Root/kernel/pm_qos_params.c

1/*
2 * This module exposes the interface to kernel space for specifying
3 * QoS dependencies. It provides infrastructure for registration of:
4 *
5 * Dependents on a QoS value : register requirements
6 * Watchers of QoS value : get notified when target QoS value changes
7 *
8 * This QoS design is best effort based. Dependents register their QoS needs.
9 * Watchers register to keep track of the current QoS needs of the system.
10 *
11 * There are 3 basic classes of QoS parameter: latency, timeout, throughput
12 * each have defined units:
13 * latency: usec
14 * timeout: usec <-- currently not used.
15 * throughput: kbs (kilo byte / sec)
16 *
17 * There are lists of pm_qos_objects each one wrapping requirements, notifiers
18 *
19 * User mode requirements on a QOS parameter register themselves to the
20 * subsystem by opening the device node /dev/... and writing there request to
21 * the node. As long as the process holds a file handle open to the node the
22 * client continues to be accounted for. Upon file release the usermode
23 * requirement is removed and a new qos target is computed. This way when the
24 * requirement that the application has is cleaned up when closes the file
25 * pointer or exits the pm_qos_object will get an opportunity to clean up.
26 *
27 * Mark Gross <mgross@linux.intel.com>
28 */
29
30#include <linux/pm_qos_params.h>
31#include <linux/sched.h>
32#include <linux/smp_lock.h>
33#include <linux/spinlock.h>
34#include <linux/slab.h>
35#include <linux/time.h>
36#include <linux/fs.h>
37#include <linux/device.h>
38#include <linux/miscdevice.h>
39#include <linux/string.h>
40#include <linux/platform_device.h>
41#include <linux/init.h>
42
43#include <linux/uaccess.h>
44
45/*
46 * locking rule: all changes to requirements or notifiers lists
47 * or pm_qos_object list and pm_qos_objects need to happen with pm_qos_lock
48 * held, taken with _irqsave. One lock to rule them all
49 */
50struct requirement_list {
51    struct list_head list;
52    union {
53        s32 value;
54        s32 usec;
55        s32 kbps;
56    };
57    char *name;
58};
59
60static s32 max_compare(s32 v1, s32 v2);
61static s32 min_compare(s32 v1, s32 v2);
62
63struct pm_qos_object {
64    struct requirement_list requirements;
65    struct blocking_notifier_head *notifiers;
66    struct miscdevice pm_qos_power_miscdev;
67    char *name;
68    s32 default_value;
69    atomic_t target_value;
70    s32 (*comparitor)(s32, s32);
71};
72
73static struct pm_qos_object null_pm_qos;
74static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
75static struct pm_qos_object cpu_dma_pm_qos = {
76    .requirements = {LIST_HEAD_INIT(cpu_dma_pm_qos.requirements.list)},
77    .notifiers = &cpu_dma_lat_notifier,
78    .name = "cpu_dma_latency",
79    .default_value = 2000 * USEC_PER_SEC,
80    .target_value = ATOMIC_INIT(2000 * USEC_PER_SEC),
81    .comparitor = min_compare
82};
83
84static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
85static struct pm_qos_object network_lat_pm_qos = {
86    .requirements = {LIST_HEAD_INIT(network_lat_pm_qos.requirements.list)},
87    .notifiers = &network_lat_notifier,
88    .name = "network_latency",
89    .default_value = 2000 * USEC_PER_SEC,
90    .target_value = ATOMIC_INIT(2000 * USEC_PER_SEC),
91    .comparitor = min_compare
92};
93
94
95static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
96static struct pm_qos_object network_throughput_pm_qos = {
97    .requirements =
98        {LIST_HEAD_INIT(network_throughput_pm_qos.requirements.list)},
99    .notifiers = &network_throughput_notifier,
100    .name = "network_throughput",
101    .default_value = 0,
102    .target_value = ATOMIC_INIT(0),
103    .comparitor = max_compare
104};
105
106
107static struct pm_qos_object *pm_qos_array[] = {
108    &null_pm_qos,
109    &cpu_dma_pm_qos,
110    &network_lat_pm_qos,
111    &network_throughput_pm_qos
112};
113
114static DEFINE_SPINLOCK(pm_qos_lock);
115
116static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
117        size_t count, loff_t *f_pos);
118static int pm_qos_power_open(struct inode *inode, struct file *filp);
119static int pm_qos_power_release(struct inode *inode, struct file *filp);
120
121static const struct file_operations pm_qos_power_fops = {
122    .write = pm_qos_power_write,
123    .open = pm_qos_power_open,
124    .release = pm_qos_power_release,
125};
126
127/* static helper functions */
128static s32 max_compare(s32 v1, s32 v2)
129{
130    return max(v1, v2);
131}
132
133static s32 min_compare(s32 v1, s32 v2)
134{
135    return min(v1, v2);
136}
137
138
139static void update_target(int target)
140{
141    s32 extreme_value;
142    struct requirement_list *node;
143    unsigned long flags;
144    int call_notifier = 0;
145
146    spin_lock_irqsave(&pm_qos_lock, flags);
