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
 18static 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
 94out:
 95	return ret;
 96}
 97
 98static 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
122out:
123	mutex_unlock(&devfreq->lock);
124
125	return 0;
126}
127
128static 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
152static 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
185static 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
192static int __init devfreq_passive_init(void)
193{
194	return devfreq_add_governor(&devfreq_passive);
195}
196subsys_initcall(devfreq_passive_init);
197
198static 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}
206module_exit(devfreq_passive_exit);
207
208MODULE_AUTHOR("Chanwoo Choi <cw00.choi@samsung.com>");
209MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
210MODULE_DESCRIPTION("DEVFREQ Passive governor");
211MODULE_LICENSE("GPL v2");