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 requests
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 requests, notifiers
18 *
19 * User mode requests 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 * request is removed and a new qos target is computed. This way when the
24 * request 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/*#define DEBUG*/
31
32#include <linux/pm_qos_params.h>
33#include <linux/sched.h>
34#include <linux/spinlock.h>
35#include <linux/slab.h>
36#include <linux/time.h>
37#include <linux/fs.h>
38#include <linux/device.h>
39#include <linux/miscdevice.h>
40#include <linux/string.h>
41#include <linux/platform_device.h>
42#include <linux/init.h>
43
44#include <linux/uaccess.h>
45
46/*
47 * locking rule: all changes to requests or notifiers lists
48 * or pm_qos_object list and pm_qos_objects need to happen with pm_qos_lock
49 * held, taken with _irqsave. One lock to rule them all
50 */
51enum pm_qos_type {
52    PM_QOS_MAX, /* return the largest value */
53    PM_QOS_MIN /* return the smallest value */
54};
55
56struct pm_qos_object {
57    struct plist_head requests;
58    struct blocking_notifier_head *notifiers;
59    struct miscdevice pm_qos_power_miscdev;
60    char *name;
61    s32 default_value;
62    enum pm_qos_type type;
63};
64
65static DEFINE_SPINLOCK(pm_qos_lock);
66
67static struct pm_qos_object null_pm_qos;
68static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
69static struct pm_qos_object cpu_dma_pm_qos = {
70    .requests = PLIST_HEAD_INIT(cpu_dma_pm_qos.requests, pm_qos_lock),
71    .notifiers = &cpu_dma_lat_notifier,
72    .name = "cpu_dma_latency",
73    .default_value = 2000 * USEC_PER_SEC,
74    .type = PM_QOS_MIN,
75};
76
77static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
78static struct pm_qos_object network_lat_pm_qos = {
79    .requests = PLIST_HEAD_INIT(network_lat_pm_qos.requests, pm_qos_lock),
80    .notifiers = &network_lat_notifier,
81    .name = "network_latency",
82    .default_value = 2000 * USEC_PER_SEC,
83    .type = PM_QOS_MIN
84};
85
86
87static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
88static struct pm_qos_object network_throughput_pm_qos = {
89    .requests = PLIST_HEAD_INIT(network_throughput_pm_qos.requests, pm_qos_lock),
90    .notifiers = &network_throughput_notifier,
91    .name = "network_throughput",
92    .default_value = 0,
93    .type = PM_QOS_MAX,
94};
95
96
97static struct pm_qos_object *pm_qos_array[] = {
98    &null_pm_qos,
99    &cpu_dma_pm_qos,
100    &network_lat_pm_qos,
101    &network_throughput_pm_qos
102};
103
104static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
105        size_t count, loff_t *f_pos);
106static int pm_qos_power_open(struct inode *inode, struct file *filp);
107static int pm_qos_power_release(struct inode *inode, struct file *filp);
108
109static const struct file_operations pm_qos_power_fops = {
110    .write = pm_qos_power_write,
111    .open = pm_qos_power_open,
112    .release = pm_qos_power_release,
113    .llseek = noop_llseek,
114};
115
116/* unlocked internal variant */
117static inline int pm_qos_get_value(struct pm_qos_object *o)
118{
119    if (plist_head_empty(&o->requests))
120        return o->default_value;
121
122    switch (o->type) {
123    case PM_QOS_MIN:
124        return plist_first(&o->requests)->prio;
125
126    case PM_QOS_MAX:
127        return plist_last(&o->requests)->prio;
128
129    default:
130        /* runtime check for not using enum */
131        BUG();
132    }
133}
134
135static void update_target(struct pm_qos_object *o, struct plist_node *node,
136              int del, int value)
137{
138    unsigned long flags;
139    int prev_value, curr_value;
140
141    spin_lock_irqsave(&pm_qos_lock, flags);
142    prev_value = pm_qos_get_value(o);
143    /* PM_QOS_DEFAULT_VALUE is a signal that the value is unchanged */
144    if (value != PM_QOS_DEFAULT_VALUE) {
145        /*
146         * to change the list, we atomically remove, reinit
147         * with new value and add, then see if the extremal
148         * changed
149         */
150        plist_del(node, &o->requests);
151        plist_node_init(node, value);
152        plist_add(node, &o->requests);
153    } else if (del) {
154        plist_del(node, &o->requests);
155    } else {
156        plist_add(node, &o->requests);
157    }
158    curr_value = pm_qos_get_value(o);
159    spin_unlock_irqrestore(&pm_qos_lock, flags);
160
161    if (prev_value != curr_value)
162        blocking_notifier_call_chain(o->notifiers,
163                         (unsigned long)curr_value,
164                         NULL);
165}
166
167static int register_pm_qos_misc(struct pm_qos_object *qos)
168{
169    qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
170    qos->pm_qos_power_miscdev.name = qos->name;
171    qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;
172
173    return misc_register(&qos->pm_qos_power_miscdev);
174}
175
176static int find_pm_qos_object_by_minor(int minor)
177{
178    int pm_qos_class;
179
180    for (pm_qos_class = 0;
181        pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
182        if (minor ==
183            pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
184            return pm_qos_class;
185    }
186    return -1;
187}
188
189/**
190 * pm_qos_request - returns current system wide qos expectation
191 * @pm_qos_class: identification of which qos value is requested
192 *
193 * This function returns the current target value in an atomic manner.
