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 	struct od_policy_dbs_info *od_info = to_dbs_info(policy_dbs);
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 
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 
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