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