governor_simpleondemand.c
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/*
* linux/drivers/devfreq/governor_simpleondemand.c
*
* Copyright (C) 2011 Samsung Electronics
* MyungJoo Ham <myungjoo.ham@samsung.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/errno.h>
#include <linux/module.h>
#include <linux/devfreq.h>
#include <linux/math64.h>
#include "governor.h"
/* Default constants for DevFreq-Simple-Ondemand (DFSO) */
#define DFSO_UPTHRESHOLD (90)
#define DFSO_DOWNDIFFERENCTIAL (5)
static int devfreq_simple_ondemand_func(struct devfreq *df,
unsigned long *freq)
{
int err;
struct devfreq_dev_status *stat;
unsigned long long a, b;
unsigned int dfso_upthreshold = DFSO_UPTHRESHOLD;
unsigned int dfso_downdifferential = DFSO_DOWNDIFFERENCTIAL;
struct devfreq_simple_ondemand_data *data = df->data;
unsigned long max = (df->max_freq) ? df->max_freq : UINT_MAX;
err = devfreq_update_stats(df);
if (err)
return err;
stat = &df->last_status;
if (data) {
if (data->upthreshold)
dfso_upthreshold = data->upthreshold;
if (data->downdifferential)
dfso_downdifferential = data->downdifferential;
}
if (dfso_upthreshold > 100 ||
dfso_upthreshold < dfso_downdifferential)
return -EINVAL;
/* Assume MAX if it is going to be divided by zero */
if (stat->total_time == 0) {
*freq = max;
return 0;
}
/* Prevent overflow */
if (stat->busy_time >= (1 << 24) || stat->total_time >= (1 << 24)) {
stat->busy_time >>= 7;
stat->total_time >>= 7;
}
/* Set MAX if it's busy enough */
if (stat->busy_time * 100 >
stat->total_time * dfso_upthreshold) {
*freq = max;
return 0;
}
/* Set MAX if we do not know the initial frequency */
if (stat->current_frequency == 0) {
*freq = max;
return 0;
}
/* Keep the current frequency */
if (stat->busy_time * 100 >
stat->total_time * (dfso_upthreshold - dfso_downdifferential)) {
*freq = stat->current_frequency;
return 0;
}
/* Set the desired frequency based on the load */
a = stat->busy_time;
a *= stat->current_frequency;
b = div_u64(a, stat->total_time);
b *= 100;
b = div_u64(b, (dfso_upthreshold - dfso_downdifferential / 2));
*freq = (unsigned long) b;
if (df->min_freq && *freq < df->min_freq)
*freq = df->min_freq;
if (df->max_freq && *freq > df->max_freq)
*freq = df->max_freq;
return 0;
}
static int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
unsigned int event, void *data)
{
switch (event) {
case DEVFREQ_GOV_START:
devfreq_monitor_start(devfreq);
break;
case DEVFREQ_GOV_STOP:
devfreq_monitor_stop(devfreq);
break;
case DEVFREQ_GOV_INTERVAL:
devfreq_interval_update(devfreq, (unsigned int *)data);
break;
case DEVFREQ_GOV_SUSPEND:
devfreq_monitor_suspend(devfreq);
break;
case DEVFREQ_GOV_RESUME:
devfreq_monitor_resume(devfreq);
break;
default:
break;
}
return 0;
}
static struct devfreq_governor devfreq_simple_ondemand = {
.name = "simple_ondemand",
.get_target_freq = devfreq_simple_ondemand_func,
.event_handler = devfreq_simple_ondemand_handler,
};
static int __init devfreq_simple_ondemand_init(void)
{
return devfreq_add_governor(&devfreq_simple_ondemand);
}
subsys_initcall(devfreq_simple_ondemand_init);
static void __exit devfreq_simple_ondemand_exit(void)
{
int ret;
ret = devfreq_remove_governor(&devfreq_simple_ondemand);
if (ret)
pr_err("%s: failed remove governor %d\n", __func__, ret);
return;
}
module_exit(devfreq_simple_ondemand_exit);
MODULE_LICENSE("GPL");