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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Hardware spinlock framework
4 *
5 * Copyright (C) 2010 Texas Instruments Incorporated - http://www.ti.com
6 *
7 * Contact: Ohad Ben-Cohen <ohad@wizery.com>
8 */
9
10#define pr_fmt(fmt) "%s: " fmt, __func__
11
12#include <linux/delay.h>
13#include <linux/kernel.h>
14#include <linux/module.h>
15#include <linux/spinlock.h>
16#include <linux/types.h>
17#include <linux/err.h>
18#include <linux/jiffies.h>
19#include <linux/radix-tree.h>
20#include <linux/hwspinlock.h>
21#include <linux/pm_runtime.h>
22#include <linux/mutex.h>
23#include <linux/of.h>
24
25#include "hwspinlock_internal.h"
26
27/* retry delay used in atomic context */
28#define HWSPINLOCK_RETRY_DELAY_US 100
29
30/* radix tree tags */
31#define HWSPINLOCK_UNUSED (0) /* tags an hwspinlock as unused */
32
33/*
34 * A radix tree is used to maintain the available hwspinlock instances.
35 * The tree associates hwspinlock pointers with their integer key id,
36 * and provides easy-to-use API which makes the hwspinlock core code simple
37 * and easy to read.
38 *
39 * Radix trees are quick on lookups, and reasonably efficient in terms of
40 * storage, especially with high density usages such as this framework
41 * requires (a continuous range of integer keys, beginning with zero, is
42 * used as the ID's of the hwspinlock instances).
43 *
44 * The radix tree API supports tagging items in the tree, which this
45 * framework uses to mark unused hwspinlock instances (see the
46 * HWSPINLOCK_UNUSED tag above). As a result, the process of querying the
47 * tree, looking for an unused hwspinlock instance, is now reduced to a
48 * single radix tree API call.
49 */
50static RADIX_TREE(hwspinlock_tree, GFP_KERNEL);
51
52/*
53 * Synchronization of access to the tree is achieved using this mutex,
54 * as the radix-tree API requires that users provide all synchronisation.
55 * A mutex is needed because we're using non-atomic radix tree allocations.
56 */
57static DEFINE_MUTEX(hwspinlock_tree_lock);
58
59
60/**
61 * __hwspin_trylock() - attempt to lock a specific hwspinlock
62 * @hwlock: an hwspinlock which we want to trylock
63 * @mode: controls whether local interrupts are disabled or not
64 * @flags: a pointer where the caller's interrupt state will be saved at (if
65 * requested)
66 *
67 * This function attempts to lock an hwspinlock, and will immediately
68 * fail if the hwspinlock is already taken.
69 *
70 * Caution: If the mode is HWLOCK_RAW, that means user must protect the routine
71 * of getting hardware lock with mutex or spinlock. Since in some scenarios,
72 * user need some time-consuming or sleepable operations under the hardware
73 * lock, they need one sleepable lock (like mutex) to protect the operations.
74 *
75 * If the mode is neither HWLOCK_IN_ATOMIC nor HWLOCK_RAW, upon a successful
76 * return from this function, preemption (and possibly interrupts) is disabled,
77 * so the caller must not sleep, and is advised to release the hwspinlock as
78 * soon as possible. This is required in order to minimize remote cores polling
79 * on the hardware interconnect.
80 *
81 * The user decides whether local interrupts are disabled or not, and if yes,
82 * whether he wants their previous state to be saved. It is up to the user
83 * to choose the appropriate @mode of operation, exactly the same way users
84 * should decide between spin_trylock, spin_trylock_irq and
85 * spin_trylock_irqsave.
86 *
87 * Returns 0 if we successfully locked the hwspinlock or -EBUSY if
88 * the hwspinlock was already taken.
89 * This function will never sleep.
90 */
91int __hwspin_trylock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
92{
93 int ret;
94
95 if (WARN_ON(!hwlock || (!flags && mode == HWLOCK_IRQSTATE)))
96 return -EINVAL;
97
98 /*
99 * This spin_lock{_irq, _irqsave} serves three purposes:
100 *
101 * 1. Disable preemption, in order to minimize the period of time
102 * in which the hwspinlock is taken. This is important in order
103 * to minimize the possible polling on the hardware interconnect
104 * by a remote user of this lock.
105 * 2. Make the hwspinlock SMP-safe (so we can take it from
106 * additional contexts on the local host).
107 * 3. Ensure that in_atomic/might_sleep checks catch potential
108 * problems with hwspinlock usage (e.g. scheduler checks like
109 * 'scheduling while atomic' etc.)
110 */
111 switch (mode) {
112 case HWLOCK_IRQSTATE:
113 ret = spin_trylock_irqsave(&hwlock->lock, *flags);
114 break;
115 case HWLOCK_IRQ:
116 ret = spin_trylock_irq(&hwlock->lock);
117 break;
118 case HWLOCK_RAW:
119 case HWLOCK_IN_ATOMIC:
120 ret = 1;
121 break;
122 default:
123 ret = spin_trylock(&hwlock->lock);
124 break;
125 }
126
127 /* is lock already taken by another context on the local cpu ? */
128 if (!ret)
129 return -EBUSY;
130
131 /* try to take the hwspinlock device */
132 ret = hwlock->bank->ops->trylock(hwlock);
133
134 /* if hwlock is already taken, undo spin_trylock_* and exit */
135 if (!ret) {
136 switch (mode) {
137 case HWLOCK_IRQSTATE:
138 spin_unlock_irqrestore(&hwlock->lock, *flags);
139 break;
140 case HWLOCK_IRQ:
141 spin_unlock_irq(&hwlock->lock);
142 break;
143 case HWLOCK_RAW:
144 case HWLOCK_IN_ATOMIC:
145 /* Nothing to do */
146 break;
147 default:
148 spin_unlock(&hwlock->lock);
149 break;
150 }
151
152 return -EBUSY;
153 }
154
155 /*
156 * We can be sure the other core's memory operations
157 * are observable to us only _after_ we successfully take
158 * the hwspinlock, and we must make sure that subsequent memory
159 * operations (both reads and writes) will not be reordered before
160 * we actually took the hwspinlock.
161 *
162 * Note: the implicit memory barrier of the spinlock above is too
163 * early, so we need this additional explicit memory barrier.
164 */
165 mb();
166
167 return 0;
168}
169EXPORT_SYMBOL_GPL(__hwspin_trylock);
170
171/**
172 * __hwspin_lock_timeout() - lock an hwspinlock with timeout limit
173 * @hwlock: the hwspinlock to be locked
174 * @timeout: timeout value in msecs
175 * @mode: mode which controls whether local interrupts are disabled or not
176 * @flags: a pointer to where the caller's interrupt state will be saved at (if
177 * requested)
178 *
179 * This function locks the given @hwlock. If the @hwlock
180 * is already taken, the function will busy loop waiting for it to
181 * be released, but give up after @timeout msecs have elapsed.
