
45
46 this_cpu_write(cpu_samples.aperf, aperf);
47 this_cpu_write(cpu_samples.mperf, mperf);
48}
49
50#if defined(CONFIG_X86_64) && defined(CONFIG_SMP)
51/*
52 * APERF/MPERF frequency ratio computation.
53 *
54 * The scheduler wants to do frequency invariant accounting and needs a <1
55 * ratio to account for the 'current' frequency, corresponding to
56 * freq_curr / freq_max.
57 *
58 * Since the frequency freq_curr on x86 is controlled by micro-controller and
59 * our P-state setting is little more than a request/hint, we need to observe
60 * the effective frequency 'BusyMHz', i.e. the average frequency over a time
61 * interval after discarding idle time. This is given by:
62 *
63 * BusyMHz = delta_APERF / delta_MPERF * freq_base
64 *
65 * where freq_base is the max non-turbo P-state.
66 *
67 * The freq_max term has to be set to a somewhat arbitrary value, because we
68 * can't know which turbo states will be available at a given point in time:
69 * it all depends on the thermal headroom of the entire package. We set it to
70 * the turbo level with 4 cores active.
71 *
72 * Benchmarks show that's a good compromise between the 1C turbo ratio
73 * (freq_curr/freq_max would rarely reach 1) and something close to freq_base,
74 * which would ignore the entire turbo range (a conspicuous part, making
75 * freq_curr/freq_max always maxed out).
76 *
77 * An exception to the heuristic above is the Atom uarch, where we choose the
78 * highest turbo level for freq_max since Atom's are generally oriented towards
79 * power efficiency.
80 *
81 * Setting freq_max to anything less than the 1C turbo ratio makes the ratio
82 * freq_curr / freq_max to eventually grow >1, in which case we clip it to 1.
83 */
84
85DEFINE_STATIC_KEY_FALSE(arch_scale_freq_key);
86
87static u64 arch_turbo_freq_ratio = SCHED_CAPACITY_SCALE;
88static u64 arch_max_freq_ratio = SCHED_CAPACITY_SCALE;
89
90void arch_set_max_freq_ratio(bool turbo_disabled)
91{
92 arch_max_freq_ratio = turbo_disabled ? SCHED_CAPACITY_SCALE :
93 arch_turbo_freq_ratio;
94}
95EXPORT_SYMBOL_GPL(arch_set_max_freq_ratio);
96
97static bool __init turbo_disabled(void)
98{
99 u64 misc_en;
100 int err;
101
102 err = rdmsrl_safe(MSR_IA32_MISC_ENABLE, &misc_en);
103 if (err)
104 return false;
105
106 return (misc_en & MSR_IA32_MISC_ENABLE_TURBO_DISABLE);
107}
108
109static bool __init slv_set_max_freq_ratio(u64 *base_freq, u64 *turbo_freq)
110{
111 int err;
112
113 err = rdmsrl_safe(MSR_ATOM_CORE_RATIOS, base_freq);
114 if (err)
115 return false;
116
117 err = rdmsrl_safe(MSR_ATOM_CORE_TURBO_RATIOS, turbo_freq);
118 if (err)
119 return false;
120
121 *base_freq = (*base_freq >> 16) & 0x3F; /* max P state */
122 *turbo_freq = *turbo_freq & 0x3F; /* 1C turbo */
123
124 return true;
125}
126
127#define X86_MATCH(model) \
128 X86_MATCH_VENDOR_FAM_MODEL_FEATURE(INTEL, 6, \
129 INTEL_FAM6_##model, X86_FEATURE_APERFMPERF, NULL)
130
131static const struct x86_cpu_id has_knl_turbo_ratio_limits[] __initconst = {
132 X86_MATCH(XEON_PHI_KNL),
133 X86_MATCH(XEON_PHI_KNM),
134 {}
135};
136
137static const struct x86_cpu_id has_skx_turbo_ratio_limits[] __initconst = {
138 X86_MATCH(SKYLAKE_X),
139 {}
140};
141
142static const struct x86_cpu_id has_glm_turbo_ratio_limits[] __initconst = {
143 X86_MATCH(ATOM_GOLDMONT),
144 X86_MATCH(ATOM_GOLDMONT_D),
145 X86_MATCH(ATOM_GOLDMONT_PLUS),
146 {}
147};
148
149static bool __init knl_set_max_freq_ratio(u64 *base_freq, u64 *turbo_freq,
150 int num_delta_fratio)
151{
152 int fratio, delta_fratio, found;
153 int err, i;
154 u64 msr;
155
156 err = rdmsrl_safe(MSR_PLATFORM_INFO, base_freq);
157 if (err)
158 return false;
159
160 *base_freq = (*base_freq >> 8) & 0xFF; /* max P state */
161
162 err = rdmsrl_safe(MSR_TURBO_RATIO_LIMIT, &msr);
