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