xref: /linux/drivers/interconnect/core.c (revision f86fd32d)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Interconnect framework core driver
4  *
5  * Copyright (c) 2017-2019, Linaro Ltd.
6  * Author: Georgi Djakov <georgi.djakov@linaro.org>
7  */
8 
9 #include <linux/debugfs.h>
10 #include <linux/device.h>
11 #include <linux/idr.h>
12 #include <linux/init.h>
13 #include <linux/interconnect.h>
14 #include <linux/interconnect-provider.h>
15 #include <linux/list.h>
16 #include <linux/module.h>
17 #include <linux/mutex.h>
18 #include <linux/slab.h>
19 #include <linux/of.h>
20 #include <linux/overflow.h>
21 
22 #include "internal.h"
23 
24 #define CREATE_TRACE_POINTS
25 #include "trace.h"
26 
27 static DEFINE_IDR(icc_idr);
28 static LIST_HEAD(icc_providers);
29 static DEFINE_MUTEX(icc_lock);
30 static struct dentry *icc_debugfs_dir;
31 
32 static void icc_summary_show_one(struct seq_file *s, struct icc_node *n)
33 {
34 	if (!n)
35 		return;
36 
37 	seq_printf(s, "%-42s %12u %12u\n",
38 		   n->name, n->avg_bw, n->peak_bw);
39 }
40 
41 static int icc_summary_show(struct seq_file *s, void *data)
42 {
43 	struct icc_provider *provider;
44 
45 	seq_puts(s, " node                                  tag          avg         peak\n");
46 	seq_puts(s, "--------------------------------------------------------------------\n");
47 
48 	mutex_lock(&icc_lock);
49 
50 	list_for_each_entry(provider, &icc_providers, provider_list) {
51 		struct icc_node *n;
52 
53 		list_for_each_entry(n, &provider->nodes, node_list) {
54 			struct icc_req *r;
55 
56 			icc_summary_show_one(s, n);
57 			hlist_for_each_entry(r, &n->req_list, req_node) {
58 				if (!r->dev)
59 					continue;
60 
61 				seq_printf(s, "  %-27s %12u %12u %12u\n",
62 					   dev_name(r->dev), r->tag, r->avg_bw,
63 					   r->peak_bw);
64 			}
65 		}
66 	}
67 
68 	mutex_unlock(&icc_lock);
69 
70 	return 0;
71 }
72 DEFINE_SHOW_ATTRIBUTE(icc_summary);
73 
74 static void icc_graph_show_link(struct seq_file *s, int level,
75 				struct icc_node *n, struct icc_node *m)
76 {
77 	seq_printf(s, "%s\"%d:%s\" -> \"%d:%s\"\n",
78 		   level == 2 ? "\t\t" : "\t",
79 		   n->id, n->name, m->id, m->name);
80 }
81 
82 static void icc_graph_show_node(struct seq_file *s, struct icc_node *n)
83 {
84 	seq_printf(s, "\t\t\"%d:%s\" [label=\"%d:%s",
85 		   n->id, n->name, n->id, n->name);
86 	seq_printf(s, "\n\t\t\t|avg_bw=%ukBps", n->avg_bw);
87 	seq_printf(s, "\n\t\t\t|peak_bw=%ukBps", n->peak_bw);
88 	seq_puts(s, "\"]\n");
89 }
90 
91 static int icc_graph_show(struct seq_file *s, void *data)
92 {
93 	struct icc_provider *provider;
94 	struct icc_node *n;
95 	int cluster_index = 0;
96 	int i;
97 
98 	seq_puts(s, "digraph {\n\trankdir = LR\n\tnode [shape = record]\n");
99 	mutex_lock(&icc_lock);
100 
101 	/* draw providers as cluster subgraphs */
102 	cluster_index = 0;
103 	list_for_each_entry(provider, &icc_providers, provider_list) {
104 		seq_printf(s, "\tsubgraph cluster_%d {\n", ++cluster_index);
105 		if (provider->dev)
106 			seq_printf(s, "\t\tlabel = \"%s\"\n",
107 				   dev_name(provider->dev));
108 
109 		/* draw nodes */
110 		list_for_each_entry(n, &provider->nodes, node_list)
111 			icc_graph_show_node(s, n);
112 
113 		/* draw internal links */
114 		list_for_each_entry(n, &provider->nodes, node_list)
115 			for (i = 0; i < n->num_links; ++i)
116 				if (n->provider == n->links[i]->provider)
117 					icc_graph_show_link(s, 2, n,
118 							    n->links[i]);
119 
120 		seq_puts(s, "\t}\n");
121 	}
122 
123 	/* draw external links */
124 	list_for_each_entry(provider, &icc_providers, provider_list)
125 		list_for_each_entry(n, &provider->nodes, node_list)
126 			for (i = 0; i < n->num_links; ++i)
127 				if (n->provider != n->links[i]->provider)
128 					icc_graph_show_link(s, 1, n,
