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2024-02-20 ea08eeccae9297f7aabd2ef7f0c2517ac4549acc 
 kernel/drivers/reset/core.c
....@@ -1,12 +1,8 @@
1
+// SPDX-License-Identifier: GPL-2.0-or-later
12 /*
23  * Reset Controller framework
34  *
45  * Copyright 2013 Philipp Zabel, Pengutronix
5
- *
6
- * This program is free software; you can redistribute it and/or modify
7
- * it under the terms of the GNU General Public License as published by
8
- * the Free Software Foundation; either version 2 of the License, or
9
- * (at your option) any later version.
106  */
117 #include <linux/atomic.h>
128 #include <linux/device.h>
....@@ -34,8 +30,10 @@
3430  * @id: ID of the reset controller in the reset
3531  *      controller device
3632  * @refcnt: Number of gets of this reset_control
33
+ * @acquired: Only one reset_control may be acquired for a given rcdev and id.
3734  * @shared: Is this a shared (1), or an exclusive (0) reset_control?
38
- * @deassert_cnt: Number of times this reset line has been deasserted
35
+ * @array: Is this an array of reset controls (1)?
36
+ * @deassert_count: Number of times this reset line has been deasserted
3937  * @triggered_count: Number of times this reset line has been reset. Currently
4038  *                   only used for shared resets, which means that the value
4139  *                   will be either 0 or 1.
....@@ -45,6 +43,7 @@
4543 	struct list_head list;
4644 	unsigned int id;
4745 	struct kref refcnt;
46
+	bool acquired;
4847 	bool shared;
4948 	bool array;
5049 	atomic_t deassert_count;
....@@ -63,14 +62,26 @@
6362 	struct reset_control *rstc[];
6463 };
6564 
65
+static const char *rcdev_name(struct reset_controller_dev *rcdev)
66
+{
67
+	if (rcdev->dev)
68
+		return dev_name(rcdev->dev);
69
+
70
+	if (rcdev->of_node)
71
+		return rcdev->of_node->full_name;
72
+
73
+	return NULL;
74
+}
75
+
6676 /**
6777  * of_reset_simple_xlate - translate reset_spec to the reset line number
6878  * @rcdev: a pointer to the reset controller device
6979  * @reset_spec: reset line specifier as found in the device tree
70
- * @flags: a flags pointer to fill in (optional)
7180  *
72
- * This simple translation function should be used for reset controllers
73
- * with 1:1 mapping, where reset lines can be indexed by number without gaps.
81
+ * This static translation function is used by default if of_xlate in
82
+ * :c:type:`reset_controller_dev` is not set. It is useful for all reset
83
+ * controllers with 1:1 mapping, where reset lines can be indexed by number
84
+ * without gaps.
7485  */
7586 static int of_reset_simple_xlate(struct reset_controller_dev *rcdev,
7687 			  const struct of_phandle_args *reset_spec)
....@@ -140,12 +151,13 @@
140151 		return -ENOMEM;
141152 
142153 	ret = reset_controller_register(rcdev);
143
-	if (!ret) {
144
-		*rcdevp = rcdev;
145
-		devres_add(dev, rcdevp);
146
-	} else {
154
+	if (ret) {
147155 		devres_free(rcdevp);
156
+		return ret;
148157 	}
158
+
159
+	*rcdevp = rcdev;
160
+	devres_add(dev, rcdevp);
149161 
150162 	return ret;
151163 }
....@@ -232,6 +244,34 @@
232244 	return ret;
233245 }
234246 
247
+static int reset_control_array_acquire(struct reset_control_array *resets)
248
+{
249
+	unsigned int i;
250
+	int err;
251
+
252
+	for (i = 0; i < resets->num_rstcs; i++) {
253
+		err = reset_control_acquire(resets->rstc[i]);
254
+		if (err < 0)
255
+			goto release;
256
+	}
257
+
258
+	return 0;
259
+
260
+release:
261
+	while (i--)
262
+		reset_control_release(resets->rstc[i]);
263
+
264
+	return err;
265
+}
266
+
267
+static void reset_control_array_release(struct reset_control_array *resets)
268
+{
269
+	unsigned int i;
270
+
271
+	for (i = 0; i < resets->num_rstcs; i++)
272
+		reset_control_release(resets->rstc[i]);
273
+}
274
+
235275 static inline bool reset_control_is_array(struct reset_control *rstc)
236276 {
237277 	return rstc->array;
....@@ -272,6 +312,9 @@
272312 
273313 		if (atomic_inc_return(&rstc->triggered_count) != 1)
274314 			return 0;
315
+	} else {
316
+		if (!rstc->acquired)
317
+			return -EPERM;
275318 	}
276319 
277320 	ret = rstc->rcdev->ops->reset(rstc->rcdev, rstc->id);
....@@ -294,7 +337,6 @@
294337  * internal state to be reset, but must be prepared for this to happen.
