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  */
50 static 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  */
57 static 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  */
91 int __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 }
169 EXPORT_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  */
206 int __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 }
244 EXPORT_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  */
265 void __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 }
303 EXPORT_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  */
316 static inline int
317 of_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  */
339 int 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 
386 out:
387 	of_node_put(args.np);
388 	return ret ? ret : id;
389 }
390 EXPORT_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  */
406 int 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 }
419 EXPORT_SYMBOL_GPL(of_hwspin_lock_get_id_byname);
420 
421 static 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 
441 out:
442 	mutex_unlock(&hwspinlock_tree_lock);
443 	return 0;
444 }
445 
446 static 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 
466 out:
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  */
486 int 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 
516 reg_failed:
517 	while (--i >= 0)
518 		hwspin_lock_unregister_single(base_id + i);
519 	return ret;
520 }
521 EXPORT_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  */
534 int 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 }
552 EXPORT_SYMBOL_GPL(hwspin_lock_unregister);
553 
554 static void devm_hwspin_lock_unreg(struct device *dev, void *res)
555 {
556 	hwspin_lock_unregister(*(struct hwspinlock_device **)res);
557 }
558 
559 static 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  */
583 int 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 }
594 EXPORT_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  */
612 int 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 }
634 EXPORT_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  */
646 static 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  */
685 int 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 }
694 EXPORT_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  */
709 struct 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 
733 out:
734 	mutex_unlock(&hwspinlock_tree_lock);
735 	return hwlock;
736 }
737 EXPORT_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  */
752 struct 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 
782 out:
783 	mutex_unlock(&hwspinlock_tree_lock);
784 	return hwlock;
785 }
786 EXPORT_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  */
800 int 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 
836 out:
837 	mutex_unlock(&hwspinlock_tree_lock);
838 	return ret;
839 }
840 EXPORT_SYMBOL_GPL(hwspin_lock_free);
841 
842 static 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 
852 static 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  */
870 int 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 }
880 EXPORT_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  */
896 struct 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 }
914 EXPORT_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  */
931 struct 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 }
950 EXPORT_SYMBOL_GPL(devm_hwspin_lock_request_specific);
951 
952 MODULE_LICENSE("GPL v2");
953 MODULE_DESCRIPTION("Hardware spinlock interface");
954 MODULE_AUTHOR("Ohad Ben-Cohen <ohad@wizery.com>");
955