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
 15static 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
 91out:
 92	return ret;
 93}
 94
 95static 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
119out:
120	mutex_unlock(&devfreq->lock);
121
122	return 0;
123}
124
125static 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
149static 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
181static 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
188static int __init devfreq_passive_init(void)
189{
190	return devfreq_add_governor(&devfreq_passive);
191}
192subsys_initcall(devfreq_passive_init);
193
194static 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}
202module_exit(devfreq_passive_exit);
203
204MODULE_AUTHOR("Chanwoo Choi <cw00.choi@samsung.com>");
205MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
206MODULE_DESCRIPTION("DEVFREQ Passive governor");
207MODULE_LICENSE("GPL v2");