FreeBSD/Linux Kernel Cross Reference
sys/kernel/pm_qos_params.c

     /*
      * 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 <mgross@linux.intel.com>
     */
    
    /*#define DEBUG*/
    
    #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/kernel.h>
    
    #include <linux/uaccess.h>
    
    /*
     * locking rule: all changes to requests 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
     */
    enum pm_qos_type {
            PM_QOS_MAX,             /* return the largest value */
            PM_QOS_MIN              /* return the smallest value */
    };
    
    /*
     * Note: The lockless read path depends on the CPU accessing
     * target_value atomically.  Atomic access is only guaranteed on all CPU
     * types linux supports for 32 bit quantites
     */
    struct pm_qos_object {
            struct plist_head requests;
            struct blocking_notifier_head *notifiers;
            struct miscdevice pm_qos_power_miscdev;
            char *name;
            s32 target_value;       /* Do not change to 64 bit */
            s32 default_value;
            enum pm_qos_type type;
    };
    
    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_object cpu_dma_pm_qos = {
            .requests = PLIST_HEAD_INIT(cpu_dma_pm_qos.requests),
            .notifiers = &cpu_dma_lat_notifier,
            .name = "cpu_dma_latency",
            .target_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE,
            .default_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE,
            .type = PM_QOS_MIN,
    };
    
    static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
    static struct pm_qos_object network_lat_pm_qos = {
            .requests = PLIST_HEAD_INIT(network_lat_pm_qos.requests),
            .notifiers = &network_lat_notifier,
            .name = "network_latency",
            .target_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
            .default_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
            .type = PM_QOS_MIN
    };
    
    
    static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
    static struct pm_qos_object network_throughput_pm_qos = {
            .requests = PLIST_HEAD_INIT(network_throughput_pm_qos.requests),
            .notifiers = &network_throughput_notifier,
           .name = "network_throughput",
           .target_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
           .default_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
           .type = PM_QOS_MAX,
   };
   
   
   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_object *o)
   {
           if (plist_head_empty(&o->requests))
                   return o->default_value;
   
           switch (o->type) {
           case PM_QOS_MIN:
                   return plist_first(&o->requests)->prio;
   
           case PM_QOS_MAX:
                   return plist_last(&o->requests)->prio;
   
           default:
                   /* runtime check for not using enum */
                   BUG();
           }
   }
   
   static inline s32 pm_qos_read_value(struct pm_qos_object *o)
   {
           return o->target_value;
   }
   
   static inline void pm_qos_set_value(struct pm_qos_object *o, s32 value)
   {
           o->target_value = value;
   }
   
   static void update_target(struct pm_qos_object *o, struct plist_node *node,
                             int del, int value)
   {
           unsigned long flags;
           int prev_value, curr_value;
   
           spin_lock_irqsave(&pm_qos_lock, flags);
           prev_value = pm_qos_get_value(o);
           /* PM_QOS_DEFAULT_VALUE is a signal that the value is unchanged */
           if (value != PM_QOS_DEFAULT_VALUE) {
                   /*
                    * to change the list, we atomically remove, reinit
                    * with new value and add, then see if the extremal
                    * changed
                    */
                   plist_del(node, &o->requests);
                   plist_node_init(node, value);
                   plist_add(node, &o->requests);
           } else if (del) {
                   plist_del(node, &o->requests);
           } else {
                   plist_add(node, &o->requests);
           }
           curr_value = pm_qos_get_value(o);
           pm_qos_set_value(o, curr_value);
           spin_unlock_irqrestore(&pm_qos_lock, flags);
   
           if (prev_value != curr_value)
                   blocking_notifier_call_chain(o->notifiers,
                                                (unsigned long)curr_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_request - returns current system wide qos expectation
    * @pm_qos_class: identification of which qos value is requested
    *
    * This function returns the current target value.
    */
   int pm_qos_request(int pm_qos_class)
   {
           return pm_qos_read_value(pm_qos_array[pm_qos_class]);
   }
   EXPORT_SYMBOL_GPL(pm_qos_request);
   
   int pm_qos_request_active(struct pm_qos_request_list *req)
   {
           return req->pm_qos_class != 0;
   }
   EXPORT_SYMBOL_GPL(pm_qos_request_active);
   