163 if (err)
164 return false;
165
166 fratio = (msr >> 8) & 0xFF;
167 i = 16;
168 found = 0;
169 do {
170 if (found >= num_delta_fratio) {
171 *turbo_freq = fratio;
172 return true;
173 }
174
175 delta_fratio = (msr >> (i + 5)) & 0x7;
176
177 if (delta_fratio) {
178 found += 1;
179 fratio -= delta_fratio;
180 }
181
182 i += 8;
183 } while (i < 64);
184
185 return true;
186}
187
188static bool __init skx_set_max_freq_ratio(u64 *base_freq, u64 *turbo_freq, int size)
189{
190 u64 ratios, counts;
191 u32 group_size;
192 int err, i;
193
194 err = rdmsrl_safe(MSR_PLATFORM_INFO, base_freq);
195 if (err)
196 return false;
197
198 *base_freq = (*base_freq >> 8) & 0xFF; /* max P state */
199
200 err = rdmsrl_safe(MSR_TURBO_RATIO_LIMIT, &ratios);
201 if (err)
202 return false;
203
204 err = rdmsrl_safe(MSR_TURBO_RATIO_LIMIT1, &counts);
205 if (err)
206 return false;
207
208 for (i = 0; i < 64; i += 8) {
209 group_size = (counts >> i) & 0xFF;
210 if (group_size >= size) {
211 *turbo_freq = (ratios >> i) & 0xFF;
212 return true;
213 }
214 }
215
216 return false;
217}
218
219static bool __init core_set_max_freq_ratio(u64 *base_freq, u64 *turbo_freq)
220{
221 u64 msr;
222 int err;
223
224 err = rdmsrl_safe(MSR_PLATFORM_INFO, base_freq);
225 if (err)
226 return false;
227
228 err = rdmsrl_safe(MSR_TURBO_RATIO_LIMIT, &msr);
229 if (err)
230 return false;
231
232 *base_freq = (*base_freq >> 8) & 0xFF; /* max P state */
233 *turbo_freq = (msr >> 24) & 0xFF; /* 4C turbo */
234
235 /* The CPU may have less than 4 cores */
236 if (!*turbo_freq)
237 *turbo_freq = msr & 0xFF; /* 1C turbo */
238
239 return true;
240}
241
242static bool __init intel_set_max_freq_ratio(void)
243{
244 u64 base_freq, turbo_freq;
245 u64 turbo_ratio;
246
247 if (slv_set_max_freq_ratio(&base_freq, &turbo_freq))
248 goto out;
249
250 if (x86_match_cpu(has_glm_turbo_ratio_limits) &&
251 skx_set_max_freq_ratio(&base_freq, &turbo_freq, 1))
252 goto out;
253
254 if (x86_match_cpu(has_knl_turbo_ratio_limits) &&
255 knl_set_max_freq_ratio(&base_freq, &turbo_freq, 1))
256 goto out;
257
258 if (x86_match_cpu(has_skx_turbo_ratio_limits) &&
259 skx_set_max_freq_ratio(&base_freq, &turbo_freq, 4))
260 goto out;
261
262 if (core_set_max_freq_ratio(&base_freq, &turbo_freq))
263 goto out;
264
265 return false;
266
267out:
268 /*
269 * Some hypervisors advertise X86_FEATURE_APERFMPERF
270 * but then fill all MSR's with zeroes.
271 * Some CPUs have turbo boost but don't declare any turbo ratio
272 * in MSR_TURBO_RATIO_LIMIT.
273 */
274 if (!base_freq || !turbo_freq) {
275 pr_debug("Couldn't determine cpu base or turbo frequency, necessary for scale-invariant accounting.\n");
276 return false;
277 }
278
279 turbo_ratio = div_u64(turbo_freq * SCHED_CAPACITY_SCALE, base_freq);
280 if (!turbo_ratio) {
281 pr_debug("Non-zero turbo and base frequencies led to a 0 ratio.\n");
282 return false;
283 }
284
285 arch_turbo_freq_ratio = turbo_ratio;
286 arch_set_max_freq_ratio(turbo_disabled());
287
288 return true;
289}
290
291#ifdef CONFIG_PM_SLEEP
292static struct syscore_ops freq_invariance_syscore_ops = {
293 .resume = init_counter_refs,
294};
295
296static void register_freq_invariance_syscore_ops(void)
297{
298 register_syscore_ops(&freq_invariance_syscore_ops);
299}
300#else
301static inline void register_freq_invariance_syscore_ops(void) {}
302#endif
303
304static void freq_invariance_enable(void)
305{
306 if (static_branch_unlikely(&arch_scale_freq_key)) {
307 WARN_ON_ONCE(1);
308 return;
309 }
310 static_branch_enable(&arch_scale_freq_key);
311 register_freq_invariance_syscore_ops();
312 pr_info("Estimated ratio of average max frequency by base frequency (times 1024): %llu\n", arch_max_freq_ratio);
313}
314
