Merge branch 'pm-devfreq' into pm-for-linus

* pm-devfreq:
  PM / devfreq: Add basic governors
  PM / devfreq: Add common sysfs interfaces
  PM: Introduce devfreq: generic DVFS framework with device-specific OPPs
  PM / OPP: Add OPP availability change notifier.

11 files changed, 1001 insertions, 0 deletions

diff --git a/drivers/Kconfig b/drivers/Kconfig
index 95b9e7eefadc..a1efd75070aa 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -130,4 +130,6 @@ source "drivers/iommu/Kconfig"
 
 source "drivers/virt/Kconfig"
 
+source "drivers/devfreq/Kconfig"
+
 endmenu
diff --git a/drivers/Makefile b/drivers/Makefile
index 7fa433a7030c..97c957b50819 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -127,3 +127,5 @@ obj-$(CONFIG_IOMMU_SUPPORT)	+= iommu/
 
 # Virtualization drivers
 obj-$(CONFIG_VIRT_DRIVERS)      += virt/
+
+obj-$(CONFIG_PM_DEVFREQ)        += devfreq/
diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c
index b23de185cb04..434a6c011675 100644
--- a/drivers/base/power/opp.c
+++ b/drivers/base/power/opp.c
@@ -73,6 +73,7 @@ struct opp {
  *              RCU usage: nodes are not modified in the list of device_opp,
  *              however addition is possible and is secured by dev_opp_list_lock
  * @dev:        device pointer
+ * @head:       notifier head to notify the OPP availability changes.
  * @opp_list:   list of opps
  *
  * This is an internal data structure maintaining the link to opps attached to
@@ -83,6 +84,7 @@ struct device_opp {
         struct list_head node;
 
         struct device *dev;
+        struct srcu_notifier_head head;
         struct list_head opp_list;
 };
 
@@ -404,6 +406,7 @@ int opp_add(struct device *dev, unsigned long freq, unsigned long u_volt)
                 }
 
                 dev_opp->dev = dev;
+                srcu_init_notifier_head(&dev_opp->head);
                 INIT_LIST_HEAD(&dev_opp->opp_list);
 
                 /* Secure the device list modification */
@@ -428,6 +431,11 @@ int opp_add(struct device *dev, unsigned long freq, unsigned long u_volt)
         list_add_rcu(&new_opp->node, head);
         mutex_unlock(&dev_opp_list_lock);
 
+        /*
+         * Notify the changes in the availability of the operable
+         * frequency/voltage list.
+         */
+        srcu_notifier_call_chain(&dev_opp->head, OPP_EVENT_ADD, new_opp);
         return 0;
 }
 
@@ -504,6 +512,14 @@ static int opp_set_availability(struct device *dev, unsigned long freq,
         mutex_unlock(&dev_opp_list_lock);
         synchronize_rcu();
 
