cpufreq: AMD "frequency sensitivity feedback" powersave bias for ondemand governor

Future AMD processors, starting with Family 16h, can provide software
with feedback on how the workload may respond to frequency change --
memory-bound workloads will not benefit from higher frequency, where
as compute-bound workloads will. This patch enables this "frequency
sensitivity feedback" to aid the ondemand governor to make better
frequency change decisions by hooking into the powersave bias.

Signed-off-by: Jacob Shin <jacob.shin@amd.com>
Acked-by: Thomas Renninger <trenn@suse.de>
Acked-by: Borislav Petkov <bp@suse.de>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 148 insertions, 0 deletions

diff --git a/drivers/cpufreq/amd_freq_sensitivity.c b/drivers/cpufreq/amd_freq_sensitivity.c
new file mode 100644
index 000000000000..f6b79ab0070b
--- /dev/null
+++ b/drivers/cpufreq/amd_freq_sensitivity.c
@@ -0,0 +1,148 @@
+/*
+ * amd_freq_sensitivity.c: AMD frequency sensitivity feedback powersave bias
+ *                         for the ondemand governor.
+ *
+ * Copyright (C) 2013 Advanced Micro Devices, Inc.
+ *
+ * Author: Jacob Shin <jacob.shin@amd.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/percpu-defs.h>
+#include <linux/init.h>
+#include <linux/mod_devicetable.h>
+
+#include <asm/msr.h>
+#include <asm/cpufeature.h>
+
+#include "cpufreq_governor.h"
+
+#define MSR_AMD64_FREQ_SENSITIVITY_ACTUAL       0xc0010080
+#define MSR_AMD64_FREQ_SENSITIVITY_REFERENCE    0xc0010081
+#define CLASS_CODE_SHIFT                        56
+#define POWERSAVE_BIAS_MAX                      1000
+#define POWERSAVE_BIAS_DEF                      400
+
+struct cpu_data_t {
+        u64 actual;
+        u64 reference;
+        unsigned int freq_prev;
+};
+
+static DEFINE_PER_CPU(struct cpu_data_t, cpu_data);
+
+static unsigned int amd_powersave_bias_target(struct cpufreq_policy *policy,
+                                              unsigned int freq_next,
+                                              unsigned int relation)
+{
+        int sensitivity;
+        long d_actual, d_reference;
+        struct msr actual, reference;
+        struct cpu_data_t *data = &per_cpu(cpu_data, policy->cpu);
+        struct dbs_data *od_data = policy->governor_data;
+        struct od_dbs_tuners *od_tuners = od_data->tuners;
+        struct od_cpu_dbs_info_s *od_info =
+                od_data->cdata->get_cpu_dbs_info_s(policy->cpu);
+
+        if (!od_info->freq_table)
+                return freq_next;
+
+        rdmsr_on_cpu(policy->cpu, MSR_AMD64_FREQ_SENSITIVITY_ACTUAL,
+                &actual.l, &actual.h);
+        rdmsr_on_cpu(policy->cpu, MSR_AMD64_FREQ_SENSITIVITY_REFERENCE,
+                &reference.l, &reference.h);
+        actual.h &= 0x00ffffff;
+        reference.h &= 0x00ffffff;
+
+        /* counter wrapped around, so stay on current frequency */
+        if (actual.q < data->actual || reference.q < data->reference) {
+                freq_next = policy->cur;
+                goto out;
+        }
+
+        d_actual = actual.q - data->actual;
+        d_reference = reference.q - data->reference;
+
+        /* divide by 0, so stay on current frequency as well */
+        if (d_reference == 0) {
+                freq_next = policy->cur;
+                goto out;
+        }
+
+        sensitivity = POWERSAVE_BIAS_MAX -
+                (POWERSAVE_BIAS_MAX * (d_reference - d_actual) / d_reference);
+
+        clamp(sensitivity, 0, POWERSAVE_BIAS_MAX);
+
+        /* this workload is not CPU bound, so choose a lower freq */
+        if (sensitivity < od_tuners->powersave_bias) {
+                if (data->freq_prev == policy->cur)
+                        freq_next = policy->cur;
+
+                if (freq_next > policy->cur)
+                        freq_next = policy->cur;
+                else if (freq_next < policy->cur)
+                        freq_next = policy->min;
+                else {
+                        unsigned int index;
+
+                        cpufreq_frequency_table_target(policy,
+                                od_info->freq_table, policy->cur - 1,
+                                CPUFREQ_RELATION_H, &index);
+                        freq_next = od_info->freq_table[index].frequency;
+                }
+
+                data->freq_prev = freq_next;
+        } else
+                data->freq_prev = 0;
+
+out:
+        data->actual = actual.q;
+        data->reference = reference.q;
+        return freq_next;
+}
+
+static int __init amd_freq_sensitivity_init(void)
+{
+        u64 val;
+
+        if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD)
+                return -ENODEV;
+
+        if (!static_cpu_has(X86_FEATURE_PROC_FEEDBACK))
+                return -ENODEV;
+
+        if (rdmsrl_safe(MSR_AMD64_FREQ_SENSITIVITY_ACTUAL, &val))
+                return -ENODEV;
+
+        if (!(val >> CLASS_CODE_SHIFT))
+                return -ENODEV;
+
+        od_register_powersave_bias_handler(amd_powersave_bias_target,
+                        POWERSAVE_BIAS_DEF);
+        return 0;
+}
+late_initcall(amd_freq_sensitivity_init);
+
+static void __exit amd_freq_sensitivity_exit(void)
+{
+        od_unregister_powersave_bias_handler();
+}
+module_exit(amd_freq_sensitivity_exit);
+
+static const struct x86_cpu_id amd_freq_sensitivity_ids[] = {
+        X86_FEATURE_MATCH(X86_FEATURE_PROC_FEEDBACK),
+        {}
+};
+MODULE_DEVICE_TABLE(x86cpu, amd_freq_sensitivity_ids);
+
+MODULE_AUTHOR("Jacob Shin <jacob.shin@amd.com>");
+MODULE_DESCRIPTION("AMD frequency sensitivity feedback powersave bias for "
+                "the ondemand governor.");
+MODULE_LICENSE("GPL");