1 /*
2  * linux/drivers/devfreq/governor_passive.c
3  *
4  * Copyright (C) 2016 Samsung Electronics
5  * Author: Chanwoo Choi <cw00.choi@samsung.com>
6  * Author: MyungJoo Ham <myungjoo.ham@samsung.com>
7  *
8  * This program is free software; you can redistribute it and/or modify
9  * it under the terms of the GNU General Public License version 2 as
10  * published by the Free Software Foundation.
11  */
12 
13 #include <linux/module.h>
14 #include <linux/device.h>
15 #include <linux/devfreq.h>
16 #include "governor.h"
17 
18 static int devfreq_passive_get_target_freq(struct devfreq *devfreq,
19 					unsigned long *freq)
20 {
21 	struct devfreq_passive_data *p_data
22 			= (struct devfreq_passive_data *)devfreq->data;
23 	struct devfreq *parent_devfreq = (struct devfreq *)p_data->parent;
24 	unsigned long child_freq = ULONG_MAX;
25 	struct dev_pm_opp *opp;
26 	int i, count, ret = 0;
27 
28 	/*
29 	 * If the devfreq device with passive governor has the specific method
30 	 * to determine the next frequency, should use the get_target_freq()
31 	 * of struct devfreq_passive_data.
32 	 */
33 	if (p_data->get_target_freq) {
34 		ret = p_data->get_target_freq(devfreq, freq);
35 		goto out;
36 	}
37 
38 	/*
39 	 * If the parent and passive devfreq device uses the OPP table,
40 	 * get the next frequency by using the OPP table.
41 	 */
42 
43 	/*
44 	 * - parent devfreq device uses the governors except for passive.
45 	 * - passive devfreq device uses the passive governor.
46 	 *
47 	 * Each devfreq has the OPP table. After deciding the new frequency
48 	 * from the governor of parent devfreq device, the passive governor
49 	 * need to get the index of new frequency on OPP table of parent
50 	 * device. And then the index is used for getting the suitable
51 	 * new frequency for passive devfreq device.
52 	 */
53 	if (!devfreq->profile || !devfreq->profile->freq_table
54 		|| devfreq->profile->max_state <= 0)
55 		return -EINVAL;
56 
57 	/*
58 	 * The passive governor have to get the correct frequency from OPP
59 	 * list of parent device. Because in this case, *freq is temporary
60 	 * value which is decided by ondemand governor.
61 	 */
62 	opp = devfreq_recommended_opp(parent_devfreq->dev.parent, freq, 0);
63 	if (IS_ERR(opp)) {
64 		ret = PTR_ERR(opp);
65 		goto out;
66 	}
67 
68 	dev_pm_opp_put(opp);
69 
70 	/*
71 	 * Get the OPP table's index of decided freqeuncy by governor
72 	 * of parent device.