295338  * Consumers must not use reset_control_reset on shared reset lines when
296339  * reset_control_(de)assert has been used.
297
- * return 0.
298340  *
299341  * If rstc is NULL it is an optional reset and the function will just
300342  * return 0.
....@@ -334,6 +376,12 @@
334376 		 */
335377 		if (!rstc->rcdev->ops->assert)
336378 			return -ENOTSUPP;
379
+
380
+		if (!rstc->acquired) {
381
+			WARN(1, "reset %s (ID: %u) is not acquired\n",
382
+			     rcdev_name(rstc->rcdev), rstc->id);
383
+			return -EPERM;
384
+		}
337385 	}
338386 
339387 	return rstc->rcdev->ops->assert(rstc->rcdev, rstc->id);
....@@ -347,7 +395,6 @@
347395  * After calling this function, the reset is guaranteed to be deasserted.
348396  * Consumers must not use reset_control_reset on shared reset lines when
349397  * reset_control_(de)assert has been used.
350
- * return 0.
351398  *
352399  * If rstc is NULL it is an optional reset and the function will just
353400  * return 0.
....@@ -369,6 +416,12 @@
369416 
370417 		if (atomic_inc_return(&rstc->deassert_count) != 1)
371418 			return 0;
419
+	} else {
420
+		if (!rstc->acquired) {
421
+			WARN(1, "reset %s (ID: %u) is not acquired\n",
422
+			     rcdev_name(rstc->rcdev), rstc->id);
423
+			return -EPERM;
424
+		}
372425 	}
373426 
374427 	/*
....@@ -406,9 +459,87 @@
406459 }
407460 EXPORT_SYMBOL_GPL(reset_control_status);
408461 
462
+/**
463
+ * reset_control_acquire() - acquires a reset control for exclusive use
464
+ * @rstc: reset control
465
+ *
466
+ * This is used to explicitly acquire a reset control for exclusive use. Note
467
+ * that exclusive resets are requested as acquired by default. In order for a
468
+ * second consumer to be able to control the reset, the first consumer has to
469
+ * release it first. Typically the easiest way to achieve this is to call the
470
+ * reset_control_get_exclusive_released() to obtain an instance of the reset
471
+ * control. Such reset controls are not acquired by default.
472
+ *
473
+ * Consumers implementing shared access to an exclusive reset need to follow
474
+ * a specific protocol in order to work together. Before consumers can change
475
+ * a reset they must acquire exclusive access using reset_control_acquire().
476
+ * After they are done operating the reset, they must release exclusive access
477
+ * with a call to reset_control_release(). Consumers are not granted exclusive
478
+ * access to the reset as long as another consumer hasn't released a reset.
