/*
 * This module exposes the interface to kernel space for specifying
 * QoS dependencies.  It provides infrastructure for registration of:
 *
 * Dependents on a QoS value : register requirements
 * Watchers of QoS value : get notified when target QoS value changes
 *
 * This QoS design is best effort based.  Dependents register their QoS needs.
 * Watchers register to keep track of the current QoS needs of the system.
 *
 * There are 3 basic classes of QoS parameter: latency, timeout, throughput
 * each have defined units:
 * latency: usec
 * timeout: usec <-- currently not used.
 * throughput: kbs (kilo byte / sec)
 *
 * There are lists of pm_qos_objects each one wrapping requirements, notifiers
 *
 * User mode requirements on a QOS parameter register themselves to the
 * subsystem by opening the device node /dev/... and writing there request to
 * the node.  As long as the process holds a file handle open to the node the
 * client continues to be accounted for.  Upon file release the usermode
 * requirement is removed and a new qos target is computed.  This way when the
 * requirement that the application has is cleaned up when closes the file
 * pointer or exits the pm_qos_object will get an opportunity to clean up.
 *
 * Mark Gross <mgross@linux.intel.com>
 */

#include <linux/pm_qos_params.h>
#include <linux/sched.h>
#include <linux/smp_lock.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/time.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/miscdevice.h>
#include <linux/string.h>
#include <linux/platform_device.h>
#include <linux/init.h>

#include <linux/uaccess.h>

/*
 * locking rule: all changes to requirements or notifiers lists
 * or pm_qos_object list and pm_qos_objects need to happen with pm_qos_lock
 * held, taken with _irqsave.  One lock to rule them all
 */
struct requirement_list {
        struct list_head list;
        union {
                s32 value;
                s32 usec;
                s32 kbps;
        };
        char *name;
};

static s32 max_compare(s32 v1, s32 v2);
static s32 min_compare(s32 v1, s32 v2);

struct pm_qos_object {
        struct requirement_list requirements;
        struct blocking_notifier_head *notifiers;
        struct miscdevice pm_qos_power_miscdev;
        char *name;
        s32 default_value;
        atomic_t target_value;
        s32 (*comparitor)(s32, s32);
};

static struct pm_qos_object null_pm_qos;
static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
static struct pm_qos_object cpu_dma_pm_qos = {
        .requirements = {LIST_HEAD_INIT(cpu_dma_pm_qos.requirements.list)},
        .notifiers = &cpu_dma_lat_notifier,
        .name = "cpu_dma_latency",
        .default_value = 2000 * USEC_PER_SEC,
        .target_value = ATOMIC_INIT(2000 * USEC_PER_SEC),
        .comparitor = min_compare
};

static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
static struct pm_qos_object network_lat_pm_qos = {
        .requirements = {LIST_HEAD_INIT(network_lat_pm_qos.requirements.list)},
        .notifiers = &network_lat_notifier,
        .name = "network_latency",
        .default_value = 2000 * USEC_PER_SEC,
        .target_value = ATOMIC_INIT(2000 * USEC_PER_SEC),
        .comparitor = min_compare
};


static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
static struct pm_qos_object network_throughput_pm_qos = {
        .requirements =
                {LIST_HEAD_INIT(network_throughput_pm_qos.requirements.list)},
        .notifiers = &network_throughput_notifier,
        .name = "network_throughput",
        .default_value = 0,
        .target_value = ATOMIC_INIT(0),
        .comparitor = max_compare
};


static struct pm_qos_object *pm_qos_array[] = {
        &null_pm_qos,
        &cpu_dma_pm_qos,
        &network_lat_pm_qos,
        &network_throughput_pm_qos
};

static DEFINE_SPINLOCK(pm_qos_lock);

static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
                size_t count, loff_t *f_pos);
static int pm_qos_power_open(struct inode *inode, struct file *filp);
static int pm_qos_power_release(struct inode *inode, struct file *filp);

static const struct file_operations pm_qos_power_fops = {
        .write = pm_qos_power_write,
        .open = pm_qos_power_open,
        .release = pm_qos_power_release,
};