73 	 */
74 	for (i = 0; i < parent_devfreq->profile->max_state; i++)
75 		if (parent_devfreq->profile->freq_table[i] == *freq)
76 			break;
77 
78 	if (i == parent_devfreq->profile->max_state) {
79 		ret = -EINVAL;
80 		goto out;
81 	}
82 
83 	/* Get the suitable frequency by using index of parent device. */
84 	if (i < devfreq->profile->max_state) {
85 		child_freq = devfreq->profile->freq_table[i];
86 	} else {
87 		count = devfreq->profile->max_state;
88 		child_freq = devfreq->profile->freq_table[count - 1];
89 	}
90 
91 	/* Return the suitable frequency for passive device. */
92 	*freq = child_freq;
93 
94 out:
95 	return ret;
96 }
97 
98 static int update_devfreq_passive(struct devfreq *devfreq, unsigned long freq)
99 {
100 	int ret;
101 
102 	if (!devfreq->governor)
103 		return -EINVAL;
104 
105 	mutex_lock_nested(&devfreq->lock, SINGLE_DEPTH_NESTING);
106 
107 	ret = devfreq->governor->get_target_freq(devfreq, &freq);
108 	if (ret < 0)
109 		goto out;
110 
111 	ret = devfreq->profile->target(devfreq->dev.parent, &freq, 0);
112 	if (ret < 0)
113 		goto out;
114 
115 	if (devfreq->profile->freq_table
116 		&& (devfreq_update_status(devfreq, freq)))
117 		dev_err(&devfreq->dev,
118 			"Couldn't update frequency transition information.\n");
119 
120 	devfreq->previous_freq = freq;
121 
122 out:
123 	mutex_unlock(&devfreq->lock);
124 
125 	return 0;
126 }
127 
128 static int devfreq_passive_notifier_call(struct notifier_block *nb,
129 				unsigned long event, void *ptr)
130 {
131 	struct devfreq_passive_data *data
132 			= container_of(nb, struct devfreq_passive_data, nb);
133 	struct devfreq *devfreq = (struct devfreq *)data->this;
134 	struct devfreq *parent = (struct devfreq *)data->parent;
135 	struct devfreq_freqs *freqs = (struct devfreq_freqs *)ptr;
136 	unsigned long freq = freqs->new;
137 
138 	switch (event) {
139 	case DEVFREQ_PRECHANGE:
140 		if (parent->previous_freq > freq)
141 			update_devfreq_passive(devfreq, freq);
142 		break;
143 	case DEVFREQ_POSTCHANGE:
144 		if (parent->previous_freq < freq)
145 			update_devfreq_passive(devfreq, freq);
146 		break;
147 	}
148 
149 	return NOTIFY_DONE;
150 }
151 
152 static int devfreq_passive_event_handler(struct devfreq *devfreq,
153 				unsigned int event, void *data)
154 {
155 	struct device *dev = devfreq->dev.parent;
156 	struct devfreq_passive_data *p_data
157 			= (struct devfreq_passive_data *)devfreq->data;
158 	struct devfreq *parent = (struct devfreq *)p_data->parent;
159 	struct notifier_block *nb = &p_data->nb;
160 	int ret = 0;
161 
162 	if (!parent)
163 		return -EPROBE_DEFER;
164 
165 	switch (event) {
166 	case DEVFREQ_GOV_START:
167 		if (!p_data->this)
168 			p_data->this = devfreq;
169 
170 		nb->notifier_call = devfreq_passive_notifier_call;
171 		ret = devm_devfreq_register_notifier(dev, parent, nb,
172 					DEVFREQ_TRANSITION_NOTIFIER);
173 		break;
174 	case DEVFREQ_GOV_STOP:
175 		devm_devfreq_unregister_notifier(dev, parent, nb,
176 					DEVFREQ_TRANSITION_NOTIFIER);
177 		break;
178 	default:
179 		break;
180 	}
181 
182 	return ret;
183 }
184 
185 static struct devfreq_governor devfreq_passive = {
186 	.name = DEVFREQ_GOV_PASSIVE,
187 	.immutable = 1,
188 	.get_target_freq = devfreq_passive_get_target_freq,
189 	.event_handler = devfreq_passive_event_handler,
190 };
191 
192 static int __init devfreq_passive_init(void)
193 {
194 	return devfreq_add_governor(&devfreq_passive);
195 }
196 subsys_initcall(devfreq_passive_init);
197 
198 static void __exit devfreq_passive_exit(void)
199 {
200 	int ret;
201 
202 	ret = devfreq_remove_governor(&devfreq_passive);
203 	if (ret)
204 		pr_err("%s: failed remove governor %d\n", __func__, ret);
205 }
206 module_exit(devfreq_passive_exit);
207 
208 MODULE_AUTHOR("Chanwoo Choi <cw00.choi@samsung.com>");
209 MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
210 MODULE_DESCRIPTION("DEVFREQ Passive governor");
211 MODULE_LICENSE("GPL v2");
212