479
+ *
480
+ * See also: reset_control_release()
481
+ */
482
+int reset_control_acquire(struct reset_control *rstc)
483
+{
484
+	struct reset_control *rc;
485
+
486
+	if (!rstc)
487
+		return 0;
488
+
489
+	if (WARN_ON(IS_ERR(rstc)))
490
+		return -EINVAL;
491
+
492
+	if (reset_control_is_array(rstc))
493
+		return reset_control_array_acquire(rstc_to_array(rstc));
494
+
495
+	mutex_lock(&reset_list_mutex);
496
+
497
+	if (rstc->acquired) {
498
+		mutex_unlock(&reset_list_mutex);
499
+		return 0;
500
+	}
501
+
502
+	list_for_each_entry(rc, &rstc->rcdev->reset_control_head, list) {
503
+		if (rstc != rc && rstc->id == rc->id) {
504
+			if (rc->acquired) {
505
+				mutex_unlock(&reset_list_mutex);
506
+				return -EBUSY;
507
+			}
508
+		}
509
+	}
510
+
511
+	rstc->acquired = true;
512
+
513
+	mutex_unlock(&reset_list_mutex);
514
+	return 0;
515
+}
516
+EXPORT_SYMBOL_GPL(reset_control_acquire);
517
+
518
+/**
519
+ * reset_control_release() - releases exclusive access to a reset control
520
+ * @rstc: reset control
521
+ *
522
+ * Releases exclusive access right to a reset control previously obtained by a
523
+ * call to reset_control_acquire(). Until a consumer calls this function, no
524
+ * other consumers will be granted exclusive access.
525
+ *
526
+ * See also: reset_control_acquire()
527
+ */
528
+void reset_control_release(struct reset_control *rstc)
529
+{
530
+	if (!rstc || WARN_ON(IS_ERR(rstc)))
531
+		return;
532
+
533
+	if (reset_control_is_array(rstc))
534
+		reset_control_array_release(rstc_to_array(rstc));
535
+	else
536
+		rstc->acquired = false;
537
+}
538
+EXPORT_SYMBOL_GPL(reset_control_release);
539
+
409540 static struct reset_control *__reset_control_get_internal(
410541 				struct reset_controller_dev *rcdev,
411
-				unsigned int index, bool shared)
542
+				unsigned int index, bool shared, bool acquired)
412543 {
413544 	struct reset_control *rstc;
414545 
....@@ -416,6 +547,14 @@
416547 
417548 	list_for_each_entry(rstc, &rcdev->reset_control_head, list) {
418549 		if (rstc->id == index) {
550
+			/*
551
+			 * Allow creating a secondary exclusive reset_control
552
+			 * that is initially not acquired for an already
553
+			 * controlled reset line.
554
+			 */
555
+			if (!rstc->shared && !shared && !acquired)
556
+				break;
557
+
419558 			if (WARN_ON(!rstc->shared || !shared))
420559 				return ERR_PTR(-EBUSY);
421560 
....@@ -437,6 +576,7 @@
437576 	list_add(&rstc->list, &rcdev->reset_control_head);
438577 	rstc->id = index;
439578 	kref_init(&rstc->refcnt);
579
+	rstc->acquired = acquired;
440580 	rstc->shared = shared;
441581 
442582 	return rstc;
....@@ -464,7 +604,7 @@
464604 
465605 struct reset_control *__of_reset_control_get(struct device_node *node,
466606 				     const char *id, int index, bool shared,
467
-				     bool optional)
607
+				     bool optional, bool acquired)
468608 {
469609 	struct reset_control *rstc;
470610 	struct reset_controller_dev *r, *rcdev;
....@@ -517,7 +657,7 @@
517657 	}
518658 