/* static helper functions */
static s32 max_compare(s32 v1, s32 v2)
{
        return max(v1, v2);
}

static s32 min_compare(s32 v1, s32 v2)
{
        return min(v1, v2);
}


static void update_target(int target)
{
        s32 extreme_value;
        struct requirement_list *node;
        unsigned long flags;
        int call_notifier = 0;

        spin_lock_irqsave(&pm_qos_lock, flags);
        extreme_value = pm_qos_array[target]->default_value;
        list_for_each_entry(node,
                        &pm_qos_array[target]->requirements.list, list) {
                extreme_value = pm_qos_array[target]->comparitor(
                                extreme_value, node->value);
        }
        if (atomic_read(&pm_qos_array[target]->target_value) != extreme_value) {
                call_notifier = 1;
                atomic_set(&pm_qos_array[target]->target_value, extreme_value);
                pr_debug(KERN_ERR "new target for qos %d is %d\n", target,
                        atomic_read(&pm_qos_array[target]->target_value));
        }
        spin_unlock_irqrestore(&pm_qos_lock, flags);

        if (call_notifier)
                blocking_notifier_call_chain(pm_qos_array[target]->notifiers,
                        (unsigned long) extreme_value, NULL);
}

static int register_pm_qos_misc(struct pm_qos_object *qos)
{
        qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
        qos->pm_qos_power_miscdev.name = qos->name;
        qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;

        return misc_register(&qos->pm_qos_power_miscdev);
}

static int find_pm_qos_object_by_minor(int minor)
{
        int pm_qos_class;

        for (pm_qos_class = 0;
                pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
                if (minor ==
                        pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
                        return pm_qos_class;
        }
        return -1;
}

/**
 * pm_qos_requirement - returns current system wide qos expectation
 * @pm_qos_class: identification of which qos value is requested
 *
 * This function returns the current target value in an atomic manner.
 */
int pm_qos_requirement(int pm_qos_class)
{
        return atomic_read(&pm_qos_array[pm_qos_class]->target_value);
}
EXPORT_SYMBOL_GPL(pm_qos_requirement);

/**
 * pm_qos_add_requirement - inserts new qos request into the list
 * @pm_qos_class: identifies which list of qos request to us
 * @name: identifies the request
 * @value: defines the qos request
 *
 * This function inserts a new entry in the pm_qos_class list of requested qos
 * performance characteristics.  It recomputes the aggregate QoS expectations
 * for the pm_qos_class of parameters.
 */
int pm_qos_add_requirement(int pm_qos_class, char *name, s32 value)
{
        struct requirement_list *dep;
        unsigned long flags;

        dep = kzalloc(sizeof(struct requirement_list), GFP_KERNEL);
        if (dep) {
                if (value == PM_QOS_DEFAULT_VALUE)
                        dep->value = pm_qos_array[pm_qos_class]->default_value;
                else
                        dep->value = value;
                dep->name = kstrdup(name, GFP_KERNEL);
                if (!dep->name)
                        goto cleanup;

                spin_lock_irqsave(&pm_qos_lock, flags);
                list_add(&dep->list,
                        &pm_qos_array[pm_qos_class]->requirements.list);
                spin_unlock_irqrestore(&pm_qos_lock, flags);
                update_target(pm_qos_class);

                return 0;
        }

cleanup:
        kfree(dep);
        return -ENOMEM;
}
EXPORT_SYMBOL_GPL(pm_qos_add_requirement);

/**
 * pm_qos_update_requirement - modifies an existing qos request
 * @pm_qos_class: identifies which list of qos request to us
 * @name: identifies the request
 * @value: defines the qos request
 *
 * Updates an existing qos requirement for the pm_qos_class of parameters along
 * with updating the target pm_qos_class value.
 *
 * If the named request isn't in the list then no change is made.
 */
int pm_qos_update_requirement(int pm_qos_class, char *name, s32 new_value)
{
        unsigned long flags;
        struct requirement_list *node;
        int pending_update = 0;

        spin_lock_irqsave(&pm_qos_lock, flags);
        list_for_each_entry(node,
                &pm_qos_array[pm_qos_class]->requirements.list, list) {
                if (strcmp(node->name, name) == 0) {
                        if (new_value == PM_QOS_DEFAULT_VALUE)
                                node->value =
                                pm_qos_array[pm_qos_class]->default_value;
                        else
                                node->value = new_value;
                        pending_update = 1;
                        break;
                }
        }
        spin_unlock_irqrestore(&pm_qos_lock, flags);
        if (pending_update)
                update_target(pm_qos_class);

        return 0;
}
EXPORT_SYMBOL_GPL(pm_qos_update_requirement);

