| MyungJoo Ham | ce26c5b | 2011-10-02 00:19:34 +0200 | [diff] [blame] | 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 | }; |