129 							    n->links[i]);
130 
131 	mutex_unlock(&icc_lock);
132 	seq_puts(s, "}");
133 
134 	return 0;
135 }
136 DEFINE_SHOW_ATTRIBUTE(icc_graph);
137 
138 static struct icc_node *node_find(const int id)
139 {
140 	return idr_find(&icc_idr, id);
141 }
142 
143 static struct icc_path *path_init(struct device *dev, struct icc_node *dst,
144 				  ssize_t num_nodes)
145 {
146 	struct icc_node *node = dst;
147 	struct icc_path *path;
148 	int i;
149 
150 	path = kzalloc(struct_size(path, reqs, num_nodes), GFP_KERNEL);
151 	if (!path)
152 		return ERR_PTR(-ENOMEM);
153 
154 	path->num_nodes = num_nodes;
155 
156 	for (i = num_nodes - 1; i >= 0; i--) {
157 		node->provider->users++;
158 		hlist_add_head(&path->reqs[i].req_node, &node->req_list);
159 		path->reqs[i].node = node;
160 		path->reqs[i].dev = dev;
161 		/* reference to previous node was saved during path traversal */
162 		node = node->reverse;
163 	}
164 
165 	return path;
166 }
167 
168 static struct icc_path *path_find(struct device *dev, struct icc_node *src,
169 				  struct icc_node *dst)
170 {
171 	struct icc_path *path = ERR_PTR(-EPROBE_DEFER);
172 	struct icc_node *n, *node = NULL;
173 	struct list_head traverse_list;
174 	struct list_head edge_list;
175 	struct list_head visited_list;
176 	size_t i, depth = 1;
177 	bool found = false;
178 
179 	INIT_LIST_HEAD(&traverse_list);
180 	INIT_LIST_HEAD(&edge_list);
181 	INIT_LIST_HEAD(&visited_list);
182 
183 	list_add(&src->search_list, &traverse_list);
184 	src->reverse = NULL;
185 
186 	do {
187 		list_for_each_entry_safe(node, n, &traverse_list, search_list) {
188 			if (node == dst) {
189 				found = true;
190 				list_splice_init(&edge_list, &visited_list);
191 				list_splice_init(&traverse_list, &visited_list);
192 				break;
193 			}
194 			for (i = 0; i < node->num_links; i++) {
195 				struct icc_node *tmp = node->links[i];
196 
197 				if (!tmp) {
198 					path = ERR_PTR(-ENOENT);
199 					goto out;
200 				}
201 
202 				if (tmp->is_traversed)
203 					continue;
204 
205 				tmp->is_traversed = true;
206 				tmp->reverse = node;
207 				list_add_tail(&tmp->search_list, &edge_list);
208 			}
209 		}
210 
211 		if (found)
212 			break;
213 
214 		list_splice_init(&traverse_list, &visited_list);
215 		list_splice_init(&edge_list, &traverse_list);
216 
217 		/* count the hops including the source */
218 		depth++;
219 
220 	} while (!list_empty(&traverse_list));
221 
222 out:
223 
224 	/* reset the traversed state */
225 	list_for_each_entry_reverse(n, &visited_list, search_list)
226 		n->is_traversed = false;
227 
228 	if (found)
229 		path = path_init(dev, dst, depth);
230 
231 	return path;
232 }
233 
234 /*
235  * We want the path to honor all bandwidth requests, so the average and peak
236  * bandwidth requirements from each consumer are aggregated at each node.
237  * The aggregation is platform specific, so each platform can customize it by
238  * implementing its own aggregate() function.
239  */
240 
241 static int aggregate_requests(struct icc_node *node)
242 {
243 	struct icc_provider *p = node->provider;
244 	struct icc_req *r;
245 
246 	node->avg_bw = 0;
247 	node->peak_bw = 0;
248 
249 	if (p->pre_aggregate)
250 		p->pre_aggregate(node);
251 
252 	hlist_for_each_entry(r, &node->req_list, req_node)
253 		p->aggregate(node, r->tag, r->avg_bw, r->peak_bw,
254 			     &node->avg_bw, &node->peak_bw);
255 
256 	return 0;
257 }
258 
259 static int apply_constraints(struct icc_path *path)
260 {
261 	struct icc_node *next, *prev = NULL;
262 	int ret = -EINVAL;
263 	int i;
264 
265 	for (i = 0; i < path->num_nodes; i++) {
266 		next = path->reqs[i].node;
267 
268 		/*
269 		 * Both endpoints should be valid master-slave pairs of the
270 		 * same interconnect provider that will be configured.