/**
 * pm_qos_remove_requirement - modifies an existing qos request
 * @pm_qos_class: identifies which list of qos request to us
 * @name: identifies the request
 *
 * Will remove named qos request from pm_qos_class list of parameters and
 * recompute the current target value for the pm_qos_class.
 */
void pm_qos_remove_requirement(int pm_qos_class, char *name)
{
        unsigned long flags;
        struct requirement_list *node;
        int pending_update = 0;

        spin_lock_irqsave(&pm_qos_lock, flags);
        list_for_each_entry(node,
                &pm_qos_array[pm_qos_class]->requirements.list, list) {
                if (strcmp(node->name, name) == 0) {
                        kfree(node->name);
                        list_del(&node->list);
                        kfree(node);
                        pending_update = 1;
                        break;
                }
        }
        spin_unlock_irqrestore(&pm_qos_lock, flags);
        if (pending_update)
                update_target(pm_qos_class);
}
EXPORT_SYMBOL_GPL(pm_qos_remove_requirement);

/**
 * pm_qos_add_notifier - sets notification entry for changes to target value
 * @pm_qos_class: identifies which qos target changes should be notified.
 * @notifier: notifier block managed by caller.
 *
 * will register the notifier into a notification chain that gets called
 * upon changes to the pm_qos_class target value.
 */
 int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
{
        int retval;

        retval = blocking_notifier_chain_register(
                        pm_qos_array[pm_qos_class]->notifiers, notifier);

        return retval;
}
EXPORT_SYMBOL_GPL(pm_qos_add_notifier);

/**
 * pm_qos_remove_notifier - deletes notification entry from chain.
 * @pm_qos_class: identifies which qos target changes are notified.
 * @notifier: notifier block to be removed.
 *
 * will remove the notifier from the notification chain that gets called
 * upon changes to the pm_qos_class target value.
 */
int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
{
        int retval;

        retval = blocking_notifier_chain_unregister(
                        pm_qos_array[pm_qos_class]->notifiers, notifier);

        return retval;
}
EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);

#define PID_NAME_LEN sizeof("process_1234567890")
static char name[PID_NAME_LEN];

static int pm_qos_power_open(struct inode *inode, struct file *filp)
{
        int ret;
        long pm_qos_class;

        lock_kernel();
        pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
        if (pm_qos_class >= 0) {
                filp->private_data = (void *)pm_qos_class;
                sprintf(name, "process_%d", current->pid);
                ret = pm_qos_add_requirement(pm_qos_class, name,
                                        PM_QOS_DEFAULT_VALUE);
                if (ret >= 0) {
                        unlock_kernel();
                        return 0;
                }
        }
        unlock_kernel();

        return -EPERM;
}

static int pm_qos_power_release(struct inode *inode, struct file *filp)
{
        int pm_qos_class;

        pm_qos_class = (long)filp->private_data;
        sprintf(name, "process_%d", current->pid);
        pm_qos_remove_requirement(pm_qos_class, name);

        return 0;
}

static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
                size_t count, loff_t *f_pos)
{
        s32 value;
        int pm_qos_class;

        pm_qos_class = (long)filp->private_data;
        if (count != sizeof(s32))
                return -EINVAL;
        if (copy_from_user(&value, buf, sizeof(s32)))
                return -EFAULT;
        sprintf(name, "process_%d", current->pid);
        pm_qos_update_requirement(pm_qos_class, name, value);

        return  sizeof(s32);
}


static int __init pm_qos_power_init(void)
{
        int ret = 0;

        ret = register_pm_qos_misc(&cpu_dma_pm_qos);
        if (ret < 0) {
                printk(KERN_ERR "pm_qos_param: cpu_dma_latency setup failed\n");
                return ret;
        }
        ret = register_pm_qos_misc(&network_lat_pm_qos);
        if (ret < 0) {
                printk(KERN_ERR "pm_qos_param: network_latency setup failed\n");
                return ret;
        }
        ret = register_pm_qos_misc(&network_throughput_pm_qos);
        if (ret < 0)
                printk(KERN_ERR
                        "pm_qos_param: network_throughput setup failed\n");

        return ret;
}

late_initcall(pm_qos_power_init);