182 *
183 * Caution: If the mode is HWLOCK_RAW, that means user must protect the routine
184 * of getting hardware lock with mutex or spinlock. Since in some scenarios,
185 * user need some time-consuming or sleepable operations under the hardware
186 * lock, they need one sleepable lock (like mutex) to protect the operations.
187 *
188 * If the mode is HWLOCK_IN_ATOMIC (called from an atomic context) the timeout
189 * is handled with busy-waiting delays, hence shall not exceed few msecs.
190 *
191 * If the mode is neither HWLOCK_IN_ATOMIC nor HWLOCK_RAW, upon a successful
192 * return from this function, preemption (and possibly interrupts) is disabled,
193 * so the caller must not sleep, and is advised to release the hwspinlock as
194 * soon as possible. This is required in order to minimize remote cores polling
195 * on the hardware interconnect.
196 *
197 * The user decides whether local interrupts are disabled or not, and if yes,
198 * whether he wants their previous state to be saved. It is up to the user
199 * to choose the appropriate @mode of operation, exactly the same way users
200 * should decide between spin_lock, spin_lock_irq and spin_lock_irqsave.
201 *
202 * Returns 0 when the @hwlock was successfully taken, and an appropriate
203 * error code otherwise (most notably -ETIMEDOUT if the @hwlock is still
204 * busy after @timeout msecs). The function will never sleep.
205 */
206int __hwspin_lock_timeout(struct hwspinlock *hwlock, unsigned int to,
207 int mode, unsigned long *flags)
208{
209 int ret;
210 unsigned long expire, atomic_delay = 0;
211
212 expire = msecs_to_jiffies(to) + jiffies;
213
214 for (;;) {
215 /* Try to take the hwspinlock */
216 ret = __hwspin_trylock(hwlock, mode, flags);
217 if (ret != -EBUSY)
218 break;
219
220 /*
221 * The lock is already taken, let's check if the user wants
222 * us to try again
223 */
224 if (mode == HWLOCK_IN_ATOMIC) {
225 udelay(HWSPINLOCK_RETRY_DELAY_US);
226 atomic_delay += HWSPINLOCK_RETRY_DELAY_US;
227 if (atomic_delay > to * 1000)
228 return -ETIMEDOUT;
229 } else {
230 if (time_is_before_eq_jiffies(expire))
231 return -ETIMEDOUT;
232 }
233
234 /*
235 * Allow platform-specific relax handlers to prevent
236 * hogging the interconnect (no sleeping, though)
237 */
238 if (hwlock->bank->ops->relax)
239 hwlock->bank->ops->relax(hwlock);
240 }
241
242 return ret;
243}
244EXPORT_SYMBOL_GPL(__hwspin_lock_timeout);
245
246/**
247 * __hwspin_unlock() - unlock a specific hwspinlock
248 * @hwlock: a previously-acquired hwspinlock which we want to unlock
249 * @mode: controls whether local interrupts needs to be restored or not
250 * @flags: previous caller's interrupt state to restore (if requested)
251 *
252 * This function will unlock a specific hwspinlock, enable preemption and
253 * (possibly) enable interrupts or restore their previous state.
254 * @hwlock must be already locked before calling this function: it is a bug
255 * to call unlock on a @hwlock that is already unlocked.
256 *
257 * The user decides whether local interrupts should be enabled or not, and
258 * if yes, whether he wants their previous state to be restored. It is up
259 * to the user to choose the appropriate @mode of operation, exactly the
260 * same way users decide between spin_unlock, spin_unlock_irq and
261 * spin_unlock_irqrestore.
262 *
263 * The function will never sleep.
264 */
265void __hwspin_unlock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
266{
267 if (WARN_ON(!hwlock || (!flags && mode == HWLOCK_IRQSTATE)))
268 return;
269
270 /*
271 * We must make sure that memory operations (both reads and writes),
272 * done before unlocking the hwspinlock, will not be reordered
273 * after the lock is released.
274 *
275 * That's the purpose of this explicit memory barrier.
276 *
277 * Note: the memory barrier induced by the spin_unlock below is too
278 * late; the other core is going to access memory soon after it will
279 * take the hwspinlock, and by then we want to be sure our memory
280 * operations are already observable.
281 */
282 mb();
283
284 hwlock->bank->ops->unlock(hwlock);
285
286 /* Undo the spin_trylock{_irq, _irqsave} called while locking */
287 switch (mode) {
288 case HWLOCK_IRQSTATE:
289 spin_unlock_irqrestore(&hwlock->lock, *flags);
290 break;
291 case HWLOCK_IRQ:
292 spin_unlock_irq(&hwlock->lock);
293 break;
294 case HWLOCK_RAW:
295 case HWLOCK_IN_ATOMIC:
296 /* Nothing to do */
297 break;
298 default:
299 spin_unlock(&hwlock->lock);
300 break;
301 }
302}
303EXPORT_SYMBOL_GPL(__hwspin_unlock);
304
305/**
306 * of_hwspin_lock_simple_xlate - translate hwlock_spec to return a lock id
307 * @bank: the hwspinlock device bank
308 * @hwlock_spec: hwlock specifier as found in the device tree
309 *
310 * This is a simple translation function, suitable for hwspinlock platform
311 * drivers that only has a lock specifier length of 1.
312 *
313 * Returns a relative index of the lock within a specified bank on success,
314 * or -EINVAL on invalid specifier cell count.
315 */
316static inline int
317of_hwspin_lock_simple_xlate(const struct of_phandle_args *hwlock_spec)
318{
319 if (WARN_ON(hwlock_spec->args_count != 1))
320 return -EINVAL;
321
322 return hwlock_spec->args[0];
323}
324
325/**
326 * of_hwspin_lock_get_id() - get lock id for an OF phandle-based specific lock
327 * @np: device node from which to request the specific hwlock
328 * @index: index of the hwlock in the list of values
329 *
330 * This function provides a means for DT users of the hwspinlock module to
331 * get the global lock id of a specific hwspinlock using the phandle of the
332 * hwspinlock device, so that it can be requested using the normal
333 * hwspin_lock_request_specific() API.
334 *
335 * Returns the global lock id number on success, -EPROBE_DEFER if the hwspinlock
336 * device is not yet registered, -EINVAL on invalid args specifier value or an
337 * appropriate error as returned from the OF parsing of the DT client node.
