linux/drivers/devfreq/governor_simpleondemand.c
Chanwoo Choi 5f1a9066fc PM / devfreq: Add governor attribute flag for specifc sysfs nodes
DEVFREQ supports the default governors like performance, simple_ondemand and
also allows the devfreq driver to add their own governor like tegra30-devfreq.c
according to their requirement. In result, some sysfs attributes are useful
or not useful. Prior to that the user can access all sysfs attributes
regardless of the available attributes.

So, clarify the access permission of sysfs attributes according to governor.
When adding the devfreq governor, can specify the available attribute
information by using DEVFREQ_GOV_ATTR_* constant variable. The user can
read or write the sysfs attributes in accordance to the specified attributes.

When adding the governor, can add the following attributes
according to the governor feature.

[Definition for speific sysfs attributes]
- DEVFREQ_GOV_ATTR_POLLING_INTERVAL to update polling interval for timer.
  : /sys/class/devfreq/[devfreq dev name]/polling_interval
- DEVFREQ_GOV_ATTR_TIMER to change the type of timer on either deferrable
  or dealyed timer.
  : /sys/class/devfreq/[devfreq dev name]/timer

And all devfreq governors have to support the following common attributes.
The common attributes are added to devfreq class by default.
- governor
- available_governors
- available_frequencies
- cur_freq
- target_freq
- min_freq
- max_freq
- trans_stat

[Table of governor attribute flags for devfreq governors]
------------------------------------------------------------------------------
                      | simple    | perfor | power | user | passive | tegra30
		      | ondemand  | mance  | save  | space|         |
------------------------------------------------------------------------------
governor              | O         | O      | O     | O    | O       | O
available_governors   | O         | O      | O     | O    | O       | O
available_frequencies | O         | O      | O     | O    | O       | O
cur_freq              | O         | O      | O     | O    | O       | O
target_freq           | O         | O      | O     | O    | O       | O
min_freq              | O         | O      | O     | O    | O       | O
max_freq              | O         | O      | O     | O    | O       | O
trans_stat            | O         | O      | O     | O    | O       | O
                      --------------------------------------------------------
polling_interval      | O         | X      | X     | X    | X       | O
timer                 | O         | X      | X     | X    | X       | X
------------------------------------------------------------------------------

Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
Tested-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
2020-10-26 11:46:54 +09:00

144 lines
3.3 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* linux/drivers/devfreq/governor_simpleondemand.c
*
* Copyright (C) 2011 Samsung Electronics
* MyungJoo Ham <myungjoo.ham@samsung.com>
*/
#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;
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 = DEVFREQ_MAX_FREQ;
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 = DEVFREQ_MAX_FREQ;
return 0;
}
/* Set MAX if we do not know the initial frequency */
if (stat->current_frequency == 0) {
*freq = DEVFREQ_MAX_FREQ;
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;
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_UPDATE_INTERVAL:
devfreq_update_interval(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 = DEVFREQ_GOV_SIMPLE_ONDEMAND,
.attrs = DEVFREQ_GOV_ATTR_POLLING_INTERVAL
| DEVFREQ_GOV_ATTR_TIMER,
.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");