| // 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 "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; |
| |
| 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 (!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 (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); |
| } |