338 */
339int of_hwspin_lock_get_id(struct device_node *np, int index)
340{
341 struct of_phandle_args args;
342 struct hwspinlock *hwlock;
343 struct radix_tree_iter iter;
344 void **slot;
345 int id;
346 int ret;
347
348 ret = of_parse_phandle_with_args(np, "hwlocks", "#hwlock-cells", index,
349 &args);
350 if (ret)
351 return ret;
352
353 if (!of_device_is_available(args.np)) {
354 ret = -ENOENT;
355 goto out;
356 }
357
358 /* Find the hwspinlock device: we need its base_id */
359 ret = -EPROBE_DEFER;
360 rcu_read_lock();
361 radix_tree_for_each_slot(slot, &hwspinlock_tree, &iter, 0) {
362 hwlock = radix_tree_deref_slot(slot);
363 if (unlikely(!hwlock))
364 continue;
365 if (radix_tree_deref_retry(hwlock)) {
366 slot = radix_tree_iter_retry(&iter);
367 continue;
368 }
369
370 if (hwlock->bank->dev->of_node == args.np) {
371 ret = 0;
372 break;
373 }
374 }
375 rcu_read_unlock();
376 if (ret < 0)
377 goto out;
378
379 id = of_hwspin_lock_simple_xlate(&args);
380 if (id < 0 || id >= hwlock->bank->num_locks) {
381 ret = -EINVAL;
382 goto out;
383 }
384 id += hwlock->bank->base_id;
385
386out:
387 of_node_put(args.np);
388 return ret ? ret : id;
389}
390EXPORT_SYMBOL_GPL(of_hwspin_lock_get_id);
391
392/**
393 * of_hwspin_lock_get_id_byname() - get lock id for an specified hwlock name
394 * @np: device node from which to request the specific hwlock
395 * @name: hwlock name
396 *
397 * This function provides a means for DT users of the hwspinlock module to
398 * get the global lock id of a specific hwspinlock using the specified name of
399 * the hwspinlock device, so that it can be requested using the normal
400 * hwspin_lock_request_specific() API.
401 *
402 * Returns the global lock id number on success, -EPROBE_DEFER if the hwspinlock
403 * device is not yet registered, -EINVAL on invalid args specifier value or an
404 * appropriate error as returned from the OF parsing of the DT client node.
405 */
406int of_hwspin_lock_get_id_byname(struct device_node *np, const char *name)
407{
408 int index;
409
410 if (!name)
411 return -EINVAL;
412
413 index = of_property_match_string(np, "hwlock-names", name);
414 if (index < 0)
415 return index;
416
417 return of_hwspin_lock_get_id(np, index);
418}
419EXPORT_SYMBOL_GPL(of_hwspin_lock_get_id_byname);
420
421static int hwspin_lock_register_single(struct hwspinlock *hwlock, int id)
422{
423 struct hwspinlock *tmp;
424 int ret;
425
426 mutex_lock(&hwspinlock_tree_lock);
427
428 ret = radix_tree_insert(&hwspinlock_tree, id, hwlock);
429 if (ret) {
430 if (ret == -EEXIST)
431 pr_err("hwspinlock id %d already exists!\n", id);
432 goto out;
433 }
434
435 /* mark this hwspinlock as available */
436 tmp = radix_tree_tag_set(&hwspinlock_tree, id, HWSPINLOCK_UNUSED);
437
438 /* self-sanity check which should never fail */
439 WARN_ON(tmp != hwlock);
440
441out:
442 mutex_unlock(&hwspinlock_tree_lock);
443 return 0;
444}
445
446static struct hwspinlock *hwspin_lock_unregister_single(unsigned int id)
447{
448 struct hwspinlock *hwlock = NULL;
449 int ret;
450
451 mutex_lock(&hwspinlock_tree_lock);
452
453 /* make sure the hwspinlock is not in use (tag is set) */
454 ret = radix_tree_tag_get(&hwspinlock_tree, id, HWSPINLOCK_UNUSED);
455 if (ret == 0) {
456 pr_err("hwspinlock %d still in use (or not present)\n", id);
457 goto out;
458 }
459
460 hwlock = radix_tree_delete(&hwspinlock_tree, id);
461 if (!hwlock) {
462 pr_err("failed to delete hwspinlock %d\n", id);
463 goto out;
464 }
465
466out:
467 mutex_unlock(&hwspinlock_tree_lock);
468 return hwlock;
469}
470
471/**
472 * hwspin_lock_register() - register a new hw spinlock device
473 * @bank: the hwspinlock device, which usually provides numerous hw locks
474 * @dev: the backing device
475 * @ops: hwspinlock handlers for this device
476 * @base_id: id of the first hardware spinlock in this bank
477 * @num_locks: number of hwspinlocks provided by this device
478 *
479 * This function should be called from the underlying platform-specific
480 * implementation, to register a new hwspinlock device instance.
481 *
482 * Should be called from a process context (might sleep)
483 *
484 * Returns 0 on success, or an appropriate error code on failure
485 */
486int hwspin_lock_register(struct hwspinlock_device *bank, struct device *dev,
487 const struct hwspinlock_ops *ops, int base_id, int num_locks)
488{
489 struct hwspinlock *hwlock;
490 int ret = 0, i;
491
492 if (!bank || !ops || !dev || !num_locks || !ops->trylock ||
493 !ops->unlock) {
494 pr_err("invalid parameters\n");
495 return -EINVAL;
496 }
497
498 bank->dev = dev;
499 bank->ops = ops;
500 bank->base_id = base_id;
501 bank->num_locks = num_locks;
502
503 for (i = 0; i < num_locks; i++) {
504 hwlock = &bank->lock[i];
505
506 spin_lock_init(&hwlock->lock);
507 hwlock->bank = bank;
508
509 ret = hwspin_lock_register_single(hwlock, base_id + i);
510 if (ret)
511 goto reg_failed;
512 }
513
514 return 0;
515
516reg_failed:
517 while (--i >= 0)
518 hwspin_lock_unregister_single(base_id + i);
519 return ret;
520}
521EXPORT_SYMBOL_GPL(hwspin_lock_register);
522
523/**
524 * hwspin_lock_unregister() - unregister an hw spinlock device
525 * @bank: the hwspinlock device, which usually provides numerous hw locks
526 *
527 * This function should be called from the underlying platform-specific
528 * implementation, to unregister an existing (and unused) hwspinlock.
529 *
530 * Should be called from a process context (might sleep)
531 *
532 * Returns 0 on success, or an appropriate error code on failure
533 */
534int hwspin_lock_unregister(struct hwspinlock_device *bank)
535{
536 struct hwspinlock *hwlock, *tmp;
537 int i;
538
539 for (i = 0; i < bank->num_locks; i++) {
540 hwlock = &bank->lock[i];
541
542 tmp = hwspin_lock_unregister_single(bank->base_id + i);
543 if (!tmp)
544 return -EBUSY;
545
546 /* self-sanity check that should never fail */
547 WARN_ON(tmp != hwlock);
548 }
549
550 return 0;
551}
552EXPORT_SYMBOL_GPL(hwspin_lock_unregister);
553
554static void devm_hwspin_lock_unreg(struct device *dev, void *res)
555{
556 hwspin_lock_unregister(*(struct hwspinlock_device **)res);
557}
558
559static int devm_hwspin_lock_device_match(struct device *dev, void *res,
560 void *data)
561{
562 struct hwspinlock_device **bank = res;
563
564 if (WARN_ON(!bank || !*bank))
565 return 0;
566
567 return *bank == data;
568}
569
570/**
571 * devm_hwspin_lock_unregister() - unregister an hw spinlock device for
572 * a managed device
573 * @dev: the backing device
574 * @bank: the hwspinlock device, which usually provides numerous hw locks
575 *
576 * This function should be called from the underlying platform-specific
577 * implementation, to unregister an existing (and unused) hwspinlock.
