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/pci.h>
  18 #include <linux/percpu-defs.h>
  19 #include <linux/init.h>
  20 #include <linux/mod_devicetable.h>
  21
  22 #include <asm/msr.h>
  23 #include <asm/cpufeature.h>
  24 #include <asm/cpu_device_id.h>
  25
  26 #include "cpufreq_ondemand.h"
  27
  28 #define MSR_AMD64_FREQ_SENSITIVITY_ACTUAL       0xc0010080
  29 #define MSR_AMD64_FREQ_SENSITIVITY_REFERENCE    0xc0010081
  30 #define CLASS_CODE_SHIFT                        56
  31 #define POWERSAVE_BIAS_MAX                      1000
  32 #define POWERSAVE_BIAS_DEF                      400
  33
  34 struct cpu_data_t {
  35         u64 actual;
  36         u64 reference;
  37         unsigned int freq_prev;
  38 };
  39
  40 static DEFINE_PER_CPU(struct cpu_data_t, cpu_data);
  41
  42 static unsigned int amd_powersave_bias_target(struct cpufreq_policy *policy,
  43                                               unsigned int freq_next,
  44                                               unsigned int relation)
  45 {
  46         int sensitivity;
  47         long d_actual, d_reference;
  48         struct msr actual, reference;
  49         struct cpu_data_t *data = &per_cpu(cpu_data, policy->cpu);
  50         struct policy_dbs_info *policy_dbs = policy->governor_data;
  51         struct dbs_data *od_data = policy_dbs->dbs_data;
  52         struct od_dbs_tuners *od_tuners = od_data->tuners;
  53
  54         if (!policy->freq_table)
  55                 return freq_next;
  56
  57         rdmsr_on_cpu(policy->cpu, MSR_AMD64_FREQ_SENSITIVITY_ACTUAL,
  58                 &actual.l, &actual.h);
  59         rdmsr_on_cpu(policy->cpu, MSR_AMD64_FREQ_SENSITIVITY_REFERENCE,
  60                 &reference.l, &reference.h);
  61         actual.h &= 0x00ffffff;
  62         reference.h &= 0x00ffffff;
  63
  64         /* counter wrapped around, so stay on current frequency */
  65         if (actual.q < data->actual || reference.q < data->reference) {
  66                 freq_next = policy->cur;
  67                 goto out;
  68         }
  69
  70         d_actual = actual.q - data->actual;
  71         d_reference = reference.q - data->reference;
  72
  73         /* divide by 0, so stay on current frequency as well */
  74         if (d_reference == 0) {
  75                 freq_next = policy->cur;
  76                 goto out;
  77         }
  78
  79         sensitivity = POWERSAVE_BIAS_MAX -
  80                 (POWERSAVE_BIAS_MAX * (d_reference - d_actual) / d_reference);
  81
  82         clamp(sensitivity, 0, POWERSAVE_BIAS_MAX);
  83
  84         /* this workload is not CPU bound, so choose a lower freq */
  85         if (sensitivity < od_tuners->powersave_bias) {
  86                 if (data->freq_prev == policy->cur)
  87                         freq_next = policy->cur;
  88
  89                 if (freq_next > policy->cur)
  90                         freq_next = policy->cur;
  91                 else if (freq_next < policy->cur)
  92                         freq_next = policy->min;
  93                 else {
  94                         unsigned int index;
  95
  96                         index = cpufreq_table_find_index_h(policy,
  97                                                            policy->cur - 1);
  98                         freq_next = policy->freq_table[index].frequency;
  99                 }
 100
 101                 data->freq_prev = freq_next;
 102         } else
 103                 data->freq_prev = 0;
 104
 105 out:
 106         data->actual = actual.q;
 107         data->reference = reference.q;
 108         return freq_next;
 109 }
 110
 111 static int __init amd_freq_sensitivity_init(void)
 112 {
 113         u64 val;
 114         struct pci_dev *pcidev;
 115
 116         if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD)
 117                 return -ENODEV;
 118
 119         pcidev = pci_get_device(PCI_VENDOR_ID_AMD,
 120                         PCI_DEVICE_ID_AMD_KERNCZ_SMBUS, NULL);
 121
 122         if (!pcidev) {
 123                 if (!static_cpu_has(X86_FEATURE_PROC_FEEDBACK))
 124                         return -ENODEV;
 125         } else {
 126                 pci_dev_put(pcidev);
 127         }
 128
 129         if (rdmsrl_safe(MSR_AMD64_FREQ_SENSITIVITY_ACTUAL, &val))
 130                 return -ENODEV;
 131
 132         if (!(val >> CLASS_CODE_SHIFT))
 133                 return -ENODEV;
 134
 135         od_register_powersave_bias_handler(amd_powersave_bias_target,
 136                         POWERSAVE_BIAS_DEF);
 137         return 0;
 138 }
 139 late_initcall(amd_freq_sensitivity_init);
 140
 141 static void __exit amd_freq_sensitivity_exit(void)
 142 {
 143         od_unregister_powersave_bias_handler();
 144 }
 145 module_exit(amd_freq_sensitivity_exit);
 146
 147 static const struct x86_cpu_id amd_freq_sensitivity_ids[] = {
 148         X86_FEATURE_MATCH(X86_FEATURE_PROC_FEEDBACK),
 149         {}
 150 };
 151 MODULE_DEVICE_TABLE(x86cpu, amd_freq_sensitivity_ids);
 152
 153 MODULE_AUTHOR("Jacob Shin <jacob.shin@amd.com>");
 154 MODULE_DESCRIPTION("AMD frequency sensitivity feedback powersave bias for "
 155                 "the ondemand governor.");
 156 MODULE_LICENSE("GPL");