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

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