578 *
579 * Should be called from a process context (might sleep)
580 *
581 * Returns 0 on success, or an appropriate error code on failure
582 */
583int devm_hwspin_lock_unregister(struct device *dev,
584 struct hwspinlock_device *bank)
585{
586 int ret;
587
588 ret = devres_release(dev, devm_hwspin_lock_unreg,
589 devm_hwspin_lock_device_match, bank);
590 WARN_ON(ret);
591
592 return ret;
593}
594EXPORT_SYMBOL_GPL(devm_hwspin_lock_unregister);
595
596/**
597 * devm_hwspin_lock_register() - register a new hw spinlock device for
598 * a managed device
599 * @dev: the backing device
600 * @bank: the hwspinlock device, which usually provides numerous hw locks
601 * @ops: hwspinlock handlers for this device
602 * @base_id: id of the first hardware spinlock in this bank
603 * @num_locks: number of hwspinlocks provided by this device
604 *
605 * This function should be called from the underlying platform-specific
606 * implementation, to register a new hwspinlock device instance.
607 *
608 * Should be called from a process context (might sleep)
609 *
610 * Returns 0 on success, or an appropriate error code on failure
611 */
612int devm_hwspin_lock_register(struct device *dev,
613 struct hwspinlock_device *bank,
614 const struct hwspinlock_ops *ops,
615 int base_id, int num_locks)
616{
617 struct hwspinlock_device **ptr;
618 int ret;
619
620 ptr = devres_alloc(devm_hwspin_lock_unreg, sizeof(*ptr), GFP_KERNEL);
621 if (!ptr)
622 return -ENOMEM;
623
624 ret = hwspin_lock_register(bank, dev, ops, base_id, num_locks);
625 if (!ret) {
626 *ptr = bank;
627 devres_add(dev, ptr);
628 } else {
629 devres_free(ptr);
630 }
631
632 return ret;
633}
634EXPORT_SYMBOL_GPL(devm_hwspin_lock_register);
635
636/**
637 * __hwspin_lock_request() - tag an hwspinlock as used and power it up
638 *
639 * This is an internal function that prepares an hwspinlock instance
640 * before it is given to the user. The function assumes that
641 * hwspinlock_tree_lock is taken.
642 *
643 * Returns 0 or positive to indicate success, and a negative value to
644 * indicate an error (with the appropriate error code)
645 */
646static int __hwspin_lock_request(struct hwspinlock *hwlock)
647{
648 struct device *dev = hwlock->bank->dev;
649 struct hwspinlock *tmp;
650 int ret;
651
652 /* prevent underlying implementation from being removed */
653 if (!try_module_get(dev->driver->owner)) {
654 dev_err(dev, "%s: can't get owner\n", __func__);
655 return -EINVAL;
656 }
657
658 /* notify PM core that power is now needed */
659 ret = pm_runtime_get_sync(dev);
660 if (ret < 0 && ret != -EACCES) {
661 dev_err(dev, "%s: can't power on device\n", __func__);
662 pm_runtime_put_noidle(dev);
663 module_put(dev->driver->owner);
664 return ret;
665 }
666
667 ret = 0;
668
669 /* mark hwspinlock as used, should not fail */
670 tmp = radix_tree_tag_clear(&hwspinlock_tree, hwlock_to_id(hwlock),
671 HWSPINLOCK_UNUSED);
672
673 /* self-sanity check that should never fail */
674 WARN_ON(tmp != hwlock);
675
676 return ret;
677}
678
679/**
680 * hwspin_lock_get_id() - retrieve id number of a given hwspinlock
681 * @hwlock: a valid hwspinlock instance
682 *
683 * Returns the id number of a given @hwlock, or -EINVAL if @hwlock is invalid.
684 */
685int hwspin_lock_get_id(struct hwspinlock *hwlock)
686{
687 if (!hwlock) {
688 pr_err("invalid hwlock\n");
689 return -EINVAL;
690 }
691
692 return hwlock_to_id(hwlock);
693}
694EXPORT_SYMBOL_GPL(hwspin_lock_get_id);
695
696/**
697 * hwspin_lock_request() - request an hwspinlock
698 *
699 * This function should be called by users of the hwspinlock device,
700 * in order to dynamically assign them an unused hwspinlock.
701 * Usually the user of this lock will then have to communicate the lock's id
702 * to the remote core before it can be used for synchronization (to get the
703 * id of a given hwlock, use hwspin_lock_get_id()).
704 *
705 * Should be called from a process context (might sleep)
706 *
707 * Returns the address of the assigned hwspinlock, or NULL on error
708 */
709struct hwspinlock *hwspin_lock_request(void)
710{
711 struct hwspinlock *hwlock;
712 int ret;
713
714 mutex_lock(&hwspinlock_tree_lock);
715
716 /* look for an unused lock */
717 ret = radix_tree_gang_lookup_tag(&hwspinlock_tree, (void **)&hwlock,
718 0, 1, HWSPINLOCK_UNUSED);
719 if (ret == 0) {
720 pr_warn("a free hwspinlock is not available\n");
721 hwlock = NULL;
722 goto out;
723 }
724
725 /* sanity check that should never fail */
726 WARN_ON(ret > 1);
727
728 /* mark as used and power up */
729 ret = __hwspin_lock_request(hwlock);
730 if (ret < 0)
731 hwlock = NULL;
732
733out:
734 mutex_unlock(&hwspinlock_tree_lock);
735 return hwlock;
736}
737EXPORT_SYMBOL_GPL(hwspin_lock_request);
738
739/**
740 * hwspin_lock_request_specific() - request for a specific hwspinlock
741 * @id: index of the specific hwspinlock that is requested
742 *
743 * This function should be called by users of the hwspinlock module,
744 * in order to assign them a specific hwspinlock.
745 * Usually early board code will be calling this function in order to
746 * reserve specific hwspinlock ids for predefined purposes.
747 *
748 * Should be called from a process context (might sleep)
749 *
750 * Returns the address of the assigned hwspinlock, or NULL on error
751 */
752struct hwspinlock *hwspin_lock_request_specific(unsigned int id)
753{
754 struct hwspinlock *hwlock;
755 int ret;
756
757 mutex_lock(&hwspinlock_tree_lock);
758
759 /* make sure this hwspinlock exists */
760 hwlock = radix_tree_lookup(&hwspinlock_tree, id);
761 if (!hwlock) {
762 pr_warn("hwspinlock %u does not exist\n", id);
763 goto out;
764 }
765
766 /* sanity check (this shouldn't happen) */
767 WARN_ON(hwlock_to_id(hwlock) != id);
768
769 /* make sure this hwspinlock is unused */
770 ret = radix_tree_tag_get(&hwspinlock_tree, id, HWSPINLOCK_UNUSED);
771 if (ret == 0) {
772 pr_warn("hwspinlock %u is already in use\n", id);
773 hwlock = NULL;
774 goto out;
775 }
776
777 /* mark as used and power up */
778 ret = __hwspin_lock_request(hwlock);
779 if (ret < 0)
780 hwlock = NULL;
781
782out:
783 mutex_unlock(&hwspinlock_tree_lock);
784 return hwlock;
785}
786EXPORT_SYMBOL_GPL(hwspin_lock_request_specific);
787
788/**
789 * hwspin_lock_free() - free a specific hwspinlock
790 * @hwlock: the specific hwspinlock to free
791 *
792 * This function mark @hwlock as free again.
