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
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
amd_powersave_bias_target(struct cpufreq_policy * policy,unsigned int freq_next,unsigned int relation)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 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
105 out:
106 data->actual = actual.q;
107 data->reference = reference.q;
108 return freq_next;
109 }
110
amd_freq_sensitivity_init(void)111 static 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 }
131 late_initcall(amd_freq_sensitivity_init);
132
amd_freq_sensitivity_exit(void)133 static void __exit amd_freq_sensitivity_exit(void)
134 {
135 od_unregister_powersave_bias_handler();
136 }
137 module_exit(amd_freq_sensitivity_exit);
138
139 static const struct x86_cpu_id amd_freq_sensitivity_ids[] = {
140 X86_FEATURE_MATCH(X86_FEATURE_PROC_FEEDBACK),
141 {}
142 };
143 MODULE_DEVICE_TABLE(x86cpu, amd_freq_sensitivity_ids);
144
145 MODULE_AUTHOR("Jacob Shin <jacob.shin@amd.com>");
146 MODULE_DESCRIPTION("AMD frequency sensitivity feedback powersave bias for "
147 "the ondemand governor.");
148 MODULE_LICENSE("GPL");
149