519659 	/* reset_list_mutex also protects the rcdev's reset_control list */
520
-	rstc = __reset_control_get_internal(rcdev, rstc_id, shared);
660
+	rstc = __reset_control_get_internal(rcdev, rstc_id, shared, acquired);
521661 
522662 out:
523663 	mutex_unlock(&reset_list_mutex);
....@@ -547,15 +687,12 @@
547687 
548688 static struct reset_control *
549689 __reset_control_get_from_lookup(struct device *dev, const char *con_id,
550
-				bool shared, bool optional)
690
+				bool shared, bool optional, bool acquired)
551691 {
552692 	const struct reset_control_lookup *lookup;
553693 	struct reset_controller_dev *rcdev;
554694 	const char *dev_id = dev_name(dev);
555695 	struct reset_control *rstc = NULL;
556
-
557
-	if (!dev)
558
-		return ERR_PTR(-EINVAL);
559696 
560697 	mutex_lock(&reset_lookup_mutex);
561698 
....@@ -577,7 +714,7 @@
577714 
578715 			rstc = __reset_control_get_internal(rcdev,
579716 							    lookup->index,
580
-							    shared);
717
+							    shared, acquired);
581718 			mutex_unlock(&reset_list_mutex);
582719 			break;
583720 		}
....@@ -592,13 +729,18 @@
592729 }
593730 
594731 struct reset_control *__reset_control_get(struct device *dev, const char *id,
595
-					  int index, bool shared, bool optional)
732
+					  int index, bool shared, bool optional,
733
+					  bool acquired)
596734 {
735
+	if (WARN_ON(shared && acquired))
736
+		return ERR_PTR(-EINVAL);
737
+
597738 	if (dev->of_node)
598739 		return __of_reset_control_get(dev->of_node, id, index, shared,
599
-					      optional);
740
+					      optional, acquired);
600741 
601
-	return __reset_control_get_from_lookup(dev, id, shared, optional);
742
+	return __reset_control_get_from_lookup(dev, id, shared, optional,
743
+					       acquired);
602744 }
603745 EXPORT_SYMBOL_GPL(__reset_control_get);
604746 
....@@ -640,7 +782,7 @@
640782 
641783 struct reset_control *__devm_reset_control_get(struct device *dev,
642784 				     const char *id, int index, bool shared,
643
-				     bool optional)
785
+				     bool optional, bool acquired)
644786 {
645787 	struct reset_control **ptr, *rstc;
646788 
....@@ -649,13 +791,14 @@
649791 	if (!ptr)
650792 		return ERR_PTR(-ENOMEM);
651793 
652
-	rstc = __reset_control_get(dev, id, index, shared, optional);
653
-	if (!IS_ERR(rstc)) {
654
-		*ptr = rstc;
655
-		devres_add(dev, ptr);
656
-	} else {
794
+	rstc = __reset_control_get(dev, id, index, shared, optional, acquired);
795
+	if (IS_ERR_OR_NULL(rstc)) {
657796 		devres_free(ptr);
797
+		return rstc;
658798 	}
799
+
800
+	*ptr = rstc;
801
+	devres_add(dev, ptr);
659802 
660803 	return rstc;
661804 }
....@@ -676,7 +819,7 @@
676819 	struct reset_control *rstc;
677820 	int ret;
678821 
679
-	rstc = __reset_control_get(dev, NULL, 0, 0, optional);
822
+	rstc = __reset_control_get(dev, NULL, 0, 0, optional, true);
680823 	if (IS_ERR(rstc))
681824 		return PTR_ERR(rstc);
682825 
....@@ -688,9 +831,10 @@
688831 }
689832 EXPORT_SYMBOL_GPL(__device_reset);
690833 
691
-/**
834
+/*
692835  * APIs to manage an array of reset controls.
