drivers/cpufreq/amd_freq_sensitivity.c

   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_ondemand.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
  32 struct cpu_data_t {
  33         u64 actual;
  34         u64 reference;
  35         unsigned int freq_prev;
  36 };
  37
  38 static DEFINE_PER_CPU(struct cpu_data_t, cpu_data);
  39
  40 static 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 policy_dbs_info *policy_dbs = policy->governor_data;
  49         struct dbs_data *od_data = policy_dbs->dbs_data;
  50         struct od_dbs_tuners *od_tuners = od_data->tuners;
  51
  52         if (!policy->freq_table)
  53                 return freq_next;
  54
  55         rdmsr_on_cpu(policy->cpu, MSR_AMD64_FREQ_SENSITIVITY_ACTUAL,
  56                 &actual.l, &actual.h);
  57         rdmsr_on_cpu(policy->cpu, MSR_AMD64_FREQ_SENSITIVITY_REFERENCE,
  58                 &reference.l, &reference.h);
  59         actual.h &= 0x00ffffff;
  60         reference.h &= 0x00ffffff;
  61
  62         /* counter wrapped around, so stay on current frequency */
  63         if (actual.q < data->actual || reference.q < data->reference) {
  64                 freq_next = policy->cur;
  65                 goto out;
  66         }
  67
  68         d_actual = actual.q - data->actual;
  69         d_reference = reference.q - data->reference;
  70
  71         /* divide by 0, so stay on current frequency as well */
  72         if (d_reference == 0) {
  73                 freq_next = policy->cur;
  74                 goto out;
  75         }
  76
  77         sensitivity = POWERSAVE_BIAS_MAX -
  78                 (POWERSAVE_BIAS_MAX * (d_reference - d_actual) / d_reference);
  79
  80         clamp(sensitivity, 0, POWERSAVE_BIAS_MAX);
  81
  82         /* this workload is not CPU bound, so choose a lower freq */
  83         if (sensitivity < od_tuners->powersave_bias) {
  84                 if (data->freq_prev == policy->cur)
  85                         freq_next = policy->cur;
  86
  87                 if (freq_next > policy->cur)
  88                         freq_next = policy->cur;
  89                 else if (freq_next < policy->cur)
  90                         freq_next = policy->min;
  91                 else {
  92                         unsigned int index;
  93
  94                         index = cpufreq_table_find_index_h(policy,
  95                                                            policy->cur - 1);
  96                         freq_next = policy->freq_table[index].frequency;
  97                 }
  98
  99                 data->freq_prev = freq_next;
 100         } else
 101                 data->freq_prev = 0;
 102
 103 out:
 104         data->actual = actual.q;
 105         data->reference = reference.q;
 106         return freq_next;
 107 }
 108
 109 static int __init amd_freq_sensitivity_init(void)
 110 {
 111         u64 val;
 112
 113         if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD)
 114                 return -ENODEV;
 115
 116         if (!static_cpu_has(X86_FEATURE_PROC_FEEDBACK))
 117                 return -ENODEV;
 118
 119         if (rdmsrl_safe(MSR_AMD64_FREQ_SENSITIVITY_ACTUAL, &val))
 120                 return -ENODEV;
 121
 122         if (!(val >> CLASS_CODE_SHIFT))
 123                 return -ENODEV;
 124
 125         od_register_powersave_bias_handler(amd_powersave_bias_target,
 126                         POWERSAVE_BIAS_DEF);
 127         return 0;
 128 }
 129 late_initcall(amd_freq_sensitivity_init);
 130
 131 static void __exit amd_freq_sensitivity_exit(void)
 132 {
 133         od_unregister_powersave_bias_handler();
 134 }
 135 module_exit(amd_freq_sensitivity_exit);
 136
 137 static const struct x86_cpu_id amd_freq_sensitivity_ids[] = {
 138         X86_FEATURE_MATCH(X86_FEATURE_PROC_FEEDBACK),
 139         {}
 140 };
 141 MODULE_DEVICE_TABLE(x86cpu, amd_freq_sensitivity_ids);
 142
 143 MODULE_AUTHOR("Jacob Shin <jacob.shin@amd.com>");
 144 MODULE_DESCRIPTION("AMD frequency sensitivity feedback powersave bias for "
 145                 "the ondemand governor.");
 146 MODULE_LICENSE("GPL");