315void freq_invariance_set_perf_ratio(u64 ratio, bool turbo_disabled)
316{
317 arch_turbo_freq_ratio = ratio;
318 arch_set_max_freq_ratio(turbo_disabled);
319 freq_invariance_enable();
320}
321
322static void __init bp_init_freq_invariance(void)
323{
324 if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
325 return;
326
327 if (intel_set_max_freq_ratio())
328 freq_invariance_enable();
329}
330
331static void disable_freq_invariance_workfn(struct work_struct *work)
332{
333 int cpu;
334
335 static_branch_disable(&arch_scale_freq_key);
336
337 /*
338 * Set arch_freq_scale to a default value on all cpus
339 * This negates the effect of scaling
340 */
341 for_each_possible_cpu(cpu)
342 per_cpu(arch_freq_scale, cpu) = SCHED_CAPACITY_SCALE;
343}
344
345static DECLARE_WORK(disable_freq_invariance_work,
346 disable_freq_invariance_workfn);
347
348DEFINE_PER_CPU(unsigned long, arch_freq_scale) = SCHED_CAPACITY_SCALE;
349
350static void scale_freq_tick(u64 acnt, u64 mcnt)
351{
352 u64 freq_scale;
353
354 if (!arch_scale_freq_invariant())
355 return;
356
357 if (check_shl_overflow(acnt, 2*SCHED_CAPACITY_SHIFT, &acnt))
358 goto error;
359
360 if (check_mul_overflow(mcnt, arch_max_freq_ratio, &mcnt) || !mcnt)
361 goto error;
362
363 freq_scale = div64_u64(acnt, mcnt);
364 if (!freq_scale)
365 goto error;
366
367 if (freq_scale > SCHED_CAPACITY_SCALE)
368 freq_scale = SCHED_CAPACITY_SCALE;
369
370 this_cpu_write(arch_freq_scale, freq_scale);
371 return;
372
373error:
374 pr_warn("Scheduler frequency invariance went wobbly, disabling!\n");
375 schedule_work(&disable_freq_invariance_work);
376}
377#else
378static inline void bp_init_freq_invariance(void) { }
379static inline void scale_freq_tick(u64 acnt, u64 mcnt) { }
380#endif /* CONFIG_X86_64 && CONFIG_SMP */
381
382void arch_scale_freq_tick(void)
383{
384 struct aperfmperf *s = this_cpu_ptr(&cpu_samples);
385 u64 acnt, mcnt, aperf, mperf;
386
387 if (!cpu_feature_enabled(X86_FEATURE_APERFMPERF))
388 return;
389
390 rdmsrl(MSR_IA32_APERF, aperf);
391 rdmsrl(MSR_IA32_MPERF, mperf);
392 acnt = aperf - s->aperf;
393 mcnt = mperf - s->mperf;
394
395 s->aperf = aperf;
396 s->mperf = mperf;
397
398 raw_write_seqcount_begin(&s->seq);
399 s->last_update = jiffies;
400 s->acnt = acnt;
401 s->mcnt = mcnt;
402 raw_write_seqcount_end(&s->seq);
403
404 scale_freq_tick(acnt, mcnt);
405}
406
407/*
408 * Discard samples older than the define maximum sample age of 20ms. There
409 * is no point in sending IPIs in such a case. If the scheduler tick was
410 * not running then the CPU is either idle or isolated.
411 */
412#define MAX_SAMPLE_AGE ((unsigned long)HZ / 50)
413
414unsigned int arch_freq_get_on_cpu(int cpu)
415{
416 struct aperfmperf *s = per_cpu_ptr(&cpu_samples, cpu);
417 unsigned int seq, freq;
418 unsigned long last;
419 u64 acnt, mcnt;
420
421 if (!cpu_feature_enabled(X86_FEATURE_APERFMPERF))
422 goto fallback;
423
424 do {
425 seq = raw_read_seqcount_begin(&s->seq);
426 last = s->last_update;
427 acnt = s->acnt;
428 mcnt = s->mcnt;
429 } while (read_seqcount_retry(&s->seq, seq));
430
431 /*
432 * Bail on invalid count and when the last update was too long ago,
433 * which covers idle and NOHZ full CPUs.
434 */
435 if (!mcnt || (jiffies - last) > MAX_SAMPLE_AGE)
436 goto fallback;
437
438 return div64_u64((cpu_khz * acnt), mcnt);
439
440fallback:
441 freq = cpufreq_quick_get(cpu);
442 return freq ? freq : cpu_khz;
443}
444
445static int __init bp_init_aperfmperf(void)
446{
447 if (!cpu_feature_enabled(X86_FEATURE_APERFMPERF))
448 return 0;
449
450 init_counter_refs();
451 bp_init_freq_invariance();
452 return 0;
453}
454early_initcall(bp_init_aperfmperf);
455
456void ap_init_aperfmperf(void)
457{
458 if (cpu_feature_enabled(X86_FEATURE_APERFMPERF))
459 init_counter_refs();
460}