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
32struct cpu_data_t {
33	u64 actual;
34	u64 reference;
35	unsigned int freq_prev;
36};
37
38static DEFINE_PER_CPU(struct cpu_data_t, cpu_data);
39
40static 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
105out:
106	data->actual = actual.q;
107	data->reference = reference.q;
108	return freq_next;
109}
110
111static 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}
131late_initcall(amd_freq_sensitivity_init);
132
133static void __exit amd_freq_sensitivity_exit(void)
134{
135	od_unregister_powersave_bias_handler();
136}
137module_exit(amd_freq_sensitivity_exit);
138
139static const struct x86_cpu_id amd_freq_sensitivity_ids[] = {
140	X86_FEATURE_MATCH(X86_FEATURE_PROC_FEEDBACK),
141	{}
142};
143MODULE_DEVICE_TABLE(x86cpu, amd_freq_sensitivity_ids);
144
145MODULE_AUTHOR("Jacob Shin <jacob.shin@amd.com>");
146MODULE_DESCRIPTION("AMD frequency sensitivity feedback powersave bias for "
147		"the ondemand governor.");
148MODULE_LICENSE("GPL");
149