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ce26c5bb MH |
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/devfreq.h> | |
14 | #include <linux/math64.h> | |
15 | ||
16 | /* Default constants for DevFreq-Simple-Ondemand (DFSO) */ | |
17 | #define DFSO_UPTHRESHOLD (90) | |
18 | #define DFSO_DOWNDIFFERENCTIAL (5) | |
19 | static int devfreq_simple_ondemand_func(struct devfreq *df, | |
20 | unsigned long *freq) | |
21 | { | |
22 | struct devfreq_dev_status stat; | |
23 | int err = df->profile->get_dev_status(df->dev.parent, &stat); | |
24 | unsigned long long a, b; | |
25 | unsigned int dfso_upthreshold = DFSO_UPTHRESHOLD; | |
26 | unsigned int dfso_downdifferential = DFSO_DOWNDIFFERENCTIAL; | |
27 | struct devfreq_simple_ondemand_data *data = df->data; | |
28 | ||
29 | if (err) | |
30 | return err; | |
31 | ||
32 | if (data) { | |
33 | if (data->upthreshold) | |
34 | dfso_upthreshold = data->upthreshold; | |
35 | if (data->downdifferential) | |
36 | dfso_downdifferential = data->downdifferential; | |
37 | } | |
38 | if (dfso_upthreshold > 100 || | |
39 | dfso_upthreshold < dfso_downdifferential) | |
40 | return -EINVAL; | |
41 | ||
42 | /* Assume MAX if it is going to be divided by zero */ | |
43 | if (stat.total_time == 0) { | |
44 | *freq = UINT_MAX; | |
45 | return 0; | |
46 | } | |
47 | ||
48 | /* Prevent overflow */ | |
49 | if (stat.busy_time >= (1 << 24) || stat.total_time >= (1 << 24)) { | |
50 | stat.busy_time >>= 7; | |
51 | stat.total_time >>= 7; | |
52 | } | |
53 | ||
54 | /* Set MAX if it's busy enough */ | |
55 | if (stat.busy_time * 100 > | |
56 | stat.total_time * dfso_upthreshold) { | |
57 | *freq = UINT_MAX; | |
58 | return 0; | |
59 | } | |
60 | ||
61 | /* Set MAX if we do not know the initial frequency */ | |
62 | if (stat.current_frequency == 0) { | |
63 | *freq = UINT_MAX; | |
64 | return 0; | |
65 | } | |
66 | ||
67 | /* Keep the current frequency */ | |
68 | if (stat.busy_time * 100 > | |
69 | stat.total_time * (dfso_upthreshold - dfso_downdifferential)) { | |
70 | *freq = stat.current_frequency; | |
71 | return 0; | |
72 | } | |
73 | ||
74 | /* Set the desired frequency based on the load */ | |
75 | a = stat.busy_time; | |
76 | a *= stat.current_frequency; | |
77 | b = div_u64(a, stat.total_time); | |
78 | b *= 100; | |
79 | b = div_u64(b, (dfso_upthreshold - dfso_downdifferential / 2)); | |
80 | *freq = (unsigned long) b; | |
81 | ||
82 | return 0; | |
83 | } | |
84 | ||
85 | const struct devfreq_governor devfreq_simple_ondemand = { | |
86 | .name = "simple_ondemand", | |
87 | .get_target_freq = devfreq_simple_ondemand_func, | |
88 | }; |