693836  */
837
+
694838 /**
695839  * of_reset_control_get_count - Count number of resets available with a device
696840  *
....@@ -720,12 +864,14 @@
720864  * @np: device node for the device that requests the reset controls array
721865  * @shared: whether reset controls are shared or not
722866  * @optional: whether it is optional to get the reset controls
867
+ * @acquired: only one reset control may be acquired for a given controller
868
+ *            and ID
723869  *
724
- * Returns pointer to allocated reset_control_array on success or
725
- * error on failure
870
+ * Returns pointer to allocated reset_control on success or error on failure
726871  */
727872 struct reset_control *
728
-of_reset_control_array_get(struct device_node *np, bool shared, bool optional)
873
+of_reset_control_array_get(struct device_node *np, bool shared, bool optional,
874
+			   bool acquired)
729875 {
730876 	struct reset_control_array *resets;
731877 	struct reset_control *rstc;
....@@ -740,7 +886,8 @@
740886 		return ERR_PTR(-ENOMEM);
741887 
742888 	for (i = 0; i < num; i++) {
743
-		rstc = __of_reset_control_get(np, NULL, i, shared, optional);
889
+		rstc = __of_reset_control_get(np, NULL, i, shared, optional,
890
+					      acquired);
744891 		if (IS_ERR(rstc))
745892 			goto err_rst;
746893 		resets->rstc[i] = rstc;
....@@ -773,29 +920,69 @@
773920  * that just have to be asserted or deasserted, without any
774921  * requirements on the order.
775922  *
776
- * Returns pointer to allocated reset_control_array on success or
777
- * error on failure
923
+ * Returns pointer to allocated reset_control on success or error on failure
778924  */
779925 struct reset_control *
780926 devm_reset_control_array_get(struct device *dev, bool shared, bool optional)
781927 {
782
-	struct reset_control **devres;
783
-	struct reset_control *rstc;
928
+	struct reset_control **ptr, *rstc;
784929 
785
-	devres = devres_alloc(devm_reset_control_release, sizeof(*devres),
786
-			      GFP_KERNEL);
787
-	if (!devres)
930
+	ptr = devres_alloc(devm_reset_control_release, sizeof(*ptr),
931
+			   GFP_KERNEL);
932
+	if (!ptr)
788933 		return ERR_PTR(-ENOMEM);
789934 
790
-	rstc = of_reset_control_array_get(dev->of_node, shared, optional);
791
-	if (IS_ERR(rstc)) {
792
-		devres_free(devres);
935
+	rstc = of_reset_control_array_get(dev->of_node, shared, optional, true);
936
+	if (IS_ERR_OR_NULL(rstc)) {
937
+		devres_free(ptr);
793938 		return rstc;
794939 	}
795940 
796
-	*devres = rstc;
797
-	devres_add(dev, devres);
941
+	*ptr = rstc;
942
+	devres_add(dev, ptr);
798943 
799944 	return rstc;
800945 }
801946 EXPORT_SYMBOL_GPL(devm_reset_control_array_get);
947
+
948
+static int reset_control_get_count_from_lookup(struct device *dev)
949
+{
950
+	const struct reset_control_lookup *lookup;
951
+	const char *dev_id;
952
+	int count = 0;
953
+
954
+	if (!dev)
955
+		return -EINVAL;
956
+
957
+	dev_id = dev_name(dev);
958
+	mutex_lock(&reset_lookup_mutex);
959
+
960
+	list_for_each_entry(lookup, &reset_lookup_list, list) {
961
+		if (!strcmp(lookup->dev_id, dev_id))
962
+			count++;
963
+	}
964
+
965
+	mutex_unlock(&reset_lookup_mutex);
966
+
967
+	if (count == 0)
968
+		count = -ENOENT;
969
+
970
+	return count;
971
+}
972
+
973
+/**
974
+ * reset_control_get_count - Count number of resets available with a device
975
+ *
976
+ * @dev: device for which to return the number of resets
977
+ *
978
+ * Returns positive reset count on success, or error number on failure and
979
+ * on count being zero.
980
+ */
981
+int reset_control_get_count(struct device *dev)
982
+{
983
+	if (dev->of_node)
984
+		return of_reset_control_get_count(dev->of_node);
985
+
986
+	return reset_control_get_count_from_lookup(dev);
987
+}
988
+EXPORT_SYMBOL_GPL(reset_control_get_count);