1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * linux/drivers/devfreq/governor_passive.c
4 *
5 * Copyright (C) 2016 Samsung Electronics
6 * Author: Chanwoo Choi <cw00.choi@samsung.com>
7 * Author: MyungJoo Ham <myungjoo.ham@samsung.com>
8 */
9
10 #include <linux/module.h>
11 #include <linux/device.h>
12 #include <linux/devfreq.h>
13 #include "governor.h"
14
devfreq_passive_get_target_freq(struct devfreq * devfreq,unsigned long * freq)15 static int devfreq_passive_get_target_freq(struct devfreq *devfreq,
16 unsigned long *freq)
17 {
18 struct devfreq_passive_data *p_data
19 = (struct devfreq_passive_data *)devfreq->data;
20 struct devfreq *parent_devfreq = (struct devfreq *)p_data->parent;
21 unsigned long child_freq = ULONG_MAX;
22 struct dev_pm_opp *opp;
23 int i, count, ret = 0;
24
25 /*
26 * If the devfreq device with passive governor has the specific method
27 * to determine the next frequency, should use the get_target_freq()
28 * of struct devfreq_passive_data.
29 */
30 if (p_data->get_target_freq) {
31 ret = p_data->get_target_freq(devfreq, freq);
32 goto out;
33 }
34
35 /*
36 * If the parent and passive devfreq device uses the OPP table,
37 * get the next frequency by using the OPP table.
38 */
39
40 /*
41 * - parent devfreq device uses the governors except for passive.
42 * - passive devfreq device uses the passive governor.
43 *
44 * Each devfreq has the OPP table. After deciding the new frequency
45 * from the governor of parent devfreq device, the passive governor
46 * need to get the index of new frequency on OPP table of parent
47 * device. And then the index is used for getting the suitable
48 * new frequency for passive devfreq device.
49 */
50 if (!devfreq->profile || !devfreq->profile->freq_table
51 || devfreq->profile->max_state <= 0)
52 return -EINVAL;
53
54 /*
55 * The passive governor have to get the correct frequency from OPP
56 * list of parent device. Because in this case, *freq is temporary
57 * value which is decided by ondemand governor.
58 */
59 opp = devfreq_recommended_opp(parent_devfreq->dev.parent, freq, 0);
60 if (IS_ERR(opp)) {
61 ret = PTR_ERR(opp);
62 goto out;
63 }
64
65 dev_pm_opp_put(opp);
66
67 /*
68 * Get the OPP table's index of decided freqeuncy by governor
69 * of parent device.
70 */
71 for (i = 0; i < parent_devfreq->profile->max_state; i++)
72 if (parent_devfreq->profile->freq_table[i] == *freq)
73 break;
74
75 if (i == parent_devfreq->profile->max_state) {
76 ret = -EINVAL;
77 goto out;
78 }
79
80 /* Get the suitable frequency by using index of parent device. */
81 if (i < devfreq->profile->max_state) {
82 child_freq = devfreq->profile->freq_table[i];
83 } else {
84 count = devfreq->profile->max_state;
85 child_freq = devfreq->profile->freq_table[count - 1];
86 }
87
88 /* Return the suitable frequency for passive device. */
89 *freq = child_freq;
90
91 out:
92 return ret;
93 }
94
update_devfreq_passive(struct devfreq * devfreq,unsigned long freq)95 static int update_devfreq_passive(struct devfreq *devfreq, unsigned long freq)
96 {
97 int ret;
98
99 if (!devfreq->governor)
100 return -EINVAL;
101
102 mutex_lock_nested(&devfreq->lock, SINGLE_DEPTH_NESTING);
103
104 ret = devfreq->governor->get_target_freq(devfreq, &freq);
105 if (ret < 0)
106 goto out;
107
108 ret = devfreq->profile->target(devfreq->dev.parent, &freq, 0);
109 if (ret < 0)
110 goto out;
111
112 if (devfreq->profile->freq_table
113 && (devfreq_update_status(devfreq, freq)))
114 dev_err(&devfreq->dev,
115 "Couldn't update frequency transition information.\n");
116
117 devfreq->previous_freq = freq;
118
119 out:
120 mutex_unlock(&devfreq->lock);
121
122 return 0;
123 }
124
devfreq_passive_notifier_call(struct notifier_block * nb,unsigned long event,void * ptr)125 static int devfreq_passive_notifier_call(struct notifier_block *nb,
126 unsigned long event, void *ptr)
127 {
128 struct devfreq_passive_data *data
129 = container_of(nb, struct devfreq_passive_data, nb);
130 struct devfreq *devfreq = (struct devfreq *)data->this;
131 struct devfreq *parent = (struct devfreq *)data->parent;
132 struct devfreq_freqs *freqs = (struct devfreq_freqs *)ptr;
133 unsigned long freq = freqs->new;
134
135 switch (event) {
136 case DEVFREQ_PRECHANGE:
137 if (parent->previous_freq > freq)
138 update_devfreq_passive(devfreq, freq);
139 break;
140 case DEVFREQ_POSTCHANGE:
141 if (parent->previous_freq < freq)
142 update_devfreq_passive(devfreq, freq);
143 break;
144 }
145
146 return NOTIFY_DONE;
147 }
148
devfreq_passive_event_handler(struct devfreq * devfreq,unsigned int event,void * data)149 static int devfreq_passive_event_handler(struct devfreq *devfreq,
150 unsigned int event, void *data)
151 {
152 struct devfreq_passive_data *p_data
153 = (struct devfreq_passive_data *)devfreq->data;
154 struct devfreq *parent = (struct devfreq *)p_data->parent;
155 struct notifier_block *nb = &p_data->nb;
156 int ret = 0;
157
158 if (!parent)
159 return -EPROBE_DEFER;
160
161 switch (event) {
162 case DEVFREQ_GOV_START:
163 if (!p_data->this)
164 p_data->this = devfreq;
165
166 nb->notifier_call = devfreq_passive_notifier_call;
167 ret = devfreq_register_notifier(parent, nb,
168 DEVFREQ_TRANSITION_NOTIFIER);
169 break;
170 case DEVFREQ_GOV_STOP:
171 WARN_ON(devfreq_unregister_notifier(parent, nb,
172 DEVFREQ_TRANSITION_NOTIFIER));
173 break;
174 default:
175 break;
176 }
177
178 return ret;
179 }
180
181 static struct devfreq_governor devfreq_passive = {
182 .name = DEVFREQ_GOV_PASSIVE,
183 .immutable = 1,
184 .get_target_freq = devfreq_passive_get_target_freq,
185 .event_handler = devfreq_passive_event_handler,
186 };
187
devfreq_passive_init(void)188 static int __init devfreq_passive_init(void)
189 {
190 return devfreq_add_governor(&devfreq_passive);
191 }
192 subsys_initcall(devfreq_passive_init);
193
devfreq_passive_exit(void)194 static void __exit devfreq_passive_exit(void)
195 {
196 int ret;
197
198 ret = devfreq_remove_governor(&devfreq_passive);
199 if (ret)
200 pr_err("%s: failed remove governor %d\n", __func__, ret);
201 }
202 module_exit(devfreq_passive_exit);
203
204 MODULE_AUTHOR("Chanwoo Choi <cw00.choi@samsung.com>");
205 MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
206 MODULE_DESCRIPTION("DEVFREQ Passive governor");
207 MODULE_LICENSE("GPL v2");
208