- 根目录:
- drivers
- devfreq
- devfreq.c
/*
* devfreq: Generic Dynamic Voltage and Frequency Scaling (DVFS) Framework
* for Non-CPU Devices.
*
* 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/kernel.h>
#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/stat.h>
#include <linux/opp.h>
#include <linux/devfreq.h>
#include <linux/workqueue.h>
#include <linux/platform_device.h>
#include <linux/list.h>
#include <linux/printk.h>
#include <linux/hrtimer.h>
#include "governor.h"
struct class *devfreq_class;
/*
* devfreq_work periodically monitors every registered device.
* The minimum polling interval is one jiffy. The polling interval is
* determined by the minimum polling period among all polling devfreq
* devices. The resolution of polling interval is one jiffy.
*/
static bool polling;
static struct workqueue_struct *devfreq_wq;
static struct delayed_work devfreq_work;
/* wait removing if this is to be removed */
static struct devfreq *wait_remove_device;
/* The list of all device-devfreq */
static LIST_HEAD(devfreq_list);
static DEFINE_MUTEX(devfreq_list_lock);
/**
* find_device_devfreq() - find devfreq struct using device pointer
* @dev: device pointer used to lookup device devfreq.
*
* Search the list of device devfreqs and return the matched device's
* devfreq info. devfreq_list_lock should be held by the caller.
*/
static struct devfreq *find_device_devfreq(struct device *dev)
{
struct devfreq *tmp_devfreq;
if (unlikely(IS_ERR_OR_NULL(dev))) {
pr_err("DEVFREQ: %s: Invalid parameters\n", __func__);
return ERR_PTR(-EINVAL);
}
WARN(!mutex_is_locked(&devfreq_list_lock),
"devfreq_list_lock must be locked.");
list_for_each_entry(tmp_devfreq, &devfreq_list, node) {
if (tmp_devfreq->dev.parent == dev)
return tmp_devfreq;
}
return ERR_PTR(-ENODEV);
}
/**
* update_devfreq() - Reevaluate the device and configure frequency.
* @devfreq: the devfreq instance.
*
* Note: Lock devfreq->lock before calling update_devfreq
* This function is exported for governors.
*/
int update_devfreq(struct devfreq *devfreq)
{
unsigned long freq;
int err = 0;
if (!mutex_is_locked(&devfreq->lock)) {
WARN(true, "devfreq->lock must be locked by the caller.\n");
return -EINVAL;
}
/* Reevaluate the proper frequency */
err = devfreq->governor->get_target_freq(devfreq, &freq);
if (err)
return err;
err = devfreq->profile->target(devfreq->dev.parent, &freq);
if (err)
return err;
devfreq->previous_freq = freq;
return err;
}
/**
* devfreq_notifier_call() - Notify that the device frequency requirements
* has been changed out of devfreq framework.
* @nb the notifier_block (supposed to be devfreq->nb)
* @type not used
* @devp not used
*
* Called by a notifier that uses devfreq->nb.
*/
static int devfreq_notifier_call(struct notifier_block *nb, unsigned long type,
void *devp)
{
struct devfreq *devfreq = container_of(nb, struct devfreq, nb);
int ret;
mutex_lock(&devfreq->lock);
ret = update_devfreq(devfreq);
mutex_unlock(&devfreq->lock);
return ret;
}
/**
* _remove_devfreq() - Remove devfreq from the device.
* @devfreq: the devfreq struct
* @skip: skip calling device_unregister().
*
* Note that the caller should lock devfreq->lock before calling
* this. _remove_devfreq() will unlock it and free devfreq
* internally. devfreq_list_lock should be locked by the caller
* as well (not relased at return)
*
* Lock usage:
* devfreq->lock: locked before call.
* unlocked at return (and freed)
* devfreq_list_lock: locked before call.
* kept locked at return.
* if devfreq is centrally polled.
