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 
31 	err = devfreq_update_stats(df);
32 	if (err)
33 		return err;
34 
35 	stat = &df->last_status;
36 
37 	if (data) {
38 		if (data->upthreshold)
39 			dfso_upthreshold = data->upthreshold;
40 		if (data->downdifferential)
41 			dfso_downdifferential = data->downdifferential;
42 	}
43 	if (dfso_upthreshold > 100 ||
44 	    dfso_upthreshold < dfso_downdifferential)
45 		return -EINVAL;
46 
47 	/* Assume MAX if it is going to be divided by zero */
48 	if (stat->total_time == 0) {
49 		*freq = DEVFREQ_MAX_FREQ;
50 		return 0;
51 	}
52 
53 	/* Prevent overflow */
54 	if (stat->busy_time >= (1 << 24) || stat->total_time >= (1 << 24)) {
55 		stat->busy_time >>= 7;
56 		stat->total_time >>= 7;
57 	}
58 
59 	/* Set MAX if it's busy enough */
60 	if (stat->busy_time * 100 >
61 	    stat->total_time * dfso_upthreshold) {
62 		*freq = DEVFREQ_MAX_FREQ;
63 		return 0;
64 	}
65 
66 	/* Set MAX if we do not know the initial frequency */
67 	if (stat->current_frequency == 0) {
68 		*freq = DEVFREQ_MAX_FREQ;
69 		return 0;
70 	}
71 
72 	/* Keep the current frequency */
73 	if (stat->busy_time * 100 >
74 	    stat->total_time * (dfso_upthreshold - dfso_downdifferential)) {
75 		*freq = stat->current_frequency;
76 		return 0;
77 	}
78 
79 	/* Set the desired frequency based on the load */
80 	a = stat->busy_time;
81 	a *= stat->current_frequency;
82 	b = div_u64(a, stat->total_time);
83 	b *= 100;
84 	b = div_u64(b, (dfso_upthreshold - dfso_downdifferential / 2));
85 	*freq = (unsigned long) b;
86 
87 	return 0;
88 }
89 
90 static int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
91 				unsigned int event, void *data)
92 {
93 	switch (event) {
94 	case DEVFREQ_GOV_START:
95 		devfreq_monitor_start(devfreq);
96 		break;
97 
98 	case DEVFREQ_GOV_STOP:
99 		devfreq_monitor_stop(devfreq);
100 		break;
101 
102 	case DEVFREQ_GOV_INTERVAL:
103 		devfreq_interval_update(devfreq, (unsigned int *)data);
104 		break;
105 
106 	case DEVFREQ_GOV_SUSPEND:
107 		devfreq_monitor_suspend(devfreq);
108 		break;
109 
110 	case DEVFREQ_GOV_RESUME:
111 		devfreq_monitor_resume(devfreq);
112 		break;
113 
114 	default:
115 		break;
116 	}
117 
118 	return 0;
119 }
120 
121 static struct devfreq_governor devfreq_simple_ondemand = {
122 	.name = DEVFREQ_GOV_SIMPLE_ONDEMAND,
123 	.get_target_freq = devfreq_simple_ondemand_func,
124 	.event_handler = devfreq_simple_ondemand_handler,
125 };
126 
127 static int __init devfreq_simple_ondemand_init(void)
128 {
129 	return devfreq_add_governor(&devfreq_simple_ondemand);
130 }
131 subsys_initcall(devfreq_simple_ondemand_init);
132 
133 static void __exit devfreq_simple_ondemand_exit(void)
134 {
135 	int ret;
136 
137 	ret = devfreq_remove_governor(&devfreq_simple_ondemand);
138 	if (ret)
139 		pr_err("%s: failed remove governor %d\n", __func__, ret);
140 
141 	return;
142 }
143 module_exit(devfreq_simple_ondemand_exit);
144 MODULE_LICENSE("GPL");
145