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, *p_opp;
 23	int i, count;
 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		return p_data->get_target_freq(devfreq, freq);
 32
 33	/*
 34	 * If the parent and passive devfreq device uses the OPP table,
 35	 * get the next frequency by using the OPP table.
 36	 */
 37
 38	/*
 39	 * - parent devfreq device uses the governors except for passive.
 40	 * - passive devfreq device uses the passive governor.
 41	 *
 42	 * Each devfreq has the OPP table. After deciding the new frequency
 43	 * from the governor of parent devfreq device, the passive governor
 44	 * need to get the index of new frequency on OPP table of parent
 45	 * device. And then the index is used for getting the suitable
 46	 * new frequency for passive devfreq device.
 47	 */
 48	if (!devfreq->profile || !devfreq->profile->freq_table
 49		|| devfreq->profile->max_state <= 0)
 50		return -EINVAL;
 51
 52	/*
 53	 * The passive governor have to get the correct frequency from OPP
 54	 * list of parent device. Because in this case, *freq is temporary
 55	 * value which is decided by ondemand governor.
 56	 */
 57	if (devfreq->opp_table && parent_devfreq->opp_table) {
 58		p_opp = devfreq_recommended_opp(parent_devfreq->dev.parent,
 59						freq, 0);
 60		if (IS_ERR(p_opp))
 61			return PTR_ERR(p_opp);
 62
 63		opp = dev_pm_opp_xlate_required_opp(parent_devfreq->opp_table,
 64						    devfreq->opp_table, p_opp);
 65		dev_pm_opp_put(p_opp);
 66
 67		if (IS_ERR(opp))
 68			goto no_required_opp;
 69
 70		*freq = dev_pm_opp_get_freq(opp);
 71		dev_pm_opp_put(opp);
 72
 73		return 0;
 74	}
 75
 76no_required_opp:
 77	/*
 78	 * Get the OPP table's index of decided frequency by governor
 79	 * of parent device.
 80	 */
 81	for (i = 0; i < parent_devfreq->profile->max_state; i++)
 82		if (parent_devfreq->profile->freq_table[i] == *freq)
 83			break;
 84
 85	if (i == parent_devfreq->profile->max_state)
 86		return -EINVAL;
 87
 88	/* Get the suitable frequency by using index of parent device. */
 89	if (i < devfreq->profile->max_state) {
 90		child_freq = devfreq->profile->freq_table[i];
 91	} else {
 92		count = devfreq->profile->max_state;
 93		child_freq = devfreq->profile->freq_table[count - 1];
 94	}
 95
 96	/* Return the suitable frequency for passive device. */
 97	*freq = child_freq;
 98
 99	return 0;
100}
101
102static int devfreq_passive_notifier_call(struct notifier_block *nb,
103				unsigned long event, void *ptr)
104{
105	struct devfreq_passive_data *data
106			= container_of(nb, struct devfreq_passive_data, nb);
107	struct devfreq *devfreq = (struct devfreq *)data->this;
108	struct devfreq *parent = (struct devfreq *)data->parent;
109	struct devfreq_freqs *freqs = (struct devfreq_freqs *)ptr;
110	unsigned long freq = freqs->new;
111	int ret = 0;
112
113	mutex_lock_nested(&devfreq->lock, SINGLE_DEPTH_NESTING);
114	switch (event) {
115	case DEVFREQ_PRECHANGE:
116		if (parent->previous_freq > freq)
117			ret = devfreq_update_target(devfreq, freq);
118
119		break;
120	case DEVFREQ_POSTCHANGE:
121		if (parent->previous_freq < freq)
122			ret = devfreq_update_target(devfreq, freq);
123		break;
124	}
125	mutex_unlock(&devfreq->lock);
126
127	if (ret < 0)
128		dev_warn(&devfreq->dev,
129			"failed to update devfreq using passive governor\n");
130
131	return NOTIFY_DONE;
132}
133
134static int devfreq_passive_event_handler(struct devfreq *devfreq,
135				unsigned int event, void *data)
136{
137	struct devfreq_passive_data *p_data
138			= (struct devfreq_passive_data *)devfreq->data;
139	struct devfreq *parent = (struct devfreq *)p_data->parent;
140	struct notifier_block *nb = &p_data->nb;
141	int ret = 0;
142
143	if (!parent)
144		return -EPROBE_DEFER;
145
146	switch (event) {
147	case DEVFREQ_GOV_START:
148		if (!p_data->this)
149			p_data->this = devfreq;
150
151		nb->notifier_call = devfreq_passive_notifier_call;
152		ret = devfreq_register_notifier(parent, nb,
153					DEVFREQ_TRANSITION_NOTIFIER);
154		break;
155	case DEVFREQ_GOV_STOP:
156		WARN_ON(devfreq_unregister_notifier(parent, nb,
157					DEVFREQ_TRANSITION_NOTIFIER));
158		break;
159	default:
160		break;
161	}
162
163	return ret;
164}
165
166static struct devfreq_governor devfreq_passive = {
167	.name = DEVFREQ_GOV_PASSIVE,
168	.flags = DEVFREQ_GOV_FLAG_IMMUTABLE,
169	.get_target_freq = devfreq_passive_get_target_freq,
170	.event_handler = devfreq_passive_event_handler,
171};
172
173static int __init devfreq_passive_init(void)
174{
175	return devfreq_add_governor(&devfreq_passive);
176}
177subsys_initcall(devfreq_passive_init);
178
179static void __exit devfreq_passive_exit(void)
180{
181	int ret;
182
183	ret = devfreq_remove_governor(&devfreq_passive);
184	if (ret)
185		pr_err("%s: failed remove governor %d\n", __func__, ret);
186}
187module_exit(devfreq_passive_exit);
188
189MODULE_AUTHOR("Chanwoo Choi <cw00.choi@samsung.com>");
190MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
191MODULE_DESCRIPTION("DEVFREQ Passive governor");
192MODULE_LICENSE("GPL v2");