qos.c

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/*
 * This module exposes the interface to kernel space for specifying
 * QoS dependencies.  It provides infrastructure for registration of:
 *
 * Dependents on a QoS value : register requests
 * 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 requests, notifiers
 *
 * User mode requests 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
 * request is removed and a new qos target is computed.  This way when the
 * request 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 <[email protected]>
 */

/*#define DEBUG*/

#include <linux/pm_qos.h>
#include <linux/sched.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/kernel.h>

#include <linux/uaccess.h>
#include <linux/export.h>

/*
 * locking rule: all changes to constraints 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 pm_qos_object {
    struct pm_qos_constraints *constraints;
    struct miscdevice pm_qos_power_miscdev;
    char *name;
};

static DEFINE_SPINLOCK(pm_qos_lock);

static struct pm_qos_object null_pm_qos;

static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
static struct pm_qos_constraints cpu_dma_constraints = {
    .list = PLIST_HEAD_INIT(cpu_dma_constraints.list),
    .target_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE,
    .default_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE,
    .type = PM_QOS_MIN,
    .notifiers = &cpu_dma_lat_notifier,
};
static struct pm_qos_object cpu_dma_pm_qos = {
    .constraints = &cpu_dma_constraints,
    .name = "cpu_dma_latency",
};

static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
static struct pm_qos_constraints network_lat_constraints = {
    .list = PLIST_HEAD_INIT(network_lat_constraints.list),
    .target_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
    .default_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
    .type = PM_QOS_MIN,
    .notifiers = &network_lat_notifier,
};
static struct pm_qos_object network_lat_pm_qos = {
    .constraints = &network_lat_constraints,
    .name = "network_latency",
};


static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
static struct pm_qos_constraints network_tput_constraints = {
    .list = PLIST_HEAD_INIT(network_tput_constraints.list),
    .target_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
    .default_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
    .type = PM_QOS_MAX,
    .notifiers = &network_throughput_notifier,
};
static struct pm_qos_object network_throughput_pm_qos = {
    .constraints = &network_tput_constraints,
    .name = "network_throughput",
};


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

static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
        size_t count, loff_t *f_pos);
static ssize_t pm_qos_power_read(struct file *filp, 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,
    .read = pm_qos_power_read,
    .open = pm_qos_power_open,
    .release = pm_qos_power_release,
    .llseek = noop_llseek,
};

/* unlocked internal variant */
static inline int pm_qos_get_value(struct pm_qos_constraints *c)
{
    if (plist_head_empty(&c->list))
        return c->default_value;

    switch (c->type) {
    case PM_QOS_MIN:
        return plist_first(&c->list)->prio;

    case PM_QOS_MAX:
        return plist_last(&c->list)->prio;

    default:
        /* runtime check for not using enum */
        BUG();
        return PM_QOS_DEFAULT_VALUE;
    }
}

s32 pm_qos_read_value(struct pm_qos_constraints *c)
{
    return c->target_value;
}

static inline void pm_qos_set_value(struct pm_qos_constraints *c, s32 value)
{
    c->target_value = value;
}

int pm_qos_update_target(struct pm_qos_constraints *c, struct plist_node *node,
             enum pm_qos_req_action action, int value)
{
    unsigned long flags;
    int prev_value, curr_value, new_value;

    spin_lock_irqsave(&pm_qos_lock, flags);
    prev_value = pm_qos_get_value(c);
    if (value == PM_QOS_DEFAULT_VALUE)
        new_value = c->default_value;
    else
        new_value = value;

    switch (action) {
    case PM_QOS_REMOVE_REQ:
        plist_del(node, &c->list);
        break;
    case PM_QOS_UPDATE_REQ:
        /*
         * to change the list, we atomically remove, reinit
         * with new value and add, then see if the extremal
         * changed
         */
        plist_del(node, &c->list);
    case PM_QOS_ADD_REQ:
        plist_node_init(node, new_value);
        plist_add(node, &c->list);
        break;
    default:
        /* no action */
        ;
    }

    curr_value = pm_qos_get_value(c);
    pm_qos_set_value(c, curr_value);

    spin_unlock_irqrestore(&pm_qos_lock, flags);

    if (prev_value != curr_value) {
        blocking_notifier_call_chain(c->notifiers,
                         (unsigned long)curr_value,
                         NULL);
        return 1;
    } else {
        return 0;
    }
}

int pm_qos_request(int pm_qos_class)
{
    return pm_qos_read_value(pm_qos_array[pm_qos_class]->constraints);
}
EXPORT_SYMBOL_GPL(pm_qos_request);

int pm_qos_request_active(struct pm_qos_request *req)
{
    return req->pm_qos_class != 0;
}
EXPORT_SYMBOL_GPL(pm_qos_request_active);

static void pm_qos_work_fn(struct work_struct *work)
{
    struct pm_qos_request *req = container_of(to_delayed_work(work),
                          struct pm_qos_request,
                          work);

    pm_qos_update_request(req, PM_QOS_DEFAULT_VALUE);
}

void pm_qos_add_request(struct pm_qos_request *req,
            int pm_qos_class, s32 value)
{
    if (!req) /*guard against callers passing in null */
        return;