147    extreme_value = pm_qos_array[target]->default_value;
148    list_for_each_entry(node,
149            &pm_qos_array[target]->requirements.list, list) {
150        extreme_value = pm_qos_array[target]->comparitor(
151                extreme_value, node->value);
152    }
153    if (atomic_read(&pm_qos_array[target]->target_value) != extreme_value) {
154        call_notifier = 1;
155        atomic_set(&pm_qos_array[target]->target_value, extreme_value);
156        pr_debug(KERN_ERR "new target for qos %d is %d\n", target,
157            atomic_read(&pm_qos_array[target]->target_value));
158    }
159    spin_unlock_irqrestore(&pm_qos_lock, flags);
160
161    if (call_notifier)
162        blocking_notifier_call_chain(pm_qos_array[target]->notifiers,
163            (unsigned long) extreme_value, NULL);
164}
165
166static int register_pm_qos_misc(struct pm_qos_object *qos)
167{
168    qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
169    qos->pm_qos_power_miscdev.name = qos->name;
170    qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;
171
172    return misc_register(&qos->pm_qos_power_miscdev);
173}
174
175static int find_pm_qos_object_by_minor(int minor)
176{
177    int pm_qos_class;
178
179    for (pm_qos_class = 0;
180        pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
181        if (minor ==
182            pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
183            return pm_qos_class;
184    }
185    return -1;
186}
187
188/**
189 * pm_qos_requirement - returns current system wide qos expectation
190 * @pm_qos_class: identification of which qos value is requested
191 *
192 * This function returns the current target value in an atomic manner.
193 */
194int pm_qos_requirement(int pm_qos_class)
195{
196    return atomic_read(&pm_qos_array[pm_qos_class]->target_value);
197}
198EXPORT_SYMBOL_GPL(pm_qos_requirement);
199
200/**
201 * pm_qos_add_requirement - inserts new qos request into the list
202 * @pm_qos_class: identifies which list of qos request to us
203 * @name: identifies the request
204 * @value: defines the qos request
205 *
206 * This function inserts a new entry in the pm_qos_class list of requested qos
207 * performance characteristics. It recomputes the aggregate QoS expectations
208 * for the pm_qos_class of parameters.
209 */
210int pm_qos_add_requirement(int pm_qos_class, char *name, s32 value)
211{
212    struct requirement_list *dep;
213    unsigned long flags;
214
215    dep = kzalloc(sizeof(struct requirement_list), GFP_KERNEL);
216    if (dep) {
217        if (value == PM_QOS_DEFAULT_VALUE)
218            dep->value = pm_qos_array[pm_qos_class]->default_value;
219        else
220            dep->value = value;
221        dep->name = kstrdup(name, GFP_KERNEL);
222        if (!dep->name)
223            goto cleanup;
224
225        spin_lock_irqsave(&pm_qos_lock, flags);
226        list_add(&dep->list,
227            &pm_qos_array[pm_qos_class]->requirements.list);
228        spin_unlock_irqrestore(&pm_qos_lock, flags);
229        update_target(pm_qos_class);
230
231        return 0;
232    }
233
234cleanup:
235    kfree(dep);
236    return -ENOMEM;
237}
238EXPORT_SYMBOL_GPL(pm_qos_add_requirement);
239
240/**
241 * pm_qos_update_requirement - modifies an existing qos request
242 * @pm_qos_class: identifies which list of qos request to us
243 * @name: identifies the request
244 * @value: defines the qos request
245 *
246 * Updates an existing qos requirement for the pm_qos_class of parameters along
247 * with updating the target pm_qos_class value.
248 *
249 * If the named request isn't in the list then no change is made.
250 */
251int pm_qos_update_requirement(int pm_qos_class, char *name, s32 new_value)
252{
253    unsigned long flags;
254    struct requirement_list *node;
255    int pending_update = 0;
256
257    spin_lock_irqsave(&pm_qos_lock, flags);
258    list_for_each_entry(node,
259        &pm_qos_array[pm_qos_class]->requirements.list, list) {
260        if (strcmp(node->name, name) == 0) {
261            if (new_value == PM_QOS_DEFAULT_VALUE)
262                node->value =
263                pm_qos_array[pm_qos_class]->default_value;
264            else
265                node->value = new_value;
266            pending_update = 1;
267            break;
268        }
269    }
270    spin_unlock_irqrestore(&pm_qos_lock, flags);
271    if (pending_update)
272        update_target(pm_qos_class);
273
274    return 0;
275}
276EXPORT_SYMBOL_GPL(pm_qos_update_requirement);
277
278/**
279 * pm_qos_remove_requirement - modifies an existing qos request
280 * @pm_qos_class: identifies which list of qos request to us
281 * @name: identifies the request
282 *
283 * Will remove named qos request from pm_qos_class list of parameters and
284 * recompute the current target value for the pm_qos_class.