793 * Should only be called with an @hwlock that was retrieved from
794 * an earlier call to hwspin_lock_request{_specific}.
795 *
796 * Should be called from a process context (might sleep)
797 *
798 * Returns 0 on success, or an appropriate error code on failure
799 */
800int hwspin_lock_free(struct hwspinlock *hwlock)
801{
802 struct device *dev;
803 struct hwspinlock *tmp;
804 int ret;
805
806 if (!hwlock) {
807 pr_err("invalid hwlock\n");
808 return -EINVAL;
809 }
810
811 dev = hwlock->bank->dev;
812 mutex_lock(&hwspinlock_tree_lock);
813
814 /* make sure the hwspinlock is used */
815 ret = radix_tree_tag_get(&hwspinlock_tree, hwlock_to_id(hwlock),
816 HWSPINLOCK_UNUSED);
817 if (ret == 1) {
818 dev_err(dev, "%s: hwlock is already free\n", __func__);
819 dump_stack();
820 ret = -EINVAL;
821 goto out;
822 }
823
824 /* notify the underlying device that power is not needed */
825 pm_runtime_put(dev);
826
827 /* mark this hwspinlock as available */
828 tmp = radix_tree_tag_set(&hwspinlock_tree, hwlock_to_id(hwlock),
829 HWSPINLOCK_UNUSED);
830
831 /* sanity check (this shouldn't happen) */
832 WARN_ON(tmp != hwlock);
833
834 module_put(dev->driver->owner);
835
836out:
837 mutex_unlock(&hwspinlock_tree_lock);
838 return ret;
839}
840EXPORT_SYMBOL_GPL(hwspin_lock_free);
841
842static int devm_hwspin_lock_match(struct device *dev, void *res, void *data)
843{
844 struct hwspinlock **hwlock = res;
845
846 if (WARN_ON(!hwlock || !*hwlock))
847 return 0;
848
849 return *hwlock == data;
850}
851
852static void devm_hwspin_lock_release(struct device *dev, void *res)
853{
854 hwspin_lock_free(*(struct hwspinlock **)res);
855}
856
857/**
858 * devm_hwspin_lock_free() - free a specific hwspinlock for a managed device
859 * @dev: the device to free the specific hwspinlock
860 * @hwlock: the specific hwspinlock to free
861 *
862 * This function mark @hwlock as free again.
863 * Should only be called with an @hwlock that was retrieved from
864 * an earlier call to hwspin_lock_request{_specific}.
865 *
866 * Should be called from a process context (might sleep)
867 *
868 * Returns 0 on success, or an appropriate error code on failure
869 */
870int devm_hwspin_lock_free(struct device *dev, struct hwspinlock *hwlock)
871{
872 int ret;
873
874 ret = devres_release(dev, devm_hwspin_lock_release,
875 devm_hwspin_lock_match, hwlock);
876 WARN_ON(ret);
877
878 return ret;
879}
880EXPORT_SYMBOL_GPL(devm_hwspin_lock_free);
881
882/**
883 * devm_hwspin_lock_request() - request an hwspinlock for a managed device
884 * @dev: the device to request an hwspinlock
885 *
886 * This function should be called by users of the hwspinlock device,
887 * in order to dynamically assign them an unused hwspinlock.
888 * Usually the user of this lock will then have to communicate the lock's id
889 * to the remote core before it can be used for synchronization (to get the
890 * id of a given hwlock, use hwspin_lock_get_id()).
891 *
892 * Should be called from a process context (might sleep)
893 *
894 * Returns the address of the assigned hwspinlock, or NULL on error
895 */
896struct hwspinlock *devm_hwspin_lock_request(struct device *dev)
897{
898 struct hwspinlock **ptr, *hwlock;
899
900 ptr = devres_alloc(devm_hwspin_lock_release, sizeof(*ptr), GFP_KERNEL);
901 if (!ptr)
902 return NULL;
903
904 hwlock = hwspin_lock_request();
905 if (hwlock) {
906 *ptr = hwlock;
907 devres_add(dev, ptr);
908 } else {
909 devres_free(ptr);
910 }
911
912 return hwlock;
913}
914EXPORT_SYMBOL_GPL(devm_hwspin_lock_request);
915
916/**
917 * devm_hwspin_lock_request_specific() - request for a specific hwspinlock for
918 * a managed device
919 * @dev: the device to request the specific hwspinlock
920 * @id: index of the specific hwspinlock that is requested
921 *
922 * This function should be called by users of the hwspinlock module,
923 * in order to assign them a specific hwspinlock.
924 * Usually early board code will be calling this function in order to
925 * reserve specific hwspinlock ids for predefined purposes.
926 *
927 * Should be called from a process context (might sleep)
928 *
929 * Returns the address of the assigned hwspinlock, or NULL on error
930 */
931struct hwspinlock *devm_hwspin_lock_request_specific(struct device *dev,
932 unsigned int id)
933{
934 struct hwspinlock **ptr, *hwlock;
935
936 ptr = devres_alloc(devm_hwspin_lock_release, sizeof(*ptr), GFP_KERNEL);
937 if (!ptr)
938 return NULL;
939
940 hwlock = hwspin_lock_request_specific(id);
941 if (hwlock) {
942 *ptr = hwlock;
943 devres_add(dev, ptr);
944 } else {
945 devres_free(ptr);
946 }
947
948 return hwlock;
949}
950EXPORT_SYMBOL_GPL(devm_hwspin_lock_request_specific);
951
952MODULE_LICENSE("GPL v2");
953MODULE_DESCRIPTION("Hardware spinlock interface");
954MODULE_AUTHOR("Ohad Ben-Cohen <ohad@wizery.com>");
1/*
2 * Hardware spinlock framework
3 *
4 * Copyright (C) 2010 Texas Instruments Incorporated - http://www.ti.com
5 *
6 * Contact: Ohad Ben-Cohen <ohad@wizery.com>
7 *
8 * This program is free software; you can redistribute it and/or modify it
9 * under the terms of the GNU General Public License version 2 as published
10 * by the Free Software Foundation.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 */
17
18#define pr_fmt(fmt) "%s: " fmt, __func__
19
20#include <linux/kernel.h>
21#include <linux/module.h>
22#include <linux/spinlock.h>
23#include <linux/types.h>
24#include <linux/err.h>
25#include <linux/jiffies.h>
26#include <linux/radix-tree.h>
27#include <linux/hwspinlock.h>
28#include <linux/pm_runtime.h>
29#include <linux/mutex.h>
30
31#include "hwspinlock_internal.h"
32
33/* radix tree tags */
34#define HWSPINLOCK_UNUSED (0) /* tags an hwspinlock as unused */
35
36/*
37 * A radix tree is used to maintain the available hwspinlock instances.
