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author | Russell King <rmk+kernel@armlinux.org.uk> | 2017-09-09 16:34:41 +0100 |
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committer | Russell King <rmk+kernel@armlinux.org.uk> | 2017-09-09 16:34:41 +0100 |
commit | e558bdc21ae1f0db520eccd84015e17d8a589973 (patch) | |
tree | b436123bd52f267b8c7f361618cded3e1e4421ea /arch/x86/kernel/cpu/aperfmperf.c | |
parent | 746a272e44141af24a02f6c9b0f65f4c4598ed42 (diff) | |
parent | 9a3dc3186fc3795e076a4122da9e0258651a9631 (diff) | |
download | op-kernel-dev-e558bdc21ae1f0db520eccd84015e17d8a589973.zip op-kernel-dev-e558bdc21ae1f0db520eccd84015e17d8a589973.tar.gz |
Merge branches 'fixes' and 'misc' into for-linus
Diffstat (limited to 'arch/x86/kernel/cpu/aperfmperf.c')
-rw-r--r-- | arch/x86/kernel/cpu/aperfmperf.c | 79 |
1 files changed, 79 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/aperfmperf.c b/arch/x86/kernel/cpu/aperfmperf.c new file mode 100644 index 0000000..d869c86 --- /dev/null +++ b/arch/x86/kernel/cpu/aperfmperf.c @@ -0,0 +1,79 @@ +/* + * x86 APERF/MPERF KHz calculation for + * /sys/.../cpufreq/scaling_cur_freq + * + * Copyright (C) 2017 Intel Corp. + * Author: Len Brown <len.brown@intel.com> + * + * This file is licensed under GPLv2. + */ + +#include <linux/jiffies.h> +#include <linux/math64.h> +#include <linux/percpu.h> +#include <linux/smp.h> + +struct aperfmperf_sample { + unsigned int khz; + unsigned long jiffies; + u64 aperf; + u64 mperf; +}; + +static DEFINE_PER_CPU(struct aperfmperf_sample, samples); + +/* + * 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); + + /* Don't bother re-computing within 10 ms */ + if (time_before(jiffies, s->jiffies + HZ/100)) + return; + + rdmsrl(MSR_IA32_APERF, aperf); + rdmsrl(MSR_IA32_MPERF, mperf); + + 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; + + /* + * if (cpu_khz * aperf_delta) fits into ULLONG_MAX, then + * khz = (cpu_khz * aperf_delta) / mperf_delta + */ + if (div64_u64(ULLONG_MAX, cpu_khz) > aperf_delta) + s->khz = div64_u64((cpu_khz * aperf_delta), mperf_delta); + else /* khz = aperf_delta / (mperf_delta / cpu_khz) */ + s->khz = div64_u64(aperf_delta, + div64_u64(mperf_delta, cpu_khz)); + s->jiffies = jiffies; + s->aperf = aperf; + s->mperf = mperf; +} + +unsigned int arch_freq_get_on_cpu(int cpu) +{ + if (!cpu_khz) + return 0; + + if (!static_cpu_has(X86_FEATURE_APERFMPERF)) + return 0; + + smp_call_function_single(cpu, aperfmperf_snapshot_khz, NULL, 1); + + return per_cpu(samples.khz, cpu); +} |