   /**
    * pm_qos_add_request - inserts new qos request into the list
    * @dep: pointer to a preallocated handle
    * @pm_qos_class: identifies which list of qos request to use
    * @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 and initializes the pm_qos_request_list
    * handle.  Caller needs to save this handle for later use in updates and
    * removal.
    */
   
   void pm_qos_add_request(struct pm_qos_request_list *dep,
                           int pm_qos_class, s32 value)
   {
           struct pm_qos_object *o =  pm_qos_array[pm_qos_class];
           int new_value;
   
           if (pm_qos_request_active(dep)) {
                   WARN(1, KERN_ERR "pm_qos_add_request() called for already added request\n");
                   return;
           }
           if (value == PM_QOS_DEFAULT_VALUE)
                   new_value = o->default_value;
           else
                   new_value = value;
           plist_node_init(&dep->list, new_value);
           dep->pm_qos_class = pm_qos_class;
           update_target(o, &dep->list, 0, PM_QOS_DEFAULT_VALUE);
   }
   EXPORT_SYMBOL_GPL(pm_qos_add_request);
   
   /**
    * pm_qos_update_request - modifies an existing qos request
    * @pm_qos_req : handle to list element holding a pm_qos request to use
    * @value: defines the qos request
    *
    * Updates an existing qos request for the pm_qos_class of parameters along
    * with updating the target pm_qos_class value.
    *
    * Attempts are made to make this code callable on hot code paths.
    */
   void pm_qos_update_request(struct pm_qos_request_list *pm_qos_req,
                              s32 new_value)
   {
           s32 temp;
           struct pm_qos_object *o;
   
           if (!pm_qos_req) /*guard against callers passing in null */
                   return;
   
           if (!pm_qos_request_active(pm_qos_req)) {
                   WARN(1, KERN_ERR "pm_qos_update_request() called for unknown object\n");
                   return;
           }
   
           o = pm_qos_array[pm_qos_req->pm_qos_class];
   
           if (new_value == PM_QOS_DEFAULT_VALUE)
                   temp = o->default_value;
           else
                   temp = new_value;
   
           if (temp != pm_qos_req->list.prio)
                   update_target(o, &pm_qos_req->list, 0, temp);
   }
   EXPORT_SYMBOL_GPL(pm_qos_update_request);
   
   /**
    * pm_qos_remove_request - modifies an existing qos request
    * @pm_qos_req: handle to request list element
    *
    * Will remove pm qos request from the list of requests and
    * recompute the current target value for the pm_qos_class.  Call this
    * on slow code paths.
    */
   void pm_qos_remove_request(struct pm_qos_request_list *pm_qos_req)
   {
           struct pm_qos_object *o;
   
           if (pm_qos_req == NULL)
                   return;
                   /* silent return to keep pcm code cleaner */
   
           if (!pm_qos_request_active(pm_qos_req)) {
                   WARN(1, KERN_ERR "pm_qos_remove_request() called for unknown object\n");
                   return;
           }
   
           o = pm_qos_array[pm_qos_req->pm_qos_class];
           update_target(o, &pm_qos_req->list, 1, PM_QOS_DEFAULT_VALUE);
           memset(pm_qos_req, 0, sizeof(*pm_qos_req));
   }
   EXPORT_SYMBOL_GPL(pm_qos_remove_request);
   
   /**
    * 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);
   
   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_list *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;
   
                   if (filp->private_data)
                           return 0;
           }
           return -EPERM;
   }
   
   static int pm_qos_power_release(struct inode *inode, struct file *filp)
   {
           struct pm_qos_request_list *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_object *o;
           struct pm_qos_request_list *pm_qos_req = filp->private_data;
   
           if (!pm_qos_req)
                   return -EINVAL;
           if (!pm_qos_request_active(pm_qos_req))
                   return -EINVAL;
   
           o = pm_qos_array[pm_qos_req->pm_qos_class];
           spin_lock_irqsave(&pm_qos_lock, flags);
           value = pm_qos_get_value(o);
           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_list *pm_qos_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;
           }
   
           pm_qos_req = filp->private_data;
           pm_qos_update_request(pm_qos_req, value);
   
           return count;
   }
   
   
   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);

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