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#include <linux/kernel.h>
44
45#include <linux/uaccess.h>
46
47/*
48 * locking rule: all changes to requests or notifiers lists
49 * or pm_qos_object list and pm_qos_objects need to happen with pm_qos_lock
50 * held, taken with _irqsave. One lock to rule them all
51 */
52enum pm_qos_type {
53    PM_QOS_MAX, /* return the largest value */
54    PM_QOS_MIN /* return the smallest value */
55};
56
57/*
58 * Note: The lockless read path depends on the CPU accessing
59 * target_value atomically. Atomic access is only guaranteed on all CPU
60 * types linux supports for 32 bit quantites
61 */
62struct pm_qos_object {
63    struct plist_head requests;
64    struct blocking_notifier_head *notifiers;
65    struct miscdevice pm_qos_power_miscdev;
66    char *name;
67    s32 target_value; /* Do not change to 64 bit */
68    s32 default_value;
69    enum pm_qos_type type;
70};
71
72static DEFINE_SPINLOCK(pm_qos_lock);
73
74static struct pm_qos_object null_pm_qos;
75static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
76static struct pm_qos_object cpu_dma_pm_qos = {
77    .requests = PLIST_HEAD_INIT(cpu_dma_pm_qos.requests, pm_qos_lock),
78    .notifiers = &cpu_dma_lat_notifier,
79    .name = "cpu_dma_latency",
80    .target_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE,
81    .default_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE,
82    .type = PM_QOS_MIN,
83};
84
85static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
86static struct pm_qos_object network_lat_pm_qos = {
87    .requests = PLIST_HEAD_INIT(network_lat_pm_qos.requests, pm_qos_lock),
88    .notifiers = &network_lat_notifier,
89    .name = "network_latency",
90    .target_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
91    .default_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
92    .type = PM_QOS_MIN
93};
94
95
96static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
97static struct pm_qos_object network_throughput_pm_qos = {
98    .requests = PLIST_HEAD_INIT(network_throughput_pm_qos.requests, pm_qos_lock),
99    .notifiers = &network_throughput_notifier,
100    .name = "network_throughput",
101    .target_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
102    .default_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
103    .type = PM_QOS_MAX,
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 ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
115        size_t count, loff_t *f_pos);
116static ssize_t pm_qos_power_read(struct file *filp, 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    .read = pm_qos_power_read,
124    .open = pm_qos_power_open,
125    .release = pm_qos_power_release,
126    .llseek = noop_llseek,
127};
128
129/* unlocked internal variant */
130static inline int pm_qos_get_value(struct pm_qos_object *o)
131{
132    if (plist_head_empty(&o->requests))
133        return o->default_value;
134
135    switch (o->type) {
136    case PM_QOS_MIN:
137        return plist_first(&o->requests)->prio;
138
139    case PM_QOS_MAX:
140        return plist_last(&o->requests)->prio;
141
142    default:
143        /* runtime check for not using enum */
144        BUG();
145    }
146}
147
148static inline s32 pm_qos_read_value(struct pm_qos_object *o)
149{
150    return o->target_value;
151}
152
153static inline void pm_qos_set_value(struct pm_qos_object *o, s32 value)
154{
155    o->target_value = value;
156}
157
158static void update_target(struct pm_qos_object *o, struct plist_node *node,
159              int del, int value)
160{
161    unsigned long flags;
162    int prev_value, curr_value;
163
164    spin_lock_irqsave(&pm_qos_lock, flags);
165    prev_value = pm_qos_get_value(o);
166    /* PM_QOS_DEFAULT_VALUE is a signal that the value is unchanged */
167    if (value != PM_QOS_DEFAULT_VALUE) {
168        /*
169         * to change the list, we atomically remove, reinit
170         * with new value and add, then see if the extremal
171         * changed
172         */
173        plist_del(node, &o->requests);
174        plist_node_init(node, value);
175        plist_add(node, &o->requests);
176    } else if (del) {
177        plist_del(node, &o->requests);
178    } else {
179        plist_add(node, &o->requests);
180    }
181    curr_value = pm_qos_get_value(o);
182    pm_qos_set_value(o, curr_value);
183    spin_unlock_irqrestore(&pm_qos_lock, flags);
184
185    if (prev_value != curr_value)
186        blocking_notifier_call_chain(o->notifiers,
187                         (unsigned long)curr_value,
188                         NULL);
189}
190
191static int register_pm_qos_misc(struct pm_qos_object *qos)
192{
193    qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
194    qos->pm_qos_power_miscdev.name = qos->name;
195    qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;
196
197    return misc_register(&qos->pm_qos_power_miscdev);
198}
199
200static int find_pm_qos_object_by_minor(int minor)
201{
202    int pm_qos_class;
203
204    for (pm_qos_class = 0;
205        pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
206        if (minor ==
207            pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
208            return pm_qos_class;
209    }
210    return -1;
211}
212
213/**
214 * pm_qos_request - returns current system wide qos expectation
215 * @pm_qos_class: identification of which qos value is requested
216 *
217 * This function returns the current target value.
