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"); 147