linux/drivers/cpufreq/amd_freq_sensitivity.c
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   1/*
   2 * amd_freq_sensitivity.c: AMD frequency sensitivity feedback powersave bias
   3 *                         for the ondemand governor.
   4 *
   5 * Copyright (C) 2013 Advanced Micro Devices, Inc.
   6 *
   7 * Author: Jacob Shin <jacob.shin@amd.com>
   8 *
   9 * This program is free software; you can redistribute it and/or modify
  10 * it under the terms of the GNU General Public License version 2 as
  11 * published by the Free Software Foundation.
  12 */
  13
  14#include <linux/kernel.h>
  15#include <linux/module.h>
  16#include <linux/types.h>
  17#include <linux/percpu-defs.h>
  18#include <linux/init.h>
  19#include <linux/mod_devicetable.h>
  20
  21#include <asm/msr.h>
  22#include <asm/cpufeature.h>
  23
  24#include "cpufreq_governor.h"
  25
  26#define MSR_AMD64_FREQ_SENSITIVITY_ACTUAL       0xc0010080
  27#define MSR_AMD64_FREQ_SENSITIVITY_REFERENCE    0xc0010081
  28#define CLASS_CODE_SHIFT                        56
  29#define POWERSAVE_BIAS_MAX                      1000
  30#define POWERSAVE_BIAS_DEF                      400
  31
  32struct cpu_data_t {
  33        u64 actual;
  34        u64 reference;
  35        unsigned int freq_prev;
  36};
  37
  38static DEFINE_PER_CPU(struct cpu_data_t, cpu_data);
  39
  40static unsigned int amd_powersave_bias_target(struct cpufreq_policy *policy,
  41                                              unsigned int freq_next,
  42                                              unsigned int relation)
  43{
  44        int sensitivity;
  45        long d_actual, d_reference;
  46        struct msr actual, reference;
  47        struct cpu_data_t *data = &per_cpu(cpu_data, policy->cpu);
  48        struct dbs_data *od_data = policy->governor_data;
  49        struct od_dbs_tuners *od_tuners = od_data->tuners;
  50        struct od_cpu_dbs_info_s *od_info =
  51                od_data->cdata->get_cpu_dbs_info_s(policy->cpu);
  52
  53        if (!od_info->freq_table)
  54                return freq_next;
  55
  56        rdmsr_on_cpu(policy->cpu, MSR_AMD64_FREQ_SENSITIVITY_ACTUAL,
  57                &actual.l, &actual.h);
  58        rdmsr_on_cpu(policy->cpu, MSR_AMD64_FREQ_SENSITIVITY_REFERENCE,
  59                &reference.l, &reference.h);
  60        actual.h &= 0x00ffffff;
  61        reference.h &= 0x00ffffff;
  62
  63        /* counter wrapped around, so stay on current frequency */
  64        if (actual.q < data->actual || reference.q < data->reference) {
  65                freq_next = policy->cur;
  66                goto out;
  67        }
  68
  69        d_actual = actual.q - data->actual;
  70        d_reference = reference.q - data->reference;
  71
  72        /* divide by 0, so stay on current frequency as well */
  73        if (d_reference == 0) {
  74                freq_next = policy->cur;
  75                goto out;
  76        }
  77
  78        sensitivity = POWERSAVE_BIAS_MAX -
  79                (POWERSAVE_BIAS_MAX * (d_reference - d_actual) / d_reference);
  80
  81        clamp(sensitivity, 0, POWERSAVE_BIAS_MAX);
  82
  83        /* this workload is not CPU bound, so choose a lower freq */
  84        if (sensitivity < od_tuners->powersave_bias) {
  85                if (data->freq_prev == policy->cur)
  86                        freq_next = policy->cur;
  87
  88                if (freq_next > policy->cur)
  89                        freq_next = policy->cur;
  90                else if (freq_next < policy->cur)
  91                        freq_next = policy->min;
  92                else {
  93                        unsigned int index;
  94
  95                        cpufreq_frequency_table_target(policy,
  96                                od_info->freq_table, policy->cur - 1,
  97                                CPUFREQ_RELATION_H, &index);
  98                        freq_next = od_info->freq_table[index].frequency;
  99                }
 100
 101                data->freq_prev = freq_next;
 102        } else
 103                data->freq_prev = 0;
 104
 105out:
 106        data->actual = actual.q;
 107        data->reference = reference.q;
 108        return freq_next;
 109}
 110
 111static int __init amd_freq_sensitivity_init(void)
 112{
 113        u64 val;
 114
 115        if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD)
 116                return -ENODEV;
 117
 118        if (!static_cpu_has(X86_FEATURE_PROC_FEEDBACK))
 119                return -ENODEV;
 120
 121        if (rdmsrl_safe(MSR_AMD64_FREQ_SENSITIVITY_ACTUAL, &val))
 122                return -ENODEV;
 123
 124        if (!(val >> CLASS_CODE_SHIFT))
 125                return -ENODEV;
 126
 127        od_register_powersave_bias_handler(amd_powersave_bias_target,
 128                        POWERSAVE_BIAS_DEF);
 129        return 0;
 130}
 131late_initcall(amd_freq_sensitivity_init);
 132
 133static void __exit amd_freq_sensitivity_exit(void)
 134{
 135        od_unregister_powersave_bias_handler();
 136}
 137module_exit(amd_freq_sensitivity_exit);
 138
 139static const struct x86_cpu_id amd_freq_sensitivity_ids[] = {
 140        X86_FEATURE_MATCH(X86_FEATURE_PROC_FEEDBACK),
 141        {}
 142};
 143MODULE_DEVICE_TABLE(x86cpu, amd_freq_sensitivity_ids);
 144
 145MODULE_AUTHOR("Jacob Shin <jacob.shin@amd.com>");
 146MODULE_DESCRIPTION("AMD frequency sensitivity feedback powersave bias for "
 147                "the ondemand governor.");
 148MODULE_LICENSE("GPL");
 149
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