+        /* Notify the change of the OPP availability */
+        if (availability_req)
+                srcu_notifier_call_chain(&dev_opp->head, OPP_EVENT_ENABLE,
+                                         new_opp);
+        else
+                srcu_notifier_call_chain(&dev_opp->head, OPP_EVENT_DISABLE,
+                                         new_opp);
+
         /* clean up old opp */
         new_opp = opp;
         goto out;
@@ -643,3 +659,17 @@ void opp_free_cpufreq_table(struct device *dev,
         *table = NULL;
 }
 #endif          /* CONFIG_CPU_FREQ */
+
+/**
+ * opp_get_notifier() - find notifier_head of the device with opp
+ * @dev:        device pointer used to lookup device OPPs.
+ */
+struct srcu_notifier_head *opp_get_notifier(struct device *dev)
+{
+        struct device_opp *dev_opp = find_device_opp(dev);
+
+        if (IS_ERR(dev_opp))
+                return ERR_PTR(PTR_ERR(dev_opp)); /* matching type */
+
+        return &dev_opp->head;
+}
diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
new file mode 100644
index 000000000000..643b055ed3cd
--- /dev/null
+++ b/drivers/devfreq/Kconfig
@@ -0,0 +1,75 @@
+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 Governors"
+
+config DEVFREQ_GOV_SIMPLE_ONDEMAND
+        bool "Simple Ondemand"
+        help
+          Chooses frequency based on the recent load on the device. Works
+          similar as ONDEMAND governor of CPUFREQ does. A device with
+          Simple-Ondemand should be able to provide busy/total counter
+          values that imply the usage rate. A device may provide tuned
+          values to the governor with data field at devfreq_add_device().
+
+config DEVFREQ_GOV_PERFORMANCE
+        bool "Performance"
+        help
+          Sets the frequency at the maximum available frequency.
+          This governor always returns UINT_MAX as frequency so that
+          the DEVFREQ framework returns the highest frequency available
+          at any time.
+
+config DEVFREQ_GOV_POWERSAVE
+        bool "Powersave"
+        help
+          Sets the frequency at the minimum available frequency.
+          This governor always returns 0 as frequency so that
+          the DEVFREQ framework returns the lowest frequency available
+          at any time.
+
+config DEVFREQ_GOV_USERSPACE
+        bool "Userspace"
+        help
+          Sets the frequency at the user specified one.
+          This governor returns the user configured frequency if there
+          has been an input to /sys/devices/.../power/devfreq_set_freq.
+          Otherwise, the governor does not change the frequnecy
+          given at the initialization.
+
+comment "DEVFREQ Drivers"
+
+endif # PM_DEVFREQ
diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
new file mode 100644
index 000000000000..4564a89e970a
--- /dev/null
+++ b/drivers/devfreq/Makefile
@@ -0,0 +1,5 @@
+obj-$(CONFIG_PM_DEVFREQ)        += devfreq.o
+obj-$(CONFIG_DEVFREQ_GOV_SIMPLE_ONDEMAND)       += governor_simpleondemand.o
+obj-$(CONFIG_DEVFREQ_GOV_PERFORMANCE)   += governor_performance.o
+obj-$(CONFIG_DEVFREQ_GOV_POWERSAVE)     += governor_powersave.o
+obj-$(CONFIG_DEVFREQ_GOV_USERSPACE)     += governor_userspace.o
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
new file mode 100644
index 000000000000..5d15b812377b
--- /dev/null
+++ b/drivers/devfreq/devfreq.c
@@ -0,0 +1,601 @@
+/*
+ * 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;
+}
+
+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");
diff --git a/drivers/devfreq/governor.h b/drivers/devfreq/governor.h
new file mode 100644
index 000000000000..ea7f13c58ded
--- /dev/null
+++ b/drivers/devfreq/governor.h
@@ -0,0 +1,24 @@
+/*
+ * governor.h - internal header for devfreq governors.
+ *
+ * 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.
+ *
+ * This header is for devfreq governors in drivers/devfreq/
+ */
+
+#ifndef _GOVERNOR_H
+#define _GOVERNOR_H
+
+#include <linux/devfreq.h>
+
+#define to_devfreq(DEV) container_of((DEV), struct devfreq, dev)
+
+/* Caution: devfreq->lock must be locked before calling update_devfreq */
+extern int update_devfreq(struct devfreq *devfreq);
+
+#endif /* _GOVERNOR_H */
diff --git a/drivers/devfreq/governor_performance.c b/drivers/devfreq/governor_performance.c
new file mode 100644
index 000000000000..c0596b291761
--- /dev/null
+++ b/drivers/devfreq/governor_performance.c
@@ -0,0 +1,29 @@
+/*
+ *  linux/drivers/devfreq/governor_performance.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/devfreq.h>
+
+static int devfreq_performance_func(struct devfreq *df,
+                                    unsigned long *freq)
+{
+        /*
+         * target callback should be able to get floor value as
+         * said in devfreq.h
+         */
+        *freq = UINT_MAX;
+        return 0;
+}
+
+const struct devfreq_governor devfreq_performance = {
+        .name = "performance",
+        .get_target_freq = devfreq_performance_func,
+        .no_central_polling = true,
+};
diff --git a/drivers/devfreq/governor_powersave.c b/drivers/devfreq/governor_powersave.c
