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DEFINITIONS
This source file includes following definitions.
- max_compare
- min_compare
- update_target
- register_pm_qos_misc
- find_pm_qos_object_by_minor
- pm_qos_requirement
- pm_qos_add_requirement
- pm_qos_update_requirement
- pm_qos_remove_requirement
- pm_qos_add_notifier
- pm_qos_remove_notifier
- pm_qos_power_open
- pm_qos_power_release
- pm_qos_power_write
- pm_qos_power_init
/*
* 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);