271 		 */
272 		if (!prev || next->provider != prev->provider) {
273 			prev = next;
274 			continue;
275 		}
276 
277 		/* set the constraints */
278 		ret = next->provider->set(prev, next);
279 		if (ret)
280 			goto out;
281 
282 		prev = next;
283 	}
284 out:
285 	return ret;
286 }
287 
288 int icc_std_aggregate(struct icc_node *node, u32 tag, u32 avg_bw,
289 		      u32 peak_bw, u32 *agg_avg, u32 *agg_peak)
290 {
291 	*agg_avg += avg_bw;
292 	*agg_peak = max(*agg_peak, peak_bw);
293 
294 	return 0;
295 }
296 EXPORT_SYMBOL_GPL(icc_std_aggregate);
297 
298 /* of_icc_xlate_onecell() - Translate function using a single index.
299  * @spec: OF phandle args to map into an interconnect node.
300  * @data: private data (pointer to struct icc_onecell_data)
301  *
302  * This is a generic translate function that can be used to model simple
303  * interconnect providers that have one device tree node and provide
304  * multiple interconnect nodes. A single cell is used as an index into
305  * an array of icc nodes specified in the icc_onecell_data struct when
306  * registering the provider.
307  */
308 struct icc_node *of_icc_xlate_onecell(struct of_phandle_args *spec,
309 				      void *data)
310 {
311 	struct icc_onecell_data *icc_data = data;
312 	unsigned int idx = spec->args[0];
313 
314 	if (idx >= icc_data->num_nodes) {
315 		pr_err("%s: invalid index %u\n", __func__, idx);
316 		return ERR_PTR(-EINVAL);
317 	}
318 
319 	return icc_data->nodes[idx];
320 }
321 EXPORT_SYMBOL_GPL(of_icc_xlate_onecell);
322 
323 /**
324  * of_icc_get_from_provider() - Look-up interconnect node
325  * @spec: OF phandle args to use for look-up
326  *
327  * Looks for interconnect provider under the node specified by @spec and if
328  * found, uses xlate function of the provider to map phandle args to node.
329  *
330  * Returns a valid pointer to struct icc_node on success or ERR_PTR()
331  * on failure.
332  */
333 static struct icc_node *of_icc_get_from_provider(struct of_phandle_args *spec)
334 {
335 	struct icc_node *node = ERR_PTR(-EPROBE_DEFER);
336 	struct icc_provider *provider;
337 
338 	if (!spec || spec->args_count != 1)
339 		return ERR_PTR(-EINVAL);
340 
341 	mutex_lock(&icc_lock);
342 	list_for_each_entry(provider, &icc_providers, provider_list) {
343 		if (provider->dev->of_node == spec->np)
344 			node = provider->xlate(spec, provider->data);
345 		if (!IS_ERR(node))
346 			break;
347 	}
348 	mutex_unlock(&icc_lock);
349 
350 	return node;
351 }
352 
353 /**
354  * of_icc_get() - get a path handle from a DT node based on name
355  * @dev: device pointer for the consumer device
356  * @name: interconnect path name
357  *
358  * This function will search for a path between two endpoints and return an
359  * icc_path handle on success. Use icc_put() to release constraints when they
360  * are not needed anymore.
361  * If the interconnect API is disabled, NULL is returned and the consumer
362  * drivers will still build. Drivers are free to handle this specifically,
363  * but they don't have to.
364  *
365  * Return: icc_path pointer on success or ERR_PTR() on error. NULL is returned
366  * when the API is disabled or the "interconnects" DT property is missing.
367  */
368 struct icc_path *of_icc_get(struct device *dev, const char *name)
369 {
370 	struct icc_path *path = ERR_PTR(-EPROBE_DEFER);
371 	struct icc_node *src_node, *dst_node;
372 	struct device_node *np = NULL;
373 	struct of_phandle_args src_args, dst_args;
374 	int idx = 0;
375 	int ret;
376 
377 	if (!dev || !dev->of_node)
378 		return ERR_PTR(-ENODEV);
379 
380 	np = dev->of_node;
381 
382 	/*
383 	 * When the consumer DT node do not have "interconnects" property
384 	 * return a NULL path to skip setting constraints.
