PM: Introduce devfreq: generic DVFS framework with device-specific OPPs

source "drivers/virt/Kconfig"

source "drivers/devfreq/Kconfig"

endmenu

# Virtualization drivers

obj-$(CONFIG_VIRT_DRIVERS)	+= virt/

obj-$(CONFIG_PM_DEVFREQ)	+= devfreq/

config ARCH_HAS_DEVFREQ

	bool

	depends on ARCH_HAS_OPP

	help

	  Denotes that the architecture supports DEVFREQ. If the architecture

	  supports multiple OPP entries per device and the frequency of the

	  devices with OPPs may be altered dynamically, the architecture

	  supports DEVFREQ.

menuconfig PM_DEVFREQ

	bool "Generic Dynamic Voltage and Frequency Scaling (DVFS) support"

	depends on PM_OPP && ARCH_HAS_DEVFREQ

	help

	  With OPP support, a device may have a list of frequencies and

	  voltages available. DEVFREQ, a generic DVFS framework can be

	  registered for a device with OPP support in order to let the

	  governor provided to DEVFREQ choose an operating frequency

	  based on the OPP's list and the policy given with DEVFREQ.

	  Each device may have its own governor and policy. DEVFREQ can

	  reevaluate the device state periodically and/or based on the

	  OPP list changes (each frequency/voltage pair in OPP may be

	  disabled or enabled).

	  Like some CPUs with CPUFREQ, a device may have multiple clocks.

	  However, because the clock frequencies of a single device are

	  determined by the single device's state, an instance of DEVFREQ

	  is attached to a single device and returns a "representative"

	  clock frequency from the OPP of the device, which is also attached

	  to a device by 1-to-1. The device registering DEVFREQ takes the

	  responsiblity to "interpret" the frequency listed in OPP and

	  to set its every clock accordingly with the "target" callback

	  given to DEVFREQ.

if PM_DEVFREQ

comment "DEVFREQ Drivers"

endif # PM_DEVFREQ

obj-$(CONFIG_PM_DEVFREQ)	+= devfreq.o

/*

 * 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/slab.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 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 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);

	goto out;

err_init:

	device_unregister(&devfreq->dev);

err_dev:

	mutex_unlock(&devfreq->lock);

	kfree(devfreq);

out:

	if (err)

		return ERR_PTR(err);

	else

		return devfreq;

}

/**

 * devfreq_remove_device() - Remove devfreq feature from a device.

 * @devfreq	the devfreq instance to be removed

 */

int devfreq_remove_device(struct devfreq *devfreq)

{

	if (!devfreq)

		return -EINVAL;

	if (!devfreq->governor->no_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 (!devfreq->governor->no_central_polling)

		mutex_unlock(&devfreq_list_lock);

	return 0;

}

/**

 * 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);

	}

	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");