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 
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 
95 static int devfreq_passive_notifier_call(struct notifier_block *nb,
96 				unsigned long event, void *ptr)
97 {
98 	struct devfreq_passive_data *data
99 			= container_of(nb, struct devfreq_passive_data, nb);
100 	struct devfreq *devfreq = (struct devfreq *)data->this;
101 	struct devfreq *parent = (struct devfreq *)data->parent;
102 	struct devfreq_freqs *freqs = (struct devfreq_freqs *)ptr;
103 	unsigned long freq = freqs->new;
104 	int ret = 0;
105 
106 	mutex_lock_nested(&devfreq->lock, SINGLE_DEPTH_NESTING);
107 	switch (event) {
108 	case DEVFREQ_PRECHANGE:
109 		if (parent->previous_freq > freq)
110 			ret = devfreq_update_target(devfreq, freq);
111 
112 		break;
113 	case DEVFREQ_POSTCHANGE:
114 		if (parent->previous_freq < freq)
115 			ret = devfreq_update_target(devfreq, freq);
116 		break;
117 	}
118 	mutex_unlock(&devfreq->lock);
119 
120 	if (ret < 0)
121 		dev_warn(&devfreq->dev,
122 			"failed to update devfreq using passive governor\n");
123 
124 	return NOTIFY_DONE;
125 }
126 
127 static int devfreq_passive_event_handler(struct devfreq *devfreq,
128 				unsigned int event, void *data)
129 {
130 	struct devfreq_passive_data *p_data
131 			= (struct devfreq_passive_data *)devfreq->data;
132 	struct devfreq *parent = (struct devfreq *)p_data->parent;
133 	struct notifier_block *nb = &p_data->nb;
134 	int ret = 0;
135 
136 	if (!parent)
137 		return -EPROBE_DEFER;
138 
139 	switch (event) {
140 	case DEVFREQ_GOV_START:
141 		if (!p_data->this)
142 			p_data->this = devfreq;
143 
144 		nb->notifier_call = devfreq_passive_notifier_call;
145 		ret = devfreq_register_notifier(parent, nb,
146 					DEVFREQ_TRANSITION_NOTIFIER);
147 		break;
148 	case DEVFREQ_GOV_STOP:
149 		WARN_ON(devfreq_unregister_notifier(parent, nb,
150 					DEVFREQ_TRANSITION_NOTIFIER));
151 		break;
152 	default:
153 		break;
154 	}
155 
156 	return ret;
157 }
158 
159 static struct devfreq_governor devfreq_passive = {
160 	.name = DEVFREQ_GOV_PASSIVE,
161 	.flags = DEVFREQ_GOV_FLAG_IMMUTABLE,
162 	.get_target_freq = devfreq_passive_get_target_freq,
163 	.event_handler = devfreq_passive_event_handler,
164 };
165 
166 static int __init devfreq_passive_init(void)
167 {
168 	return devfreq_add_governor(&devfreq_passive);
169 }
170 subsys_initcall(devfreq_passive_init);
171 
172 static void __exit devfreq_passive_exit(void)
173 {
174 	int ret;
175 
176 	ret = devfreq_remove_governor(&devfreq_passive);
177 	if (ret)
178 		pr_err("%s: failed remove governor %d\n", __func__, ret);
179 }
180 module_exit(devfreq_passive_exit);
181 
182 MODULE_AUTHOR("Chanwoo Choi <cw00.choi@samsung.com>");
183 MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
184 MODULE_DESCRIPTION("DEVFREQ Passive governor");
185 MODULE_LICENSE("GPL v2");
186