new file mode 100644
index 000000000000..2483a85a266f
--- /dev/null
+++ b/drivers/devfreq/governor_powersave.c
@@ -0,0 +1,29 @@
+/*
+ *  linux/drivers/devfreq/governor_powersave.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/devfreq.h>
+
+static int devfreq_powersave_func(struct devfreq *df,
+                                  unsigned long *freq)
+{
+        /*
+         * target callback should be able to get ceiling value as
+         * said in devfreq.h
+         */
+        *freq = 0;
+        return 0;
+}
+
+const struct devfreq_governor devfreq_powersave = {
+        .name = "powersave",
+        .get_target_freq = devfreq_powersave_func,
+        .no_central_polling = true,
+};
diff --git a/drivers/devfreq/governor_simpleondemand.c b/drivers/devfreq/governor_simpleondemand.c
new file mode 100644
index 000000000000..efad8dcf9028
--- /dev/null
+++ b/drivers/devfreq/governor_simpleondemand.c
@@ -0,0 +1,88 @@
+/*
+ *  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/devfreq.h>
+#include <linux/math64.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)
+{
+        struct devfreq_dev_status stat;
+        int err = df->profile->get_dev_status(df->dev.parent, &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;
+
+        if (err)
+                return err;
+
+        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 = UINT_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 = UINT_MAX;
+                return 0;
+        }
+
+        /* Set MAX if we do not know the initial frequency */
+        if (stat.current_frequency == 0) {
+                *freq = UINT_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;
+
+        return 0;
+}
+
+const struct devfreq_governor devfreq_simple_ondemand = {
+        .name = "simple_ondemand",
+        .get_target_freq = devfreq_simple_ondemand_func,
+};
diff --git a/drivers/devfreq/governor_userspace.c b/drivers/devfreq/governor_userspace.c
new file mode 100644
index 000000000000..4f8b563da782
--- /dev/null
+++ b/drivers/devfreq/governor_userspace.c
@@ -0,0 +1,116 @@
+/*
+ *  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/slab.h>
+#include <linux/device.h>
+#include <linux/devfreq.h>
+#include <linux/pm.h>
+#include <linux/mutex.h>
+#include "governor.h"
+
+struct userspace_data {
+        unsigned long user_frequency;
+        bool valid;
+};
+
+static int devfreq_userspace_func(struct devfreq *df, unsigned long *freq)
+{
+        struct userspace_data *data = df->data;
+
+        if (!data->valid)
+                *freq = df->previous_freq; /* No user freq specified yet */
+        else
+                *freq = data->user_frequency;
+        return 0;
+}
+
+static ssize_t store_freq(struct device *dev, struct device_attribute *attr,
+                          const char *buf, size_t count)
+{
+        struct devfreq *devfreq = to_devfreq(dev);
+        struct userspace_data *data;
+        unsigned long wanted;
+        int err = 0;
+
+
+        mutex_lock(&devfreq->lock);
+        data = devfreq->data;
+
+        sscanf(buf, "%lu", &wanted);
+        data->user_frequency = wanted;
+        data->valid = true;
+        err = update_devfreq(devfreq);
+        if (err == 0)
+                err = count;
+        mutex_unlock(&devfreq->lock);
+        return err;
+}
+
+static ssize_t show_freq(struct device *dev, struct device_attribute *attr,
+                         char *buf)
+{
+        struct devfreq *devfreq = to_devfreq(dev);
+        struct userspace_data *data;
+        int err = 0;
+
+        mutex_lock(&devfreq->lock);
+        data = devfreq->data;
+
+        if (data->valid)
+                err = sprintf(buf, "%lu\n", data->user_frequency);
+        else
+                err = sprintf(buf, "undefined\n");
+        mutex_unlock(&devfreq->lock);
+        return err;
+}
+
+static DEVICE_ATTR(set_freq, 0644, show_freq, store_freq);
+static struct attribute *dev_entries[] = {
+        &dev_attr_set_freq.attr,
+        NULL,
+};
+static struct attribute_group dev_attr_group = {
+        .name   = "userspace",
+        .attrs  = dev_entries,
+};
+
+static int userspace_init(struct devfreq *devfreq)
+{
+        int err = 0;
+        struct userspace_data *data = kzalloc(sizeof(struct userspace_data),
+                                              GFP_KERNEL);
+
+        if (!data) {
+                err = -ENOMEM;
+                goto out;
+        }
+        data->valid = false;
+        devfreq->data = data;
+
+        err = sysfs_create_group(&devfreq->dev.kobj, &dev_attr_group);
+out:
+        return err;
+}
+
+static void userspace_exit(struct devfreq *devfreq)
+{
+        sysfs_remove_group(&devfreq->dev.kobj, &dev_attr_group);
+        kfree(devfreq->data);
+        devfreq->data = NULL;
+}
+
+const struct devfreq_governor devfreq_userspace = {
+        .name = "userspace",
+        .get_target_freq = devfreq_userspace_func,
+        .init = userspace_init,
+        .exit = userspace_exit,
+        .no_central_polling = true,
+};