38 * The tree associates hwspinlock pointers with their integer key id,
39 * and provides easy-to-use API which makes the hwspinlock core code simple
40 * and easy to read.
41 *
42 * Radix trees are quick on lookups, and reasonably efficient in terms of
43 * storage, especially with high density usages such as this framework
44 * requires (a continuous range of integer keys, beginning with zero, is
45 * used as the ID's of the hwspinlock instances).
46 *
47 * The radix tree API supports tagging items in the tree, which this
48 * framework uses to mark unused hwspinlock instances (see the
49 * HWSPINLOCK_UNUSED tag above). As a result, the process of querying the
50 * tree, looking for an unused hwspinlock instance, is now reduced to a
51 * single radix tree API call.
52 */
53static RADIX_TREE(hwspinlock_tree, GFP_KERNEL);
54
55/*
56 * Synchronization of access to the tree is achieved using this mutex,
57 * as the radix-tree API requires that users provide all synchronisation.
58 * A mutex is needed because we're using non-atomic radix tree allocations.
59 */
60static DEFINE_MUTEX(hwspinlock_tree_lock);
61
62
63/**
64 * __hwspin_trylock() - attempt to lock a specific hwspinlock
65 * @hwlock: an hwspinlock which we want to trylock
66 * @mode: controls whether local interrupts are disabled or not
67 * @flags: a pointer where the caller's interrupt state will be saved at (if
68 * requested)
69 *
70 * This function attempts to lock an hwspinlock, and will immediately
71 * fail if the hwspinlock is already taken.
72 *
73 * Upon a successful return from this function, preemption (and possibly
74 * interrupts) is disabled, so the caller must not sleep, and is advised to
75 * release the hwspinlock as soon as possible. This is required in order to
76 * minimize remote cores polling on the hardware interconnect.
77 *
78 * The user decides whether local interrupts are disabled or not, and if yes,
79 * whether he wants their previous state to be saved. It is up to the user
80 * to choose the appropriate @mode of operation, exactly the same way users
81 * should decide between spin_trylock, spin_trylock_irq and
82 * spin_trylock_irqsave.
83 *
84 * Returns 0 if we successfully locked the hwspinlock or -EBUSY if
85 * the hwspinlock was already taken.
86 * This function will never sleep.
87 */
88int __hwspin_trylock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
89{
90 int ret;
91
92 BUG_ON(!hwlock);
93 BUG_ON(!flags && mode == HWLOCK_IRQSTATE);
94
95 /*
96 * This spin_lock{_irq, _irqsave} serves three purposes:
97 *
98 * 1. Disable preemption, in order to minimize the period of time
99 * in which the hwspinlock is taken. This is important in order
100 * to minimize the possible polling on the hardware interconnect
101 * by a remote user of this lock.
102 * 2. Make the hwspinlock SMP-safe (so we can take it from
103 * additional contexts on the local host).
104 * 3. Ensure that in_atomic/might_sleep checks catch potential
105 * problems with hwspinlock usage (e.g. scheduler checks like
106 * 'scheduling while atomic' etc.)
107 */
108 if (mode == HWLOCK_IRQSTATE)
109 ret = spin_trylock_irqsave(&hwlock->lock, *flags);
110 else if (mode == HWLOCK_IRQ)
111 ret = spin_trylock_irq(&hwlock->lock);
112 else
113 ret = spin_trylock(&hwlock->lock);
114
115 /* is lock already taken by another context on the local cpu ? */
116 if (!ret)
117 return -EBUSY;
118
119 /* try to take the hwspinlock device */
120 ret = hwlock->bank->ops->trylock(hwlock);
121
122 /* if hwlock is already taken, undo spin_trylock_* and exit */
123 if (!ret) {
124 if (mode == HWLOCK_IRQSTATE)
125 spin_unlock_irqrestore(&hwlock->lock, *flags);
126 else if (mode == HWLOCK_IRQ)
127 spin_unlock_irq(&hwlock->lock);
128 else
129 spin_unlock(&hwlock->lock);
130
131 return -EBUSY;
132 }
133
134 /*
135 * We can be sure the other core's memory operations
136 * are observable to us only _after_ we successfully take
137 * the hwspinlock, and we must make sure that subsequent memory
138 * operations (both reads and writes) will not be reordered before
139 * we actually took the hwspinlock.
140 *
141 * Note: the implicit memory barrier of the spinlock above is too
142 * early, so we need this additional explicit memory barrier.
143 */
144 mb();
145
146 return 0;
147}
148EXPORT_SYMBOL_GPL(__hwspin_trylock);
149
150/**
151 * __hwspin_lock_timeout() - lock an hwspinlock with timeout limit
152 * @hwlock: the hwspinlock to be locked
153 * @timeout: timeout value in msecs
154 * @mode: mode which controls whether local interrupts are disabled or not
155 * @flags: a pointer to where the caller's interrupt state will be saved at (if
156 * requested)
157 *
158 * This function locks the given @hwlock. If the @hwlock
159 * is already taken, the function will busy loop waiting for it to
160 * be released, but give up after @timeout msecs have elapsed.
161 *
162 * Upon a successful return from this function, preemption is disabled
163 * (and possibly local interrupts, too), so the caller must not sleep,
164 * and is advised to release the hwspinlock as soon as possible.
165 * This is required in order to minimize remote cores polling on the
166 * hardware interconnect.
167 *
168 * The user decides whether local interrupts are disabled or not, and if yes,
169 * whether he wants their previous state to be saved. It is up to the user
170 * to choose the appropriate @mode of operation, exactly the same way users
171 * should decide between spin_lock, spin_lock_irq and spin_lock_irqsave.
172 *
173 * Returns 0 when the @hwlock was successfully taken, and an appropriate
174 * error code otherwise (most notably -ETIMEDOUT if the @hwlock is still
175 * busy after @timeout msecs). The function will never sleep.
176 */
177int __hwspin_lock_timeout(struct hwspinlock *hwlock, unsigned int to,
178 int mode, unsigned long *flags)
179{
180 int ret;
181 unsigned long expire;
182
183 expire = msecs_to_jiffies(to) + jiffies;
184
185 for (;;) {
186 /* Try to take the hwspinlock */
187 ret = __hwspin_trylock(hwlock, mode, flags);
188 if (ret != -EBUSY)
189 break;
190
191 /*
192 * The lock is already taken, let's check if the user wants
193 * us to try again
194 */
195 if (time_is_before_eq_jiffies(expire))
196 return -ETIMEDOUT;
197
198 /*
199 * Allow platform-specific relax handlers to prevent
200 * hogging the interconnect (no sleeping, though)
201 */
202 if (hwlock->bank->ops->relax)
203 hwlock->bank->ops->relax(hwlock);
204 }
205
206 return ret;
207}
208EXPORT_SYMBOL_GPL(__hwspin_lock_timeout);
209
210/**
211 * __hwspin_unlock() - unlock a specific hwspinlock
212 * @hwlock: a previously-acquired hwspinlock which we want to unlock
213 * @mode: controls whether local interrupts needs to be restored or not
214 * @flags: previous caller's interrupt state to restore (if requested)
215 *
216 * This function will unlock a specific hwspinlock, enable preemption and
217 * (possibly) enable interrupts or restore their previous state.
