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)
18 static 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 
87 static 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_INTERVAL:
100 		devfreq_interval_update(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 
118 static 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 
124 static int __init devfreq_simple_ondemand_init(void)
125 {
126 	return devfreq_add_governor(&devfreq_simple_ondemand);
127 }
128 subsys_initcall(devfreq_simple_ondemand_init);
129 
130 static 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 }
140 module_exit(devfreq_simple_ondemand_exit);
141 MODULE_LICENSE("GPL");
142