1 /*
2  *  linux/drivers/devfreq/governor_simpleondemand.c
3  *
4  *  Copyright (C) 2011 Samsung Electronics
5  *	MyungJoo Ham <myungjoo.ham@samsung.com>
6  *
7  * This program is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License version 2 as
9  * published by the Free Software Foundation.
10  */
11 
12 #include <linux/errno.h>
13 #include <linux/module.h>
14 #include <linux/devfreq.h>
15 #include <linux/math64.h>
16 #include "governor.h"
17 
18 /* Default constants for DevFreq-Simple-Ondemand (DFSO) */
19 #define DFSO_UPTHRESHOLD	(90)
20 #define DFSO_DOWNDIFFERENCTIAL	(5)
21 static int devfreq_simple_ondemand_func(struct devfreq *df,
22 					unsigned long *freq)
23 {
24 	int err;
25 	struct devfreq_dev_status *stat;
26 	unsigned long long a, b;
27 	unsigned int dfso_upthreshold = DFSO_UPTHRESHOLD;
28 	unsigned int dfso_downdifferential = DFSO_DOWNDIFFERENCTIAL;
29 	struct devfreq_simple_ondemand_data *data = df->data;
30 	unsigned long max = (df->max_freq) ? df->max_freq : UINT_MAX;
31 
32 	err = devfreq_update_stats(df);
33 	if (err)
34 		return err;
35 
36 	stat = &df->last_status;
37 
38 	if (data) {
39 		if (data->upthreshold)
40 			dfso_upthreshold = data->upthreshold;
41 		if (data->downdifferential)
42 			dfso_downdifferential = data->downdifferential;
43 	}
44 	if (dfso_upthreshold > 100 ||
45 	    dfso_upthreshold < dfso_downdifferential)
46 		return -EINVAL;
47 
48 	/* Assume MAX if it is going to be divided by zero */
49 	if (stat->total_time == 0) {
50 		*freq = max;
51 		return 0;
52 	}
53 
54 	/* Prevent overflow */
55 	if (stat->busy_time >= (1 << 24) || stat->total_time >= (1 << 24)) {
56 		stat->busy_time >>= 7;
57 		stat->total_time >>= 7;
58 	}
59 
60 	/* Set MAX if it's busy enough */
61 	if (stat->busy_time * 100 >
62 	    stat->total_time * dfso_upthreshold) {
63 		*freq = max;
64 		return 0;
65 	}
66 
67 	/* Set MAX if we do not know the initial frequency */
68 	if (stat->current_frequency == 0) {
69 		*freq = max;
70 		return 0;
71 	}
72 
73 	/* Keep the current frequency */
74 	if (stat->busy_time * 100 >
75 	    stat->total_time * (dfso_upthreshold - dfso_downdifferential)) {
76 		*freq = stat->current_frequency;
77 		return 0;
78 	}
79 
80 	/* Set the desired frequency based on the load */
81 	a = stat->busy_time;
82 	a *= stat->current_frequency;
83 	b = div_u64(a, stat->total_time);
84 	b *= 100;
85 	b = div_u64(b, (dfso_upthreshold - dfso_downdifferential / 2));
86 	*freq = (unsigned long) b;
87 
88 	if (df->min_freq && *freq < df->min_freq)
89 		*freq = df->min_freq;
90 	if (df->max_freq && *freq > df->max_freq)
91 		*freq = df->max_freq;
92 
93 	return 0;
94 }
95 
96 static int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
97 				unsigned int event, void *data)
98 {
99 	switch (event) {
100 	case DEVFREQ_GOV_START:
101 		devfreq_monitor_start(devfreq);
102 		break;
103 
104 	case DEVFREQ_GOV_STOP:
105 		devfreq_monitor_stop(devfreq);
106 		break;
107 
108 	case DEVFREQ_GOV_INTERVAL:
109 		devfreq_interval_update(devfreq, (unsigned int *)data);
110 		break;
111 
112 	case DEVFREQ_GOV_SUSPEND:
113 		devfreq_monitor_suspend(devfreq);
114 		break;
115 
116 	case DEVFREQ_GOV_RESUME:
117 		devfreq_monitor_resume(devfreq);
118 		break;
119 
120 	default:
121 		break;
122 	}
123 
124 	return 0;
125 }
126 
127 static struct devfreq_governor devfreq_simple_ondemand = {
128 	.name = "simple_ondemand",
129 	.get_target_freq = devfreq_simple_ondemand_func,
130 	.event_handler = devfreq_simple_ondemand_handler,
131 };
132 
133 static int __init devfreq_simple_ondemand_init(void)
134 {
135 	return devfreq_add_governor(&devfreq_simple_ondemand);
136 }
137 subsys_initcall(devfreq_simple_ondemand_init);
138 
139 static void __exit devfreq_simple_ondemand_exit(void)
140 {
141 	int ret;
142 
143 	ret = devfreq_remove_governor(&devfreq_simple_ondemand);
144 	if (ret)
145 		pr_err("%s: failed remove governor %d\n", __func__, ret);
146 
147 	return;
148 }
149 module_exit(devfreq_simple_ondemand_exit);
150 MODULE_LICENSE("GPL");
151