*
* Freed memory:
* devfreq
*/
static void _remove_devfreq(struct devfreq *devfreq, bool skip)
{
if (!mutex_is_locked(&devfreq->lock)) {
WARN(true, "devfreq->lock must be locked by the caller.\n");
return;
}
if (!devfreq->governor->no_central_polling &&
!mutex_is_locked(&devfreq_list_lock)) {
WARN(true, "devfreq_list_lock must be locked by the caller.\n");
return;
}
if (devfreq->being_removed)
return;
devfreq->being_removed = true;
if (devfreq->profile->exit)
devfreq->profile->exit(devfreq->dev.parent);
if (devfreq->governor->exit)
devfreq->governor->exit(devfreq);
if (!skip && get_device(&devfreq->dev)) {
device_unregister(&devfreq->dev);
put_device(&devfreq->dev);
}
if (!devfreq->governor->no_central_polling)
list_del(&devfreq->node);
mutex_unlock(&devfreq->lock);
mutex_destroy(&devfreq->lock);
kfree(devfreq);
}
/**
* devfreq_dev_release() - Callback for struct device to release the device.
* @dev: the devfreq device
*
* This calls _remove_devfreq() if _remove_devfreq() is not called.
* Note that devfreq_dev_release() could be called by _remove_devfreq() as
* well as by others unregistering the device.
*/
static void devfreq_dev_release(struct device *dev)
{
struct devfreq *devfreq = to_devfreq(dev);
bool central_polling = !devfreq->governor->no_central_polling;
/*
* If devfreq_dev_release() was called by device_unregister() of
* _remove_devfreq(), we cannot mutex_lock(&devfreq->lock) and
* being_removed is already set. This also partially checks the case
* where devfreq_dev_release() is called from a thread other than
* the one called _remove_devfreq(); however, this case is
* dealt completely with another following being_removed check.
*
* Because being_removed is never being
* unset, we do not need to worry about race conditions on
* being_removed.
*/
if (devfreq->being_removed)
return;
if (central_polling)
mutex_lock(&devfreq_list_lock);
mutex_lock(&devfreq->lock);
/*
* Check being_removed flag again for the case where
* devfreq_dev_release() was called in a thread other than the one
* possibly called _remove_devfreq().
*/
if (devfreq->being_removed) {
mutex_unlock(&devfreq->lock);
goto out;
}
/* devfreq->lock is unlocked and removed in _removed_devfreq() */
_remove_devfreq(devfreq, true);
out:
if (central_polling)
mutex_unlock(&devfreq_list_lock);
}
/**
* devfreq_monitor() - Periodically poll devfreq objects.
* @work: the work struct used to run devfreq_monitor periodically.
*
*/
static void devfreq_monitor(struct work_struct *work)
{
static unsigned long last_polled_at;
struct devfreq *devfreq, *tmp;
int error;
unsigned long jiffies_passed;
unsigned long next_jiffies = ULONG_MAX, now = jiffies;
struct device *dev;
/* Initially last_polled_at = 0, polling every device at bootup */
jiffies_passed = now - last_polled_at;
last_polled_at = now;
if (jiffies_passed == 0)
jiffies_passed = 1;
mutex_lock(&devfreq_list_lock);
list_for_each_entry_safe(devfreq, tmp, &devfreq_list, node) {
mutex_lock(&devfreq->lock);
dev = devfreq->dev.parent;
/* Do not remove tmp for a while */
wait_remove_device = tmp;
if (devfreq->governor->no_central_polling ||
devfreq->next_polling == 0) {
mutex_unlock(&devfreq->lock);
continue;
}
mutex_unlock(&devfreq_list_lock);
/*
* Reduce more next_polling if devfreq_wq took an extra
* delay. (i.e., CPU has been idled.)
*/
if (devfreq->next_polling <= jiffies_passed) {
error = update_devfreq(devfreq);
/* Remove a devfreq with an error. */
if (error && error != -EAGAIN) {
dev_err(dev, "Due to update_devfreq error(%d), devfreq(%s) is removed from the device\n",
error, devfreq->governor->name);
/*
* Unlock devfreq before locking the list
* in order to avoid deadlock with
* find_device_devfreq or others
*/
mutex_unlock(&devfreq->lock);
mutex_lock(&devfreq_list_lock);
/* Check if devfreq is already removed */
if (IS_ERR(find_device_devfreq(dev)))
continue;
mutex_lock(&devfreq->lock);
/* This unlocks devfreq->lock and free it */
_remove_devfreq(devfreq, false);
continue;
}
devfreq->next_polling = devfreq->polling_jiffies;
} else {
devfreq->next_polling -= jiffies_passed;
}
if (devfreq->next_polling)
next_jiffies = (next_jiffies > devfreq->next_polling) ?
devfreq->next_polling : next_jiffies;
mutex_unlock(&devfreq->lock);
mutex_lock(&devfreq_list_lock);
}
wait_remove_device = NULL;
mutex_unlock(&devfreq_list_lock);
if (next_jiffies > 0 && next_jiffies < ULONG_MAX) {
polling = true;
queue_delayed_work(devfreq_wq, &devfreq_work, next_jiffies);
} else {
polling = false;
}
}
/**
* devfreq_add_device() - Add devfreq feature to the device
* @dev: the device to add devfreq feature.
