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
amd_powersave_bias_target(struct cpufreq_policy * policy,unsigned int freq_next,unsigned int relation)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
amd_freq_sensitivity_init(void)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
amd_freq_sensitivity_exit(void)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");
157