194 */
195int pm_qos_request(int pm_qos_class)
196{
197    unsigned long flags;
198    int value;
199
200    spin_lock_irqsave(&pm_qos_lock, flags);
201    value = pm_qos_get_value(pm_qos_array[pm_qos_class]);
202    spin_unlock_irqrestore(&pm_qos_lock, flags);
203
204    return value;
205}
206EXPORT_SYMBOL_GPL(pm_qos_request);
207
208int pm_qos_request_active(struct pm_qos_request_list *req)
209{
210    return req->pm_qos_class != 0;
211}
212EXPORT_SYMBOL_GPL(pm_qos_request_active);
213
214/**
215 * pm_qos_add_request - inserts new qos request into the list
216 * @dep: pointer to a preallocated handle
217 * @pm_qos_class: identifies which list of qos request to use
218 * @value: defines the qos request
219 *
220 * This function inserts a new entry in the pm_qos_class list of requested qos
221 * performance characteristics. It recomputes the aggregate QoS expectations
222 * for the pm_qos_class of parameters and initializes the pm_qos_request_list
223 * handle. Caller needs to save this handle for later use in updates and
224 * removal.
225 */
226
227void pm_qos_add_request(struct pm_qos_request_list *dep,
228            int pm_qos_class, s32 value)
229{
230    struct pm_qos_object *o = pm_qos_array[pm_qos_class];
231    int new_value;
232
233    if (pm_qos_request_active(dep)) {
234        WARN(1, KERN_ERR "pm_qos_add_request() called for already added request\n");
235        return;
236    }
237    if (value == PM_QOS_DEFAULT_VALUE)
238        new_value = o->default_value;
239    else
240        new_value = value;
241    plist_node_init(&dep->list, new_value);
242    dep->pm_qos_class = pm_qos_class;
243    update_target(o, &dep->list, 0, PM_QOS_DEFAULT_VALUE);
244}
245EXPORT_SYMBOL_GPL(pm_qos_add_request);
246
247/**
248 * pm_qos_update_request - modifies an existing qos request
249 * @pm_qos_req : handle to list element holding a pm_qos request to use
250 * @value: defines the qos request
251 *
252 * Updates an existing qos request for the pm_qos_class of parameters along
253 * with updating the target pm_qos_class value.
254 *
255 * Attempts are made to make this code callable on hot code paths.
256 */
257void pm_qos_update_request(struct pm_qos_request_list *pm_qos_req,
258               s32 new_value)
259{
260    s32 temp;
261    struct pm_qos_object *o;
262
263    if (!pm_qos_req) /*guard against callers passing in null */
264        return;
265
266    if (!pm_qos_request_active(pm_qos_req)) {
267        WARN(1, KERN_ERR "pm_qos_update_request() called for unknown object\n");
268        return;
269    }
270
271    o = pm_qos_array[pm_qos_req->pm_qos_class];
272
273    if (new_value == PM_QOS_DEFAULT_VALUE)
274        temp = o->default_value;
275    else
276        temp = new_value;
277
278    if (temp != pm_qos_req->list.prio)
279        update_target(o, &pm_qos_req->list, 0, temp);
280}
281EXPORT_SYMBOL_GPL(pm_qos_update_request);
282
283/**
284 * pm_qos_remove_request - modifies an existing qos request
285 * @pm_qos_req: handle to request list element
286 *
287 * Will remove pm qos request from the list of requests and
288 * recompute the current target value for the pm_qos_class. Call this
289 * on slow code paths.
