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	.get_target_freq = devfreq_simple_ondemand_func,
121	.event_handler = devfreq_simple_ondemand_handler,
122};
123
124static int __init devfreq_simple_ondemand_init(void)
125{
126	return devfreq_add_governor(&devfreq_simple_ondemand);
127}
128subsys_initcall(devfreq_simple_ondemand_init);
129
130static void __exit devfreq_simple_ondemand_exit(void)
131{
132	int ret;
133
134	ret = devfreq_remove_governor(&devfreq_simple_ondemand);
135	if (ret)
136		pr_err("%s: failed remove governor %d\n", __func__, ret);
137
138	return;
139}
140module_exit(devfreq_simple_ondemand_exit);
141MODULE_LICENSE("GPL");
142