PM / devfreq: event: Add devfreq_event class

This patch adds a new class in devfreq, devfreq_event, which provides
raw data (e.g., memory bus utilization, GPU utilization) for devfreq
governors.

- devfreq_event device : Provides raw data for a governor of a devfreq device
- devfreq device       : Monitors device state and changes frequency/voltage
			of the device using the raw data from its
			devfreq_event device.

A devfreq device dertermines performance states (normally the frequency
and the voltage vlues) based on the results its designtated devfreq governor:
e.g., ondemand, performance, powersave.

In order to give such results required by a devfreq device, the devfreq
governor requires data that indicates the performance requirement given
to the devfreq device. The conventional (previous) implementatino of
devfreq subsystem requires a devfreq device driver to implement its own
mechanism to acquire performance requirement for its governor. However,
there had been issues with such requirements:

1. Although performance requirement of such devices is usually acquired
 from common devices (PMU/PPMU), we do not have any abstract structure to
 represent them properly.
2. Such performance requirement devices (PMU/PPMU) are actual hardware
 pieces that may be represented by Device Tree directly while devfreq device
 itself is a virtual entity that are not considered to be represented by
 Device Tree according to Device Tree folks.

In order to address such issues, a devferq_event device (represented by
this patch) provides a template for device drivers representing
performance monitoring unit, which gives the basic or raw data for
preformance requirement, which in turn, is required by devfreq governors.

The following description explains the feature of two kind of devfreq class:
- devfreq class (existing)
 : devfreq consumer device use raw data from devfreq_event device for
   determining proper current system state and change voltage/frequency
   dynamically using various governors.

- devfreq_event class (new)
 : Provide measured raw data to devfreq device for governor

Cc: MyungJoo Ham <myungjoo.ham@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
[Commit message rewritten & conflict resolved by MyungJoo]
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>

