--- /dev/null
+PM quality of Service interface.
+
+This interface provides a kernel and user mode interface for registering
+performance expectations by drivers, subsystems and user space applications on
+one of the parameters.
+
+Currently we have {cpu_dma_latency, network_latency, network_throughput} as the
+initial set of pm_qos parameters.
+
+The infrastructure exposes multiple misc device nodes one per implemented
+parameter. The set of parameters implement is defined by pm_qos_power_init()
+and pm_qos_params.h. This is done because having the available parameters
+being runtime configurable or changeable from a driver was seen as too easy to
+abuse.
+
+For each parameter a list of performance requirements is maintained along with
+an aggregated target value. The aggregated target value is updated with
+changes to the requirement list or elements of the list. Typically the
+aggregated target value is simply the max or min of the requirement values held
+in the parameter list elements.
+
+From kernel mode the use of this interface is simple:
+pm_qos_add_requirement(param_id, name, target_value):
+Will insert a named element in the list for that identified PM_QOS parameter
+with the target value. Upon change to this list the new target is recomputed
+and any registered notifiers are called only if the target value is now
+different.
+
+pm_qos_update_requirement(param_id, name, new_target_value):
+Will search the list identified by the param_id for the named list element and
+then update its target value, calling the notification tree if the aggregated
+target is changed. with that name is already registered.
+
+pm_qos_remove_requirement(param_id, name):
+Will search the identified list for the named element and remove it, after
+removal it will update the aggregate target and call the notification tree if
+the target was changed as a result of removing the named requirement.
+
+
+From user mode:
+Only processes can register a pm_qos requirement. To provide for automatic
+cleanup for process the interface requires the process to register its
+parameter requirements in the following way:
+
+To register the default pm_qos target for the specific parameter, the process
+must open one of /dev/[cpu_dma_latency, network_latency, network_throughput]
+
+As long as the device node is held open that process has a registered
+requirement on the parameter. The name of the requirement is "process_<PID>"
+derived from the current->pid from within the open system call.
+
+To change the requested target value the process needs to write a s32 value to
+the open device node. This translates to a pm_qos_update_requirement call.
+
+To remove the user mode request for a target value simply close the device
+node.
+
+
+
--- /dev/null
+/*
+ * 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/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 target_value or 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;
+ s32 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 = 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 = 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 = 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 (pm_qos_array[target]->target_value != extreme_value) {
+ call_notifier = 1;
+ pm_qos_array[target]->target_value = extreme_value;
+ pr_debug(KERN_ERR "new target for qos %d is %d\n", target,
+ 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)
+{
+ int ret_val;
+ unsigned long flags;
+
+ spin_lock_irqsave(&pm_qos_lock, flags);
+ ret_val = pm_qos_array[pm_qos_class]->target_value;
+ spin_unlock_irqrestore(&pm_qos_lock, flags);
+
+ return ret_val;
+}
+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 charactoistics. It recomputes the agregate QoS expectations for
+ * the pm_qos_class of parrameters.
+ */
+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 requierement for the pm_qos_class of parameters along
+ * with updating the target pm_qos_class value.
+ *
+ * If the named request isn't in the lest 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 parrameters 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
+ * uppon 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
+ * uppon 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;
+
+ 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)
+ return 0;
+ }
+
+ 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);
projects / linux-2.6 / commitdiff