* @profile: device-specific profile to run devfreq.
* @governor: the policy to choose frequency.
* @data: private data for the governor. The devfreq framework does not
* touch this value.
*/
struct devfreq *devfreq_add_device(struct device *dev,
struct devfreq_dev_profile *profile,
const struct devfreq_governor *governor,
void *data)
{
struct devfreq *devfreq;
int err = 0;
if (!dev || !profile || !governor) {
dev_err(dev, "%s: Invalid parameters.\n", __func__);
return ERR_PTR(-EINVAL);
}
if (!governor->no_central_polling) {
mutex_lock(&devfreq_list_lock);
devfreq = find_device_devfreq(dev);
mutex_unlock(&devfreq_list_lock);
if (!IS_ERR(devfreq)) {
dev_err(dev, "%s: Unable to create devfreq for the device. It already has one.\n", __func__);
err = -EINVAL;
goto err_out;
}
}
devfreq = kzalloc(sizeof(struct devfreq), GFP_KERNEL);
if (!devfreq) {
dev_err(dev, "%s: Unable to create devfreq for the device\n",
__func__);
err = -ENOMEM;
goto err_out;
}
mutex_init(&devfreq->lock);
mutex_lock(&devfreq->lock);
devfreq->dev.parent = dev;
devfreq->dev.class = devfreq_class;
devfreq->dev.release = devfreq_dev_release;
devfreq->profile = profile;
devfreq->governor = governor;
devfreq->previous_freq = profile->initial_freq;
devfreq->data = data;
devfreq->next_polling = devfreq->polling_jiffies
= msecs_to_jiffies(devfreq->profile->polling_ms);
devfreq->nb.notifier_call = devfreq_notifier_call;
dev_set_name(&devfreq->dev, dev_name(dev));
err = device_register(&devfreq->dev);
if (err) {
put_device(&devfreq->dev);
goto err_dev;
}
if (governor->init)
err = governor->init(devfreq);
if (err)
goto err_init;
mutex_unlock(&devfreq->lock);
if (governor->no_central_polling)
goto out;
mutex_lock(&devfreq_list_lock);
list_add(&devfreq->node, &devfreq_list);
if (devfreq_wq && devfreq->next_polling && !polling) {
polling = true;
queue_delayed_work(devfreq_wq, &devfreq_work,
devfreq->next_polling);
}
mutex_unlock(&devfreq_list_lock);
out:
return devfreq;
err_init:
device_unregister(&devfreq->dev);
err_dev:
mutex_unlock(&devfreq->lock);
kfree(devfreq);
err_out:
return ERR_PTR(err);
}
/**
* devfreq_remove_device() - Remove devfreq feature from a device.