218 * @hwlock must be already locked before calling this function: it is a bug
219 * to call unlock on a @hwlock that is already unlocked.
220 *
221 * The user decides whether local interrupts should be enabled or not, and
222 * if yes, whether he wants their previous state to be restored. It is up
223 * to the user to choose the appropriate @mode of operation, exactly the
224 * same way users decide between spin_unlock, spin_unlock_irq and
225 * spin_unlock_irqrestore.
226 *
227 * The function will never sleep.
228 */
229void __hwspin_unlock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
230{
231 BUG_ON(!hwlock);
232 BUG_ON(!flags && mode == HWLOCK_IRQSTATE);
233
234 /*
235 * We must make sure that memory operations (both reads and writes),
236 * done before unlocking the hwspinlock, will not be reordered
237 * after the lock is released.
238 *
239 * That's the purpose of this explicit memory barrier.
240 *
241 * Note: the memory barrier induced by the spin_unlock below is too
242 * late; the other core is going to access memory soon after it will
243 * take the hwspinlock, and by then we want to be sure our memory
244 * operations are already observable.
245 */
246 mb();
247
248 hwlock->bank->ops->unlock(hwlock);
249
250 /* Undo the spin_trylock{_irq, _irqsave} called while locking */
251 if (mode == HWLOCK_IRQSTATE)
252 spin_unlock_irqrestore(&hwlock->lock, *flags);
253 else if (mode == HWLOCK_IRQ)
254 spin_unlock_irq(&hwlock->lock);
255 else
256 spin_unlock(&hwlock->lock);
257}
258EXPORT_SYMBOL_GPL(__hwspin_unlock);
259
260static int hwspin_lock_register_single(struct hwspinlock *hwlock, int id)
261{
262 struct hwspinlock *tmp;
263 int ret;
264
265 mutex_lock(&hwspinlock_tree_lock);
266
267 ret = radix_tree_insert(&hwspinlock_tree, id, hwlock);
268 if (ret) {
269 if (ret == -EEXIST)
270 pr_err("hwspinlock id %d already exists!\n", id);
271 goto out;
272 }
273
274 /* mark this hwspinlock as available */
275 tmp = radix_tree_tag_set(&hwspinlock_tree, id, HWSPINLOCK_UNUSED);
276
277 /* self-sanity check which should never fail */
278 WARN_ON(tmp != hwlock);
279
280out:
281 mutex_unlock(&hwspinlock_tree_lock);
282 return 0;
283}
284
285static struct hwspinlock *hwspin_lock_unregister_single(unsigned int id)
286{
287 struct hwspinlock *hwlock = NULL;
288 int ret;
289
290 mutex_lock(&hwspinlock_tree_lock);
291
292 /* make sure the hwspinlock is not in use (tag is set) */
293 ret = radix_tree_tag_get(&hwspinlock_tree, id, HWSPINLOCK_UNUSED);
294 if (ret == 0) {
295 pr_err("hwspinlock %d still in use (or not present)\n", id);
296 goto out;
297 }
298
299 hwlock = radix_tree_delete(&hwspinlock_tree, id);
300 if (!hwlock) {
301 pr_err("failed to delete hwspinlock %d\n", id);
302 goto out;
303 }
304
305out:
306 mutex_unlock(&hwspinlock_tree_lock);
307 return hwlock;
308}
309
310/**
311 * hwspin_lock_register() - register a new hw spinlock device
312 * @bank: the hwspinlock device, which usually provides numerous hw locks
313 * @dev: the backing device
314 * @ops: hwspinlock handlers for this device
315 * @base_id: id of the first hardware spinlock in this bank
316 * @num_locks: number of hwspinlocks provided by this device
317 *
318 * This function should be called from the underlying platform-specific
319 * implementation, to register a new hwspinlock device instance.
320 *
321 * Should be called from a process context (might sleep)
322 *
323 * Returns 0 on success, or an appropriate error code on failure
324 */
325int hwspin_lock_register(struct hwspinlock_device *bank, struct device *dev,
326 const struct hwspinlock_ops *ops, int base_id, int num_locks)
327{
328 struct hwspinlock *hwlock;
329 int ret = 0, i;
330
331 if (!bank || !ops || !dev || !num_locks || !ops->trylock ||
332 !ops->unlock) {
333 pr_err("invalid parameters\n");
334 return -EINVAL;
335 }
336
337 bank->dev = dev;
338 bank->ops = ops;
339 bank->base_id = base_id;
340 bank->num_locks = num_locks;
341
342 for (i = 0; i < num_locks; i++) {
343 hwlock = &bank->lock[i];
344
345 spin_lock_init(&hwlock->lock);
346 hwlock->bank = bank;
347
348 ret = hwspin_lock_register_single(hwlock, base_id + i);
349 if (ret)
350 goto reg_failed;
351 }
352
353 return 0;
354
355reg_failed:
356 while (--i >= 0)
357 hwspin_lock_unregister_single(base_id + i);
358 return ret;
359}
360EXPORT_SYMBOL_GPL(hwspin_lock_register);
361
362/**
363 * hwspin_lock_unregister() - unregister an hw spinlock device
364 * @bank: the hwspinlock device, which usually provides numerous hw locks
365 *
366 * This function should be called from the underlying platform-specific
367 * implementation, to unregister an existing (and unused) hwspinlock.
368 *
369 * Should be called from a process context (might sleep)
370 *
371 * Returns 0 on success, or an appropriate error code on failure
372 */
373int hwspin_lock_unregister(struct hwspinlock_device *bank)
374{
375 struct hwspinlock *hwlock, *tmp;
376 int i;
377
378 for (i = 0; i < bank->num_locks; i++) {
379 hwlock = &bank->lock[i];
380
381 tmp = hwspin_lock_unregister_single(bank->base_id + i);
382 if (!tmp)
383 return -EBUSY;
384
385 /* self-sanity check that should never fail */
386 WARN_ON(tmp != hwlock);
387 }
388
389 return 0;
390}
391EXPORT_SYMBOL_GPL(hwspin_lock_unregister);
392
393/**
394 * __hwspin_lock_request() - tag an hwspinlock as used and power it up
395 *
396 * This is an internal function that prepares an hwspinlock instance
397 * before it is given to the user. The function assumes that
398 * hwspinlock_tree_lock is taken.