290 */
291void pm_qos_remove_request(struct pm_qos_request_list *pm_qos_req)
292{
293    struct pm_qos_object *o;
294
295    if (pm_qos_req == NULL)
296        return;
297        /* silent return to keep pcm code cleaner */
298
299    if (!pm_qos_request_active(pm_qos_req)) {
300        WARN(1, KERN_ERR "pm_qos_remove_request() called for unknown object\n");
301        return;
302    }
303
304    o = pm_qos_array[pm_qos_req->pm_qos_class];
305    update_target(o, &pm_qos_req->list, 1, PM_QOS_DEFAULT_VALUE);
306    memset(pm_qos_req, 0, sizeof(*pm_qos_req));
307}
308EXPORT_SYMBOL_GPL(pm_qos_remove_request);
309
310/**
311 * pm_qos_add_notifier - sets notification entry for changes to target value
312 * @pm_qos_class: identifies which qos target changes should be notified.
313 * @notifier: notifier block managed by caller.
314 *
315 * will register the notifier into a notification chain that gets called
316 * upon changes to the pm_qos_class target value.
317 */
318int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
319{
320    int retval;
321
322    retval = blocking_notifier_chain_register(
323            pm_qos_array[pm_qos_class]->notifiers, notifier);
324
325    return retval;
326}
327EXPORT_SYMBOL_GPL(pm_qos_add_notifier);
328
329/**
330 * pm_qos_remove_notifier - deletes notification entry from chain.
331 * @pm_qos_class: identifies which qos target changes are notified.
332 * @notifier: notifier block to be removed.
333 *
334 * will remove the notifier from the notification chain that gets called
335 * upon changes to the pm_qos_class target value.
336 */
337int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
338{
339    int retval;
340
341    retval = blocking_notifier_chain_unregister(
342            pm_qos_array[pm_qos_class]->notifiers, notifier);
343
344    return retval;
345}
346EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);
347
348static int pm_qos_power_open(struct inode *inode, struct file *filp)
349{
350    long pm_qos_class;
351
352    pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
353    if (pm_qos_class >= 0) {
354               struct pm_qos_request_list *req = kzalloc(sizeof(*req), GFP_KERNEL);
355        if (!req)
356            return -ENOMEM;
357
358        pm_qos_add_request(req, pm_qos_class, PM_QOS_DEFAULT_VALUE);
359        filp->private_data = req;
360
361        if (filp->private_data)
362            return 0;
363    }
364    return -EPERM;
365}
366
367static int pm_qos_power_release(struct inode *inode, struct file *filp)
368{
369    struct pm_qos_request_list *req;
370
371    req = filp->private_data;
372    pm_qos_remove_request(req);
373    kfree(req);
374
375    return 0;
376}
377
378
379static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
380        size_t count, loff_t *f_pos)
381{
382    s32 value;
383    int x;
384    char ascii_value[11];
385    struct pm_qos_request_list *pm_qos_req;
386
387    if (count == sizeof(s32)) {
388        if (copy_from_user(&value, buf, sizeof(s32)))
389            return -EFAULT;
390    } else if (count == 11) { /* len('0x12345678/0') */
391        if (copy_from_user(ascii_value, buf, 11))
392            return -EFAULT;
393        if (strlen(ascii_value) != 10)
394            return -EINVAL;
395        x = sscanf(ascii_value, "%x", &value);
396        if (x != 1)
397            return -EINVAL;
398        pr_debug("%s, %d, 0x%x\n", ascii_value, x, value);
399    } else
400        return -EINVAL;
401
402    pm_qos_req = filp->private_data;
403    pm_qos_update_request(pm_qos_req, value);
404
405    return count;
406}
407
408
409static int __init pm_qos_power_init(void)
410{
411    int ret = 0;
412
413    ret = register_pm_qos_misc(&cpu_dma_pm_qos);
414    if (ret < 0) {
415        printk(KERN_ERR "pm_qos_param: cpu_dma_latency setup failed\n");
416        return ret;
417    }
418    ret = register_pm_qos_misc(&network_lat_pm_qos);
419    if (ret < 0) {
420        printk(KERN_ERR "pm_qos_param: network_latency setup failed\n");
421        return ret;
422    }
423    ret = register_pm_qos_misc(&network_throughput_pm_qos);
424    if (ret < 0)
425        printk(KERN_ERR
426            "pm_qos_param: network_throughput setup failed\n");
427
428    return ret;
429}
430
431late_initcall(pm_qos_power_init);
432

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