285 */
286void pm_qos_remove_requirement(int pm_qos_class, char *name)
287{
288    unsigned long flags;
289    struct requirement_list *node;
290    int pending_update = 0;
291
292    spin_lock_irqsave(&pm_qos_lock, flags);
293    list_for_each_entry(node,
294        &pm_qos_array[pm_qos_class]->requirements.list, list) {
295        if (strcmp(node->name, name) == 0) {
296            kfree(node->name);
297            list_del(&node->list);
298            kfree(node);
299            pending_update = 1;
300            break;
301        }
302    }
303    spin_unlock_irqrestore(&pm_qos_lock, flags);
304    if (pending_update)
305        update_target(pm_qos_class);
306}
307EXPORT_SYMBOL_GPL(pm_qos_remove_requirement);
308
309/**
310 * pm_qos_add_notifier - sets notification entry for changes to target value
311 * @pm_qos_class: identifies which qos target changes should be notified.
312 * @notifier: notifier block managed by caller.
313 *
314 * will register the notifier into a notification chain that gets called
315 * upon changes to the pm_qos_class target value.
316 */
317 int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
318{
319    int retval;
320
321    retval = blocking_notifier_chain_register(
322            pm_qos_array[pm_qos_class]->notifiers, notifier);
323
324    return retval;
325}
326EXPORT_SYMBOL_GPL(pm_qos_add_notifier);
327
328/**
329 * pm_qos_remove_notifier - deletes notification entry from chain.
330 * @pm_qos_class: identifies which qos target changes are notified.
331 * @notifier: notifier block to be removed.
332 *
333 * will remove the notifier from the notification chain that gets called
334 * upon changes to the pm_qos_class target value.
335 */
336int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
337{
338    int retval;
339
340    retval = blocking_notifier_chain_unregister(
341            pm_qos_array[pm_qos_class]->notifiers, notifier);
342
343    return retval;
344}
345EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);
346
347#define PID_NAME_LEN sizeof("process_1234567890")
348static char name[PID_NAME_LEN];
349
350static int pm_qos_power_open(struct inode *inode, struct file *filp)
351{
352    int ret;
353    long pm_qos_class;
354
355    lock_kernel();
356    pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
357    if (pm_qos_class >= 0) {
358        filp->private_data = (void *)pm_qos_class;
359        sprintf(name, "process_%d", current->pid);
360        ret = pm_qos_add_requirement(pm_qos_class, name,
361                    PM_QOS_DEFAULT_VALUE);
362        if (ret >= 0) {
363            unlock_kernel();
364            return 0;
365        }
366    }
367    unlock_kernel();
368
369    return -EPERM;
370}
371
372static int pm_qos_power_release(struct inode *inode, struct file *filp)
373{
374    int pm_qos_class;
375
376    pm_qos_class = (long)filp->private_data;
377    sprintf(name, "process_%d", current->pid);
378    pm_qos_remove_requirement(pm_qos_class, name);
379
380    return 0;
381}
382
383static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
384        size_t count, loff_t *f_pos)
385{
386    s32 value;
387    int pm_qos_class;
388
389    pm_qos_class = (long)filp->private_data;
390    if (count != sizeof(s32))
391        return -EINVAL;
392    if (copy_from_user(&value, buf, sizeof(s32)))
393        return -EFAULT;
394    sprintf(name, "process_%d", current->pid);
395    pm_qos_update_requirement(pm_qos_class, name, value);
396
397    return sizeof(s32);
398}
399
400
401static int __init pm_qos_power_init(void)
402{
403    int ret = 0;
404
405    ret = register_pm_qos_misc(&cpu_dma_pm_qos);
406    if (ret < 0) {
407        printk(KERN_ERR "pm_qos_param: cpu_dma_latency setup failed\n");
408        return ret;
409    }
410    ret = register_pm_qos_misc(&network_lat_pm_qos);
411    if (ret < 0) {
412        printk(KERN_ERR "pm_qos_param: network_latency setup failed\n");
413        return ret;
414    }
415    ret = register_pm_qos_misc(&network_throughput_pm_qos);
416    if (ret < 0)
417        printk(KERN_ERR
418            "pm_qos_param: network_throughput setup failed\n");
419
420    return ret;
421}
422
423late_initcall(pm_qos_power_init);
424

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