1 files changed, 494 insertions, 0 deletions

diff --git a/drivers/devfreq/devfreq-event.c b/drivers/devfreq/devfreq-event.c
new file mode 100644
index 000000000000..f304a0289eda
--- /dev/null
+++ b/drivers/devfreq/devfreq-event.c
@@ -0,0 +1,494 @@
+/*
+ * devfreq-event: a framework to provide raw data and events of devfreq devices
+ *
+ * Copyright (C) 2015 Samsung Electronics
+ * Author: Chanwoo Choi <cw00.choi@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 driver is based on drivers/devfreq/devfreq.c.
+ */
+
+#include <linux/devfreq-event.h>
+#include <linux/kernel.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/list.h>
+#include <linux/of.h>
+
+static struct class *devfreq_event_class;
+
+/* The list of all devfreq event list */
+static LIST_HEAD(devfreq_event_list);
+static DEFINE_MUTEX(devfreq_event_list_lock);
+
+#define to_devfreq_event(DEV) container_of(DEV, struct devfreq_event_dev, dev)
+
+/**
+ * devfreq_event_enable_edev() - Enable the devfreq-event dev and increase
+ *                               the enable_count of devfreq-event dev.
+ * @edev        : the devfreq-event device
+ *
+ * Note that this function increase the enable_count and enable the
+ * devfreq-event device. The devfreq-event device should be enabled before
+ * using it by devfreq device.
+ */
+int devfreq_event_enable_edev(struct devfreq_event_dev *edev)
+{
+        int ret = 0;
+
+        if (!edev || !edev->desc)
+                return -EINVAL;
+
+        mutex_lock(&edev->lock);
+        if (edev->desc->ops && edev->desc->ops->enable
+                        && edev->enable_count == 0) {
+                ret = edev->desc->ops->enable(edev);
+                if (ret < 0)
+                        goto err;
+        }
+        edev->enable_count++;
+err:
+        mutex_unlock(&edev->lock);
+
+        return ret;
+}
+EXPORT_SYMBOL_GPL(devfreq_event_enable_edev);
+
+/**
+ * devfreq_event_disable_edev() - Disable the devfreq-event dev and decrease
+ *                                the enable_count of the devfreq-event dev.
+ * @edev        : the devfreq-event device
+ *
+ * Note that this function decrease the enable_count and disable the
+ * devfreq-event device. After the devfreq-event device is disabled,
+ * devfreq device can't use the devfreq-event device for get/set/reset
+ * operations.
+ */
+int devfreq_event_disable_edev(struct devfreq_event_dev *edev)
+{
+        int ret = 0;
+
+        if (!edev || !edev->desc)
+                return -EINVAL;
+
+        mutex_lock(&edev->lock);
+        if (edev->enable_count <= 0) {
+                dev_warn(&edev->dev, "unbalanced enable_count\n");
+                ret = -EIO;
+                goto err;
+        }
+
+        if (edev->desc->ops && edev->desc->ops->disable
+                        && edev->enable_count == 1) {
+                ret = edev->desc->ops->disable(edev);
+                if (ret < 0)
+                        goto err;
+        }
+        edev->enable_count--;
+err:
+        mutex_unlock(&edev->lock);
+
+        return ret;
+}
+EXPORT_SYMBOL_GPL(devfreq_event_disable_edev);
+
+/**
+ * devfreq_event_is_enabled() - Check whether devfreq-event dev is enabled or
+ *                              not.
+ * @edev        : the devfreq-event device
+ *
+ * Note that this function check whether devfreq-event dev is enabled or not.
+ * If return true, the devfreq-event dev is enabeld. If return false, the
+ * devfreq-event dev is disabled.
+ */
+bool devfreq_event_is_enabled(struct devfreq_event_dev *edev)
+{
+        bool enabled = false;
+
+        if (!edev || !edev->desc)
+                return enabled;
+
+        mutex_lock(&edev->lock);
+
+        if (edev->enable_count > 0)
+                enabled = true;
+
+        mutex_unlock(&edev->lock);
+
+        return enabled;
+}
+EXPORT_SYMBOL_GPL(devfreq_event_is_enabled);
+
+/**
+ * devfreq_event_set_event() - Set event to devfreq-event dev to start.
+ * @edev        : the devfreq-event device
+ *
+ * Note that this function set the event to the devfreq-event device to start
+ * for getting the event data which could be various event type.
+ */
+int devfreq_event_set_event(struct devfreq_event_dev *edev)
+{
+        int ret;
+
+        if (!edev || !edev->desc)
+                return -EINVAL;
+
+        if (!edev->desc->ops || !edev->desc->ops->set_event)
+                return -EINVAL;
+
+        if (!devfreq_event_is_enabled(edev))
+                return -EPERM;
+
+        mutex_lock(&edev->lock);
+        ret = edev->desc->ops->set_event(edev);
+        mutex_unlock(&edev->lock);
+
+        return ret;
+}
+EXPORT_SYMBOL_GPL(devfreq_event_set_event);
+
+/**
+ * devfreq_event_get_event() - Get {load|total}_count from devfreq-event dev.
+ * @edev        : the devfreq-event device
+ * @edata       : the calculated data of devfreq-event device
+ *
+ * Note that this function get the calculated event data from devfreq-event dev
+ * after stoping the progress of whole sequence of devfreq-event dev.
+ */
+int devfreq_event_get_event(struct devfreq_event_dev *edev,
+                            struct devfreq_event_data *edata)
+{
+        int ret;
+
