4 files changed, 93 insertions, 1 deletions

diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
index 52000010c62e..cdf82492b770 100644
--- a/arch/x86/kernel/cpu/Makefile
+++ b/arch/x86/kernel/cpu/Makefile
@@ -21,6 +21,7 @@ obj-y			+= common.o
 obj-y                   += rdrand.o
 obj-y                   += match.o
 obj-y                   += bugs.o
+obj-$(CONFIG_CPU_FREQ)  += aperfmperf.o
 
 obj-$(CONFIG_PROC_FS)   += proc.o
 obj-$(CONFIG_X86_FEATURE_NAMES) += capflags.o powerflags.o
diff --git a/arch/x86/kernel/cpu/aperfmperf.c b/arch/x86/kernel/cpu/aperfmperf.c
new file mode 100644
index 000000000000..d869c8671e36
--- /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);
+}
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 26b643d57847..6e7424d12de9 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -632,11 +632,21 @@ show_one(cpuinfo_transition_latency, cpuinfo.transition_latency);
 show_one(scaling_min_freq, min);
 show_one(scaling_max_freq, max);
 
+__weak unsigned int arch_freq_get_on_cpu(int cpu)
+{
+        return 0;
+}
+
 static ssize_t show_scaling_cur_freq(struct cpufreq_policy *policy, char *buf)
 {
         ssize_t ret;
+        unsigned int freq;
 
-        if (cpufreq_driver && cpufreq_driver->setpolicy && cpufreq_driver->get)
+        freq = arch_freq_get_on_cpu(policy->cpu);
+        if (freq)
+                ret = sprintf(buf, "%u\n", freq);
+        else if (cpufreq_driver && cpufreq_driver->setpolicy &&
+                        cpufreq_driver->get)
                 ret = sprintf(buf, "%u\n", cpufreq_driver->get(policy->cpu));
         else
                 ret = sprintf(buf, "%u\n", policy->cur);
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index a5ce0bbeadb5..905117bd5012 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -883,6 +883,8 @@ static inline bool policy_has_boost_freq(struct cpufreq_policy *policy)
 }
 #endif
 
+extern unsigned int arch_freq_get_on_cpu(int cpu);
+
 /* the following are really really optional */
 extern struct freq_attr cpufreq_freq_attr_scaling_available_freqs;
 extern struct freq_attr cpufreq_freq_attr_scaling_boost_freqs;