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 
25 #include "cpufreq_ondemand.h"
26 
27 #define MSR_AMD64_FREQ_SENSITIVITY_ACTUAL	0xc0010080
28 #define MSR_AMD64_FREQ_SENSITIVITY_REFERENCE	0xc0010081
29 #define CLASS_CODE_SHIFT			56
30 #define POWERSAVE_BIAS_MAX			1000
31 #define POWERSAVE_BIAS_DEF			400
32 
33 struct cpu_data_t {
34 	u64 actual;
35 	u64 reference;
36 	unsigned int freq_prev;
37 };
38 
39 static DEFINE_PER_CPU(struct cpu_data_t, cpu_data);
40 
41 static unsigned int amd_powersave_bias_target(struct cpufreq_policy *policy,
42 					      unsigned int freq_next,
43 					      unsigned int relation)
44 {
45 	int sensitivity;
46 	long d_actual, d_reference;
47 	struct msr actual, reference;
48 	struct cpu_data_t *data = &per_cpu(cpu_data, policy->cpu);
49 	struct policy_dbs_info *policy_dbs = policy->governor_data;
50 	struct dbs_data *od_data = policy_dbs->dbs_data;
51 	struct od_dbs_tuners *od_tuners = od_data->tuners;
52 
53 	if (!policy->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 			index = cpufreq_table_find_index_h(policy,
96 							   policy->cur - 1);
97 			freq_next = policy->freq_table[index].frequency;
98 		}
99 
100 		data->freq_prev = freq_next;
101 	} else
102 		data->freq_prev = 0;
103 
104 out:
105 	data->actual = actual.q;
106 	data->reference = reference.q;
107 	return freq_next;
108 }
109 
110 static int __init amd_freq_sensitivity_init(void)
111 {
112 	u64 val;
113 	struct pci_dev *pcidev;
114 	unsigned int pci_vendor;
115 
116 	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
117 		pci_vendor = PCI_VENDOR_ID_AMD;
118 	else if (boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)
119 		pci_vendor = PCI_VENDOR_ID_HYGON;
120 	else
121 		return -ENODEV;
122 
123 	pcidev = pci_get_device(pci_vendor,
124 			PCI_DEVICE_ID_AMD_KERNCZ_SMBUS, NULL);
125 
126 	if (!pcidev) {
127 		if (!boot_cpu_has(X86_FEATURE_PROC_FEEDBACK))
128 			return -ENODEV;
129 	}
130 
131 	if (rdmsrl_safe(MSR_AMD64_FREQ_SENSITIVITY_ACTUAL, &val))
132 		return -ENODEV;
133 
134 	if (!(val >> CLASS_CODE_SHIFT))
135 		return -ENODEV;
136 
137 	od_register_powersave_bias_handler(amd_powersave_bias_target,
138 			POWERSAVE_BIAS_DEF);
139 	return 0;
140 }
141 late_initcall(amd_freq_sensitivity_init);
142 
143 static void __exit amd_freq_sensitivity_exit(void)
144 {
145 	od_unregister_powersave_bias_handler();
146 }
147 module_exit(amd_freq_sensitivity_exit);
148 
149 static const struct x86_cpu_id amd_freq_sensitivity_ids[] = {
150 	X86_FEATURE_MATCH(X86_FEATURE_PROC_FEEDBACK),
151 	{}
152 };
153 MODULE_DEVICE_TABLE(x86cpu, amd_freq_sensitivity_ids);
154 
155 MODULE_AUTHOR("Jacob Shin <jacob.shin@amd.com>");
156 MODULE_DESCRIPTION("AMD frequency sensitivity feedback powersave bias for "
157 		"the ondemand governor.");
158 MODULE_LICENSE("GPL");
159