+        if (!edev || !edev->desc)
+                return -EINVAL;
+
+        if (!edev->desc->ops || !edev->desc->ops->get_event)
+                return -EINVAL;
+
+        if (!devfreq_event_is_enabled(edev))
+                return -EINVAL;
+
+        edata->total_count = edata->load_count = 0;
+
+        mutex_lock(&edev->lock);
+        ret = edev->desc->ops->get_event(edev, edata);
+        if (ret < 0)
+                edata->total_count = edata->load_count = 0;
+        mutex_unlock(&edev->lock);
+
+        return ret;
+}
+EXPORT_SYMBOL_GPL(devfreq_event_get_event);
+
+/**
+ * devfreq_event_reset_event() - Reset all opeations of devfreq-event dev.
+ * @edev        : the devfreq-event device
+ *
+ * Note that this function stop all operations of devfreq-event dev and reset
+ * the current event data to make the devfreq-event device into initial state.
+ */
+int devfreq_event_reset_event(struct devfreq_event_dev *edev)
+{
+        int ret = 0;
+
+        if (!edev || !edev->desc)
+                return -EINVAL;
+
+        if (!devfreq_event_is_enabled(edev))
+                return -EPERM;
+
+        mutex_lock(&edev->lock);
+        if (edev->desc->ops && edev->desc->ops->reset)
+                ret = edev->desc->ops->reset(edev);
+        mutex_unlock(&edev->lock);
+
+        return ret;
+}
+EXPORT_SYMBOL_GPL(devfreq_event_reset_event);
+
+/**
+ * devfreq_event_get_edev_by_phandle() - Get the devfreq-event dev from
+ *                                       devicetree.
+ * @dev         : the pointer to the given device
+ * @index       : the index into list of devfreq-event device
+ *
+ * Note that this function return the pointer of devfreq-event device.
+ */
+struct devfreq_event_dev *devfreq_event_get_edev_by_phandle(struct device *dev,
+                                                      int index)
+{
+        struct device_node *node;
+        struct devfreq_event_dev *edev;
+
+        if (!dev->of_node) {
+                dev_err(dev, "device does not have a device node entry\n");
+                return ERR_PTR(-EINVAL);
+        }
+
+        node = of_parse_phandle(dev->of_node, "devfreq-events", index);
+        if (!node) {
+                dev_err(dev, "failed to get phandle in %s node\n",
+                        dev->of_node->full_name);
+                return ERR_PTR(-ENODEV);
+        }
+
+        mutex_lock(&devfreq_event_list_lock);
+        list_for_each_entry(edev, &devfreq_event_list, node) {
+                if (!strcmp(edev->desc->name, node->name))
+                        goto out;
+        }
+        edev = NULL;
+out:
+        mutex_unlock(&devfreq_event_list_lock);
+
+        if (!edev) {
+                dev_err(dev, "unable to get devfreq-event device : %s\n",
+                        node->name);
+                of_node_put(node);
+                return ERR_PTR(-ENODEV);
+        }
+
+        of_node_put(node);
+
+        return edev;
+}
+EXPORT_SYMBOL_GPL(devfreq_event_get_edev_by_phandle);
+
+/**
+ * devfreq_event_get_edev_count() - Get the count of devfreq-event dev
+ * @dev         : the pointer to the given device
+ *
+ * Note that this function return the count of devfreq-event devices.
+ */
+int devfreq_event_get_edev_count(struct device *dev)
+{
+        int count;
+
+        if (!dev->of_node) {
+                dev_err(dev, "device does not have a device node entry\n");
+                return -EINVAL;
+        }
+
+        count = of_property_count_elems_of_size(dev->of_node, "devfreq-events",
+                                                sizeof(u32));
+        if (count < 0 ) {
+                dev_err(dev,
+                        "failed to get the count of devfreq-event in %s node\n",
+                        dev->of_node->full_name);
+                return count;
+        }
+
+        return count;
+}
+EXPORT_SYMBOL_GPL(devfreq_event_get_edev_count);
+
+static void devfreq_event_release_edev(struct device *dev)
+{
+        struct devfreq_event_dev *edev = to_devfreq_event(dev);
+
+        kfree(edev);
+}
+
+/**
+ * devfreq_event_add_edev() - Add new devfreq-event device.
+ * @dev         : the device owning the devfreq-event device being created
+ * @desc        : the devfreq-event device's decriptor which include essential
+ *                data for devfreq-event device.
+ *
+ * Note that this function add new devfreq-event device to devfreq-event class
+ * list and register the device of the devfreq-event device.
+ */
+struct devfreq_event_dev *devfreq_event_add_edev(struct device *dev,
+                                                struct devfreq_event_desc *desc)
+{
+        struct devfreq_event_dev *edev;
+        static atomic_t event_no = ATOMIC_INIT(0);
+        int ret;
+
+        if (!dev || !desc)
+                return ERR_PTR(-EINVAL);
+
+        if (!desc->name || !desc->ops)
+                return ERR_PTR(-EINVAL);
+
+        if (!desc->ops->set_event || !desc->ops->get_event)
+                return ERR_PTR(-EINVAL);
+
+        edev = kzalloc(sizeof(struct devfreq_event_dev), GFP_KERNEL);
+        if (!edev)
+                return ERR_PTR(-ENOMEM);
+
+        mutex_init(&edev->lock);
+        edev->desc = desc;