218 */
219int pm_qos_request(int pm_qos_class)
220{
221    return pm_qos_read_value(pm_qos_array[pm_qos_class]);
222}
223EXPORT_SYMBOL_GPL(pm_qos_request);
224
225int pm_qos_request_active(struct pm_qos_request_list *req)
226{
227    return req->pm_qos_class != 0;
228}
229EXPORT_SYMBOL_GPL(pm_qos_request_active);
230
231/**
232 * pm_qos_add_request - inserts new qos request into the list
233 * @dep: pointer to a preallocated handle
234 * @pm_qos_class: identifies which list of qos request to use
235 * @value: defines the qos request
236 *
237 * This function inserts a new entry in the pm_qos_class list of requested qos
238 * performance characteristics. It recomputes the aggregate QoS expectations
239 * for the pm_qos_class of parameters and initializes the pm_qos_request_list
240 * handle. Caller needs to save this handle for later use in updates and
241 * removal.
242 */
243
244void pm_qos_add_request(struct pm_qos_request_list *dep,
245            int pm_qos_class, s32 value)
246{
247    struct pm_qos_object *o = pm_qos_array[pm_qos_class];
248    int new_value;
249
250    if (pm_qos_request_active(dep)) {
251        WARN(1, KERN_ERR "pm_qos_add_request() called for already added request\n");
252        return;
253    }
254    if (value == PM_QOS_DEFAULT_VALUE)
255        new_value = o->default_value;
256    else
257        new_value = value;
258    plist_node_init(&dep->list, new_value);
259    dep->pm_qos_class = pm_qos_class;
260    update_target(o, &dep->list, 0, PM_QOS_DEFAULT_VALUE);
261}
262EXPORT_SYMBOL_GPL(pm_qos_add_request);
263
264/**
265 * pm_qos_update_request - modifies an existing qos request
266 * @pm_qos_req : handle to list element holding a pm_qos request to use
267 * @value: defines the qos request
268 *
269 * Updates an existing qos request for the pm_qos_class of parameters along
270 * with updating the target pm_qos_class value.
271 *
272 * Attempts are made to make this code callable on hot code paths.
273 */
274void pm_qos_update_request(struct pm_qos_request_list *pm_qos_req,
275               s32 new_value)
276{
277    s32 temp;
278    struct pm_qos_object *o;
279
280    if (!pm_qos_req) /*guard against callers passing in null */
281        return;
282
283    if (!pm_qos_request_active(pm_qos_req)) {
284        WARN(1, KERN_ERR "pm_qos_update_request() called for unknown object\n");
285        return;
286    }
287
288    o = pm_qos_array[pm_qos_req->pm_qos_class];
289
290    if (new_value == PM_QOS_DEFAULT_VALUE)
291        temp = o->default_value;
292    else
293        temp = new_value;
294
295    if (temp != pm_qos_req->list.prio)
296        update_target(o, &pm_qos_req->list, 0, temp);
297}
298EXPORT_SYMBOL_GPL(pm_qos_update_request);
299
300/**
301 * pm_qos_remove_request - modifies an existing qos request
302 * @pm_qos_req: handle to request list element
303 *
304 * Will remove pm qos request from the list of requests and
305 * recompute the current target value for the pm_qos_class. Call this
306 * on slow code paths.
307 */
308void pm_qos_remove_request(struct pm_qos_request_list *pm_qos_req)
309{
310    struct pm_qos_object *o;
311
312    if (pm_qos_req == NULL)
313        return;
314        /* silent return to keep pcm code cleaner */
315
316    if (!pm_qos_request_active(pm_qos_req)) {
317        WARN(1, KERN_ERR "pm_qos_remove_request() called for unknown object\n");
318        return;
319    }
320
321    o = pm_qos_array[pm_qos_req->pm_qos_class];
322    update_target(o, &pm_qos_req->list, 1, PM_QOS_DEFAULT_VALUE);
323    memset(pm_qos_req, 0, sizeof(*pm_qos_req));
324}
325EXPORT_SYMBOL_GPL(pm_qos_remove_request);
326
327/**
328 * pm_qos_add_notifier - sets notification entry for changes to target value
329 * @pm_qos_class: identifies which qos target changes should be notified.