* @devfreq the devfreq instance to be removed
*/
int devfreq_remove_device(struct devfreq *devfreq)
{
bool central_polling;
if (!devfreq)
return -EINVAL;
central_polling = !devfreq->governor->no_central_polling;
if (central_polling) {
mutex_lock(&devfreq_list_lock);
while (wait_remove_device == devfreq) {
mutex_unlock(&devfreq_list_lock);
schedule();
mutex_lock(&devfreq_list_lock);
}
}
mutex_lock(&devfreq->lock);
_remove_devfreq(devfreq, false); /* it unlocks devfreq->lock */
if (central_polling)
mutex_unlock(&devfreq_list_lock);
return 0;
}
static ssize_t show_governor(struct device *dev,
struct device_attribute *attr, char *buf)
{
return sprintf(buf, "%s\n", to_devfreq(dev)->governor->name);
}
static ssize_t show_freq(struct device *dev,
struct device_attribute *attr, char *buf)
{
return sprintf(buf, "%lu\n", to_devfreq(dev)->previous_freq);
}
static ssize_t show_polling_interval(struct device *dev,
struct device_attribute *attr, char *buf)
{
return sprintf(buf, "%d\n", to_devfreq(dev)->profile->polling_ms);
}
static ssize_t store_polling_interval(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t count)
{
struct devfreq *df = to_devfreq(dev);
unsigned int value;
int ret;
ret = sscanf(buf, "%u", &value);
if (ret != 1)
goto out;
mutex_lock(&df->lock);
df->profile->polling_ms = value;
df->next_polling = df->polling_jiffies
= msecs_to_jiffies(value);
mutex_unlock(&df->lock);
ret = count;
if (df->governor->no_central_polling)
goto out;
mutex_lock(&devfreq_list_lock);
if (df->next_polling > 0 && !polling) {
polling = true;
queue_delayed_work(devfreq_wq, &devfreq_work,
df->next_polling);
}
mutex_unlock(&devfreq_list_lock);
out:
return ret;
}
static ssize_t show_central_polling(struct device *dev,
struct device_attribute *attr, char *buf)
{
return sprintf(buf, "%d\n",
!to_devfreq(dev)->governor->no_central_polling);
}
static struct device_attribute devfreq_attrs[] = {
__ATTR(governor, S_IRUGO, show_governor, NULL),
__ATTR(cur_freq, S_IRUGO, show_freq, NULL),
__ATTR(central_polling, S_IRUGO, show_central_polling, NULL),
__ATTR(polling_interval, S_IRUGO | S_IWUSR, show_polling_interval,
store_polling_interval),
{ },
};
/**
* devfreq_start_polling() - Initialize data structure for devfreq framework and
* start polling registered devfreq devices.
*/
static int __init devfreq_start_polling(void)
{
mutex_lock(&devfreq_list_lock);
polling = false;
devfreq_wq = create_freezable_workqueue("devfreq_wq");
INIT_DELAYED_WORK_DEFERRABLE(&devfreq_work, devfreq_monitor);
mutex_unlock(&devfreq_list_lock);
devfreq_monitor(&devfreq_work.work);
return 0;
}
late_initcall(devfreq_start_polling);
static int __init devfreq_init(void)
{
devfreq_class = class_create(THIS_MODULE, "devfreq");
if (IS_ERR(devfreq_class)) {
pr_err("%s: couldn't create class\n", __FILE__);
return PTR_ERR(devfreq_class);
}
devfreq_class->dev_attrs = devfreq_attrs;
return 0;
}
subsys_initcall(devfreq_init);
static void __exit devfreq_exit(void)
{
class_destroy(devfreq_class);
}
module_exit(devfreq_exit);
/*
* The followings are helper functions for devfreq user device drivers with
* OPP framework.
*/
/**
* devfreq_recommended_opp() - Helper function to get proper OPP for the
* freq value given to target callback.
* @dev The devfreq user device. (parent of devfreq)
* @freq The frequency given to target function
*
*/
struct opp *devfreq_recommended_opp(struct device *dev, unsigned long *freq)
{
struct opp *opp = opp_find_freq_ceil(dev, freq);
if (opp == ERR_PTR(-ENODEV))
opp = opp_find_freq_floor(dev, freq);
return opp;
}
/**
* devfreq_register_opp_notifier() - Helper function to get devfreq notified
* for any changes in the OPP availability
* changes
* @dev The devfreq user device. (parent of devfreq)
* @devfreq The devfreq object.
*/
int devfreq_register_opp_notifier(struct device *dev, struct devfreq *devfreq)
{
struct srcu_notifier_head *nh = opp_get_notifier(dev);
if (IS_ERR(nh))
return PTR_ERR(nh);
return srcu_notifier_chain_register(nh, &devfreq->nb);
}
/**
* devfreq_unregister_opp_notifier() - Helper function to stop getting devfreq
* notified for any changes in the OPP
* availability changes anymore.
* @dev The devfreq user device. (parent of devfreq)
* @devfreq The devfreq object.
*
* At exit() callback of devfreq_dev_profile, this must be included if
* devfreq_recommended_opp is used.
*/
int devfreq_unregister_opp_notifier(struct device *dev, struct devfreq *devfreq)
{
struct srcu_notifier_head *nh = opp_get_notifier(dev);
if (IS_ERR(nh))
return PTR_ERR(nh);
return srcu_notifier_chain_unregister(nh, &devfreq->nb);
}
MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
MODULE_DESCRIPTION("devfreq class support");
MODULE_LICENSE("GPL");