399 *
400 * Returns 0 or positive to indicate success, and a negative value to
401 * indicate an error (with the appropriate error code)
402 */
403static int __hwspin_lock_request(struct hwspinlock *hwlock)
404{
405 struct device *dev = hwlock->bank->dev;
406 struct hwspinlock *tmp;
407 int ret;
408
409 /* prevent underlying implementation from being removed */
410 if (!try_module_get(dev->driver->owner)) {
411 dev_err(dev, "%s: can't get owner\n", __func__);
412 return -EINVAL;
413 }
414
415 /* notify PM core that power is now needed */
416 ret = pm_runtime_get_sync(dev);
417 if (ret < 0) {
418 dev_err(dev, "%s: can't power on device\n", __func__);
419 return ret;
420 }
421
422 /* mark hwspinlock as used, should not fail */
423 tmp = radix_tree_tag_clear(&hwspinlock_tree, hwlock_to_id(hwlock),
424 HWSPINLOCK_UNUSED);
425
426 /* self-sanity check that should never fail */
427 WARN_ON(tmp != hwlock);
428
429 return ret;
430}
431
432/**
433 * hwspin_lock_get_id() - retrieve id number of a given hwspinlock
434 * @hwlock: a valid hwspinlock instance
435 *
436 * Returns the id number of a given @hwlock, or -EINVAL if @hwlock is invalid.
437 */
438int hwspin_lock_get_id(struct hwspinlock *hwlock)
439{
440 if (!hwlock) {
441 pr_err("invalid hwlock\n");
442 return -EINVAL;
443 }
444
445 return hwlock_to_id(hwlock);
446}
447EXPORT_SYMBOL_GPL(hwspin_lock_get_id);
448
449/**
450 * hwspin_lock_request() - request an hwspinlock
451 *
452 * This function should be called by users of the hwspinlock device,
453 * in order to dynamically assign them an unused hwspinlock.
454 * Usually the user of this lock will then have to communicate the lock's id
455 * to the remote core before it can be used for synchronization (to get the
456 * id of a given hwlock, use hwspin_lock_get_id()).
457 *
458 * Should be called from a process context (might sleep)
459 *
460 * Returns the address of the assigned hwspinlock, or NULL on error
461 */
462struct hwspinlock *hwspin_lock_request(void)
463{
464 struct hwspinlock *hwlock;
465 int ret;
466
467 mutex_lock(&hwspinlock_tree_lock);
468
469 /* look for an unused lock */
470 ret = radix_tree_gang_lookup_tag(&hwspinlock_tree, (void **)&hwlock,
471 0, 1, HWSPINLOCK_UNUSED);
472 if (ret == 0) {
473 pr_warn("a free hwspinlock is not available\n");
474 hwlock = NULL;
475 goto out;
476 }
477
478 /* sanity check that should never fail */
479 WARN_ON(ret > 1);
480
481 /* mark as used and power up */
482 ret = __hwspin_lock_request(hwlock);
483 if (ret < 0)
484 hwlock = NULL;
485
486out:
487 mutex_unlock(&hwspinlock_tree_lock);
488 return hwlock;
489}
490EXPORT_SYMBOL_GPL(hwspin_lock_request);
491
492/**
493 * hwspin_lock_request_specific() - request for a specific hwspinlock
494 * @id: index of the specific hwspinlock that is requested
495 *
496 * This function should be called by users of the hwspinlock module,
497 * in order to assign them a specific hwspinlock.
498 * Usually early board code will be calling this function in order to
499 * reserve specific hwspinlock ids for predefined purposes.
500 *
501 * Should be called from a process context (might sleep)
502 *
503 * Returns the address of the assigned hwspinlock, or NULL on error
504 */
505struct hwspinlock *hwspin_lock_request_specific(unsigned int id)
506{
507 struct hwspinlock *hwlock;
508 int ret;
509
510 mutex_lock(&hwspinlock_tree_lock);
511
512 /* make sure this hwspinlock exists */
513 hwlock = radix_tree_lookup(&hwspinlock_tree, id);
514 if (!hwlock) {
515 pr_warn("hwspinlock %u does not exist\n", id);
516 goto out;
517 }
518
519 /* sanity check (this shouldn't happen) */
520 WARN_ON(hwlock_to_id(hwlock) != id);
521
522 /* make sure this hwspinlock is unused */
523 ret = radix_tree_tag_get(&hwspinlock_tree, id, HWSPINLOCK_UNUSED);
524 if (ret == 0) {
525 pr_warn("hwspinlock %u is already in use\n", id);
526 hwlock = NULL;
527 goto out;
528 }
529
530 /* mark as used and power up */
531 ret = __hwspin_lock_request(hwlock);
532 if (ret < 0)
533 hwlock = NULL;
534
535out:
536 mutex_unlock(&hwspinlock_tree_lock);
537 return hwlock;
538}
539EXPORT_SYMBOL_GPL(hwspin_lock_request_specific);
540
541/**
542 * hwspin_lock_free() - free a specific hwspinlock
543 * @hwlock: the specific hwspinlock to free
544 *
545 * This function mark @hwlock as free again.
546 * Should only be called with an @hwlock that was retrieved from
547 * an earlier call to omap_hwspin_lock_request{_specific}.
548 *
549 * Should be called from a process context (might sleep)
550 *
551 * Returns 0 on success, or an appropriate error code on failure
552 */
553int hwspin_lock_free(struct hwspinlock *hwlock)
554{
555 struct device *dev = hwlock->bank->dev;
556 struct hwspinlock *tmp;
557 int ret;
558
559 if (!hwlock) {
560 pr_err("invalid hwlock\n");
561 return -EINVAL;
562 }
563
564 mutex_lock(&hwspinlock_tree_lock);
565
566 /* make sure the hwspinlock is used */
567 ret = radix_tree_tag_get(&hwspinlock_tree, hwlock_to_id(hwlock),
568 HWSPINLOCK_UNUSED);
569 if (ret == 1) {
570 dev_err(dev, "%s: hwlock is already free\n", __func__);
571 dump_stack();
572 ret = -EINVAL;
573 goto out;
574 }
575
576 /* notify the underlying device that power is not needed */
577 ret = pm_runtime_put(dev);
578 if (ret < 0)
579 goto out;
580
581 /* mark this hwspinlock as available */
582 tmp = radix_tree_tag_set(&hwspinlock_tree, hwlock_to_id(hwlock),
583 HWSPINLOCK_UNUSED);
584
585 /* sanity check (this shouldn't happen) */
586 WARN_ON(tmp != hwlock);
587
588 module_put(dev->driver->owner);
589
590out:
591 mutex_unlock(&hwspinlock_tree_lock);
592 return ret;
593}
594EXPORT_SYMBOL_GPL(hwspin_lock_free);
595
596MODULE_LICENSE("GPL v2");
597MODULE_DESCRIPTION("Hardware spinlock interface");
598MODULE_AUTHOR("Ohad Ben-Cohen <ohad@wizery.com>");