    if (pm_qos_request_active(req)) {
        WARN(1, KERN_ERR "pm_qos_add_request() called for already added request\n");
        return;
    }
    req->pm_qos_class = pm_qos_class;
    INIT_DELAYED_WORK(&req->work, pm_qos_work_fn);
    pm_qos_update_target(pm_qos_array[pm_qos_class]->constraints,
                 &req->node, PM_QOS_ADD_REQ, value);
}
EXPORT_SYMBOL_GPL(pm_qos_add_request);

void pm_qos_update_request(struct pm_qos_request *req,
               s32 new_value)
{
    if (!req) /*guard against callers passing in null */
        return;

    if (!pm_qos_request_active(req)) {
        WARN(1, KERN_ERR "pm_qos_update_request() called for unknown object\n");
        return;
    }

    if (delayed_work_pending(&req->work))
        cancel_delayed_work_sync(&req->work);

    if (new_value != req->node.prio)
        pm_qos_update_target(
            pm_qos_array[req->pm_qos_class]->constraints,
            &req->node, PM_QOS_UPDATE_REQ, new_value);
}
EXPORT_SYMBOL_GPL(pm_qos_update_request);

void pm_qos_update_request_timeout(struct pm_qos_request *req, s32 new_value,
                   unsigned long timeout_us)
{
    if (!req)
        return;
    if (WARN(!pm_qos_request_active(req),
         "%s called for unknown object.", __func__))
        return;

    if (delayed_work_pending(&req->work))
        cancel_delayed_work_sync(&req->work);

    if (new_value != req->node.prio)
        pm_qos_update_target(
            pm_qos_array[req->pm_qos_class]->constraints,
            &req->node, PM_QOS_UPDATE_REQ, new_value);

    schedule_delayed_work(&req->work, usecs_to_jiffies(timeout_us));
}

void pm_qos_remove_request(struct pm_qos_request *req)
{
    if (!req) /*guard against callers passing in null */
        return;
        /* silent return to keep pcm code cleaner */

    if (!pm_qos_request_active(req)) {
        WARN(1, KERN_ERR "pm_qos_remove_request() called for unknown object\n");
        return;
    }

    if (delayed_work_pending(&req->work))
        cancel_delayed_work_sync(&req->work);

    pm_qos_update_target(pm_qos_array[req->pm_qos_class]->constraints,
                 &req->node, PM_QOS_REMOVE_REQ,
                 PM_QOS_DEFAULT_VALUE);
    memset(req, 0, sizeof(*req));
}
EXPORT_SYMBOL_GPL(pm_qos_remove_request);

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]->constraints->notifiers,
            notifier);

    return retval;
}
EXPORT_SYMBOL_GPL(pm_qos_add_notifier);

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]->constraints->notifiers,
            notifier);

    return retval;
}
EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);

/* User space interface to PM QoS classes via misc devices */
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;
}

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

    pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
    if (pm_qos_class >= 0) {
        struct pm_qos_request *req = kzalloc(sizeof(*req), GFP_KERNEL);
        if (!req)
            return -ENOMEM;

        pm_qos_add_request(req, pm_qos_class, PM_QOS_DEFAULT_VALUE);
        filp->private_data = req;

        return 0;
    }
    return -EPERM;
}

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

    req = filp->private_data;
    pm_qos_remove_request(req);
    kfree(req);

    return 0;
}


static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
        size_t count, loff_t *f_pos)
{
    s32 value;
    unsigned long flags;
    struct pm_qos_request *req = filp->private_data;

    if (!req)
        return -EINVAL;
    if (!pm_qos_request_active(req))
        return -EINVAL;

    spin_lock_irqsave(&pm_qos_lock, flags);
    value = pm_qos_get_value(pm_qos_array[req->pm_qos_class]->constraints);
    spin_unlock_irqrestore(&pm_qos_lock, flags);

    return simple_read_from_buffer(buf, count, f_pos, &value, sizeof(s32));
}

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

    if (count == sizeof(s32)) {
        if (copy_from_user(&value, buf, sizeof(s32)))
            return -EFAULT;
    } else if (count <= 11) { /* ASCII perhaps? */
        char ascii_value[11];
        unsigned long int ulval;
        int ret;

        if (copy_from_user(ascii_value, buf, count))
            return -EFAULT;

        if (count > 10) {
            if (ascii_value[10] == '\n')
                ascii_value[10] = '\0';
            else
                return -EINVAL;
        } else {
            ascii_value[count] = '\0';
        }
        ret = strict_strtoul(ascii_value, 16, &ulval);
        if (ret) {
            pr_debug("%s, 0x%lx, 0x%x\n", ascii_value, ulval, ret);
            return -EINVAL;
        }
        value = (s32)lower_32_bits(ulval);
    } else {
        return -EINVAL;
    }

    req = filp->private_data;
    pm_qos_update_request(req, value);

    return count;
}


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

    BUILD_BUG_ON(ARRAY_SIZE(pm_qos_array) != PM_QOS_NUM_CLASSES);

    for (i = 1; i < PM_QOS_NUM_CLASSES; i++) {
        ret = register_pm_qos_misc(pm_qos_array[i]);
        if (ret < 0) {
            printk(KERN_ERR "pm_qos_param: %s setup failed\n",
                   pm_qos_array[i]->name);
            return ret;
        }
    }

    return ret;
}

late_initcall(pm_qos_power_init);