330 * @notifier: notifier block managed by caller.
331 *
332 * will register the notifier into a notification chain that gets called
333 * upon changes to the pm_qos_class target value.
334 */
335int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
336{
337    int retval;
338
339    retval = blocking_notifier_chain_register(
340            pm_qos_array[pm_qos_class]->notifiers, notifier);
341
342    return retval;
343}
344EXPORT_SYMBOL_GPL(pm_qos_add_notifier);
345
346/**
347 * pm_qos_remove_notifier - deletes notification entry from chain.
348 * @pm_qos_class: identifies which qos target changes are notified.
349 * @notifier: notifier block to be removed.
350 *
351 * will remove the notifier from the notification chain that gets called
352 * upon changes to the pm_qos_class target value.
353 */
354int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
355{
356    int retval;
357
358    retval = blocking_notifier_chain_unregister(
359            pm_qos_array[pm_qos_class]->notifiers, notifier);
360
361    return retval;
362}
363EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);
364
365static int pm_qos_power_open(struct inode *inode, struct file *filp)
366{
367    long pm_qos_class;
368
369    pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
370    if (pm_qos_class >= 0) {
371               struct pm_qos_request_list *req = kzalloc(sizeof(*req), GFP_KERNEL);
372        if (!req)
373            return -ENOMEM;
374
375        pm_qos_add_request(req, pm_qos_class, PM_QOS_DEFAULT_VALUE);
376        filp->private_data = req;
377
378        if (filp->private_data)
379            return 0;
380    }
381    return -EPERM;
382}
383
384static int pm_qos_power_release(struct inode *inode, struct file *filp)
385{
386    struct pm_qos_request_list *req;
387
388    req = filp->private_data;
389    pm_qos_remove_request(req);
390    kfree(req);
391
392    return 0;
393}
394
395
396static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
397        size_t count, loff_t *f_pos)
398{
399    s32 value;
400    unsigned long flags;
401    struct pm_qos_object *o;
402    struct pm_qos_request_list *pm_qos_req = filp->private_data;
403
404    if (!pm_qos_req)
405        return -EINVAL;
406    if (!pm_qos_request_active(pm_qos_req))
407        return -EINVAL;
408
409    o = pm_qos_array[pm_qos_req->pm_qos_class];
410    spin_lock_irqsave(&pm_qos_lock, flags);
411    value = pm_qos_get_value(o);
412    spin_unlock_irqrestore(&pm_qos_lock, flags);
413
414    return simple_read_from_buffer(buf, count, f_pos, &value, sizeof(s32));
415}
416
417static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
418        size_t count, loff_t *f_pos)
419{
420    s32 value;
421    struct pm_qos_request_list *pm_qos_req;
422
423    if (count == sizeof(s32)) {
424        if (copy_from_user(&value, buf, sizeof(s32)))
425            return -EFAULT;
426    } else if (count <= 11) { /* ASCII perhaps? */
427        char ascii_value[11];
428        unsigned long int ulval;
429        int ret;
430
431        if (copy_from_user(ascii_value, buf, count))
432            return -EFAULT;
433
434        if (count > 10) {
435            if (ascii_value[10] == '\n')
436                ascii_value[10] = '\0';
437            else
438                return -EINVAL;
439        } else {
440            ascii_value[count] = '\0';
441        }
442        ret = strict_strtoul(ascii_value, 16, &ulval);
443        if (ret) {
444            pr_debug("%s, 0x%lx, 0x%x\n", ascii_value, ulval, ret);
445            return -EINVAL;
446        }
447        value = (s32)lower_32_bits(ulval);
448    } else {
449        return -EINVAL;
450    }
451
452    pm_qos_req = filp->private_data;
453    pm_qos_update_request(pm_qos_req, value);
454
455    return count;
456}
457
458
459static int __init pm_qos_power_init(void)
460{
461    int ret = 0;
462
463    ret = register_pm_qos_misc(&cpu_dma_pm_qos);
464    if (ret < 0) {
465        printk(KERN_ERR "pm_qos_param: cpu_dma_latency setup failed\n");
466        return ret;
467    }
468    ret = register_pm_qos_misc(&network_lat_pm_qos);
469    if (ret < 0) {
470        printk(KERN_ERR "pm_qos_param: network_latency setup failed\n");
471        return ret;
472    }
473    ret = register_pm_qos_misc(&network_throughput_pm_qos);
474    if (ret < 0)
475        printk(KERN_ERR
476            "pm_qos_param: network_throughput setup failed\n");
477
478    return ret;
479}
480
481late_initcall(pm_qos_power_init);
482

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