1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 *  linux/drivers/devfreq/governor_simpleondemand.c
  4 *
  5 *  Copyright (C) 2011 Samsung Electronics
  6 *	MyungJoo Ham <myungjoo.ham@samsung.com>
  7 */
  8
  9#include <linux/errno.h>
 10#include <linux/module.h>
 11#include <linux/devfreq.h>
 12#include <linux/math64.h>
 13#include "governor.h"
 14
 15/* Default constants for DevFreq-Simple-Ondemand (DFSO) */
 16#define DFSO_UPTHRESHOLD	(90)
 17#define DFSO_DOWNDIFFERENCTIAL	(5)
 18static int devfreq_simple_ondemand_func(struct devfreq *df,
 19					unsigned long *freq)
 20{
 21	int err;
 22	struct devfreq_dev_status *stat;
 23	unsigned long long a, b;
 24	unsigned int dfso_upthreshold = DFSO_UPTHRESHOLD;
 25	unsigned int dfso_downdifferential = DFSO_DOWNDIFFERENCTIAL;
 26	struct devfreq_simple_ondemand_data *data = df->data;
 27
 28	err = devfreq_update_stats(df);
 29	if (err)
 30		return err;
 31
 32	stat = &df->last_status;
 33
 34	if (data) {
 35		if (data->upthreshold)
 36			dfso_upthreshold = data->upthreshold;
 37		if (data->downdifferential)
 38			dfso_downdifferential = data->downdifferential;
 39	}
 40	if (dfso_upthreshold > 100 ||
 41	    dfso_upthreshold < dfso_downdifferential)
 42		return -EINVAL;
 43
 44	/* Assume MAX if it is going to be divided by zero */
 45	if (stat->total_time == 0) {
 46		*freq = DEVFREQ_MAX_FREQ;
 47		return 0;
 48	}
 49
 50	/* Prevent overflow */
 51	if (stat->busy_time >= (1 << 24) || stat->total_time >= (1 << 24)) {
 52		stat->busy_time >>= 7;
 53		stat->total_time >>= 7;
 54	}
 55
 56	/* Set MAX if it's busy enough */
 57	if (stat->busy_time * 100 >
 58	    stat->total_time * dfso_upthreshold) {
 59		*freq = DEVFREQ_MAX_FREQ;
 60		return 0;
 61	}
 62
 63	/* Set MAX if we do not know the initial frequency */
 64	if (stat->current_frequency == 0) {
 65		*freq = DEVFREQ_MAX_FREQ;
 66		return 0;
 67	}
 68
 69	/* Keep the current frequency */
 70	if (stat->busy_time * 100 >
 71	    stat->total_time * (dfso_upthreshold - dfso_downdifferential)) {
 72		*freq = stat->current_frequency;
 73		return 0;
 74	}
 75
 76	/* Set the desired frequency based on the load */
 77	a = stat->busy_time;
 78	a *= stat->current_frequency;
 79	b = div_u64(a, stat->total_time);
 80	b *= 100;
 81	b = div_u64(b, (dfso_upthreshold - dfso_downdifferential / 2));
 82	*freq = (unsigned long) b;
 83
 84	return 0;
 85}
 86
 87static int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
 88				unsigned int event, void *data)
 89{
 90	switch (event) {
 91	case DEVFREQ_GOV_START:
 92		devfreq_monitor_start(devfreq);
 93		break;
 94
 95	case DEVFREQ_GOV_STOP:
 96		devfreq_monitor_stop(devfreq);
 97		break;
 98
 99	case DEVFREQ_GOV_UPDATE_INTERVAL:
100		devfreq_update_interval(devfreq, (unsigned int *)data);
101		break;
102
103	case DEVFREQ_GOV_SUSPEND:
104		devfreq_monitor_suspend(devfreq);
105		break;
106
107	case DEVFREQ_GOV_RESUME:
108		devfreq_monitor_resume(devfreq);
109		break;
110
111	default:
112		break;
113	}
114
115	return 0;
116}
117
118static struct devfreq_governor devfreq_simple_ondemand = {
119	.name = DEVFREQ_GOV_SIMPLE_ONDEMAND,
120	.attrs = DEVFREQ_GOV_ATTR_POLLING_INTERVAL
121		| DEVFREQ_GOV_ATTR_TIMER,
122	.get_target_freq = devfreq_simple_ondemand_func,
123	.event_handler = devfreq_simple_ondemand_handler,
124};
125
126static int __init devfreq_simple_ondemand_init(void)
127{
128	return devfreq_add_governor(&devfreq_simple_ondemand);
129}
130subsys_initcall(devfreq_simple_ondemand_init);
131
132static void __exit devfreq_simple_ondemand_exit(void)
133{
134	int ret;
135
136	ret = devfreq_remove_governor(&devfreq_simple_ondemand);
137	if (ret)
138		pr_err("%s: failed remove governor %d\n", __func__, ret);
139
140	return;
141}
142module_exit(devfreq_simple_ondemand_exit);
143MODULE_LICENSE("GPL");