+        edev->enable_count = 0;
+        edev->dev.parent = dev;
+        edev->dev.class = devfreq_event_class;
+        edev->dev.release = devfreq_event_release_edev;
+
+        dev_set_name(&edev->dev, "event.%d", atomic_inc_return(&event_no) - 1);
+        ret = device_register(&edev->dev);
+        if (ret < 0) {
+                put_device(&edev->dev);
+                return ERR_PTR(ret);
+        }
+        dev_set_drvdata(&edev->dev, edev);
+
+        INIT_LIST_HEAD(&edev->node);
+
+        mutex_lock(&devfreq_event_list_lock);
+        list_add(&edev->node, &devfreq_event_list);
+        mutex_unlock(&devfreq_event_list_lock);
+
+        return edev;
+}
+EXPORT_SYMBOL_GPL(devfreq_event_add_edev);
+
+/**
+ * devfreq_event_remove_edev() - Remove the devfreq-event device registered.
+ * @dev         : the devfreq-event device
+ *
+ * Note that this function remove the registered devfreq-event device.
+ */
+int devfreq_event_remove_edev(struct devfreq_event_dev *edev)
+{
+        if (!edev)
+                return -EINVAL;
+
+        WARN_ON(edev->enable_count);
+
+        mutex_lock(&devfreq_event_list_lock);
+        list_del(&edev->node);
+        mutex_unlock(&devfreq_event_list_lock);
+
+        device_unregister(&edev->dev);
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(devfreq_event_remove_edev);
+
+static int devm_devfreq_event_match(struct device *dev, void *res, void *data)
+{
+        struct devfreq_event_dev **r = res;
+
+        if (WARN_ON(!r || !*r))
+                return 0;
+
+        return *r == data;
+}
+
+static void devm_devfreq_event_release(struct device *dev, void *res)
+{
+        devfreq_event_remove_edev(*(struct devfreq_event_dev **)res);
+}
+
+/**
+ * devm_devfreq_event_add_edev() - Resource-managed devfreq_event_add_edev()
+ * @dev         : the device owning the devfreq-event device being created
+ * @desc        : the devfreq-event device's decriptor which include essential
+ *                data for devfreq-event device.
+ *
+ * Note that this function manages automatically the memory of devfreq-event
+ * device using device resource management and simplify the free operation
+ * for memory of devfreq-event device.
+ */
+struct devfreq_event_dev *devm_devfreq_event_add_edev(struct device *dev,
+                                                struct devfreq_event_desc *desc)
+{
+        struct devfreq_event_dev **ptr, *edev;
+
+        ptr = devres_alloc(devm_devfreq_event_release, sizeof(*ptr), GFP_KERNEL);
+        if (!ptr)
+                return ERR_PTR(-ENOMEM);
+
+        edev = devfreq_event_add_edev(dev, desc);
+        if (IS_ERR(edev)) {
+                devres_free(ptr);
+                return ERR_PTR(-ENOMEM);
+        }
+
+        *ptr = edev;
+        devres_add(dev, ptr);
+
+        return edev;
+}
+EXPORT_SYMBOL_GPL(devm_devfreq_event_add_edev);
+
+/**
+ * devm_devfreq_event_remove_edev()- Resource-managed devfreq_event_remove_edev()
+ * @dev         : the device owning the devfreq-event device being created
+ * @edev        : the devfreq-event device
+ *
+ * Note that this function manages automatically the memory of devfreq-event
+ * device using device resource management.
+ */
+void devm_devfreq_event_remove_edev(struct device *dev,
+                                struct devfreq_event_dev *edev)
+{
+        WARN_ON(devres_release(dev, devm_devfreq_event_release,
+                               devm_devfreq_event_match, edev));
+}
+EXPORT_SYMBOL_GPL(devm_devfreq_event_remove_edev);
+
+/*
+ * Device attributes for devfreq-event class.
+ */
+static ssize_t name_show(struct device *dev, struct device_attribute *attr,
+                         char *buf)
+{
+        struct devfreq_event_dev *edev = to_devfreq_event(dev);
+
+        if (!edev || !edev->desc)
+                return -EINVAL;
+
+        return sprintf(buf, "%s\n", edev->desc->name);
+}
+static DEVICE_ATTR_RO(name);
+
+static ssize_t enable_count_show(struct device *dev,
+                                  struct device_attribute *attr, char *buf)
+{
+        struct devfreq_event_dev *edev = to_devfreq_event(dev);
+
+        if (!edev || !edev->desc)
+                return -EINVAL;
+
+        return sprintf(buf, "%d\n", edev->enable_count);
+}
+static DEVICE_ATTR_RO(enable_count);
+
+static struct attribute *devfreq_event_attrs[] = {
+        &dev_attr_name.attr,
+        &dev_attr_enable_count.attr,
+        NULL,
+};
+ATTRIBUTE_GROUPS(devfreq_event);
+
+static int __init devfreq_event_init(void)
+{
+        devfreq_event_class = class_create(THIS_MODULE, "devfreq-event");
+        if (IS_ERR(devfreq_event_class)) {
+                pr_err("%s: couldn't create class\n", __FILE__);
+                return PTR_ERR(devfreq_event_class);
+        }
+
+        devfreq_event_class->dev_groups = devfreq_event_groups;
+
+        return 0;
+}
+subsys_initcall(devfreq_event_init);
+
+static void __exit devfreq_event_exit(void)
+{
+        class_destroy(devfreq_event_class);
+}
+module_exit(devfreq_event_exit);
+
+MODULE_AUTHOR("Chanwoo Choi <cw00.choi@samsung.com>");
+MODULE_DESCRIPTION("DEVFREQ-Event class support");
+MODULE_LICENSE("GPL");