drivers/devfreq/governor_simpleondemand.c

   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");