385 	 */
386 	if (!of_find_property(np, "interconnects", NULL))
387 		return NULL;
388 
389 	/*
390 	 * We use a combination of phandle and specifier for endpoint. For now
391 	 * lets support only global ids and extend this in the future if needed
392 	 * without breaking DT compatibility.
393 	 */
394 	if (name) {
395 		idx = of_property_match_string(np, "interconnect-names", name);
396 		if (idx < 0)
397 			return ERR_PTR(idx);
398 	}
399 
400 	ret = of_parse_phandle_with_args(np, "interconnects",
401 					 "#interconnect-cells", idx * 2,
402 					 &src_args);
403 	if (ret)
404 		return ERR_PTR(ret);
405 
406 	of_node_put(src_args.np);
407 
408 	ret = of_parse_phandle_with_args(np, "interconnects",
409 					 "#interconnect-cells", idx * 2 + 1,
410 					 &dst_args);
411 	if (ret)
412 		return ERR_PTR(ret);
413 
414 	of_node_put(dst_args.np);
415 
416 	src_node = of_icc_get_from_provider(&src_args);
417 
418 	if (IS_ERR(src_node)) {
419 		if (PTR_ERR(src_node) != -EPROBE_DEFER)
420 			dev_err(dev, "error finding src node: %ld\n",
421 				PTR_ERR(src_node));
422 		return ERR_CAST(src_node);
423 	}
424 
425 	dst_node = of_icc_get_from_provider(&dst_args);
426 
427 	if (IS_ERR(dst_node)) {
428 		if (PTR_ERR(dst_node) != -EPROBE_DEFER)
429 			dev_err(dev, "error finding dst node: %ld\n",
430 				PTR_ERR(dst_node));
431 		return ERR_CAST(dst_node);
432 	}
433 
434 	mutex_lock(&icc_lock);
435 	path = path_find(dev, src_node, dst_node);
436 	mutex_unlock(&icc_lock);
437 	if (IS_ERR(path)) {
438 		dev_err(dev, "%s: invalid path=%ld\n", __func__, PTR_ERR(path));
439 		return path;
440 	}
441 
442 	if (name)
443 		path->name = kstrdup_const(name, GFP_KERNEL);
444 	else
445 		path->name = kasprintf(GFP_KERNEL, "%s-%s",
446 				       src_node->name, dst_node->name);
447 
448 	return path;
449 }
450 EXPORT_SYMBOL_GPL(of_icc_get);
451 
452 /**
453  * icc_set_tag() - set an optional tag on a path
454  * @path: the path we want to tag
455  * @tag: the tag value
456  *
457  * This function allows consumers to append a tag to the requests associated
458  * with a path, so that a different aggregation could be done based on this tag.
459  */
460 void icc_set_tag(struct icc_path *path, u32 tag)
461 {
462 	int i;
463 
464 	if (!path)
465 		return;
466 
467 	mutex_lock(&icc_lock);
468 
469 	for (i = 0; i < path->num_nodes; i++)
470 		path->reqs[i].tag = tag;
471 
472 	mutex_unlock(&icc_lock);
473 }
474 EXPORT_SYMBOL_GPL(icc_set_tag);
475 
476 /**
477  * icc_set_bw() - set bandwidth constraints on an interconnect path
478  * @path: reference to the path returned by icc_get()
479  * @avg_bw: average bandwidth in kilobytes per second
480  * @peak_bw: peak bandwidth in kilobytes per second
481  *
482  * This function is used by an interconnect consumer to express its own needs
483  * in terms of bandwidth for a previously requested path between two endpoints.
484  * The requests are aggregated and each node is updated accordingly. The entire
485  * path is locked by a mutex to ensure that the set() is completed.
486  * The @path can be NULL when the "interconnects" DT properties is missing,
487  * which will mean that no constraints will be set.
488  *
489  * Returns 0 on success, or an appropriate error code otherwise.
490  */
491 int icc_set_bw(struct icc_path *path, u32 avg_bw, u32 peak_bw)
492 {
493 	struct icc_node *node;
494 	u32 old_avg, old_peak;
495 	size_t i;
496 	int ret;
497 
498 	if (!path)
499 		return 0;
500 
501 	if (WARN_ON(IS_ERR(path) || !path->num_nodes))
502 		return -EINVAL;
503 
504 	mutex_lock(&icc_lock);
505 
506 	old_avg = path->reqs[0].avg_bw;
507 	old_peak = path->reqs[0].peak_bw;
508 
509 	for (i = 0; i < path->num_nodes; i++) {
510 		node = path->reqs[i].node;
511 
512 		/* update the consumer request for this path */
513 		path->reqs[i].avg_bw = avg_bw;
514 		path->reqs[i].peak_bw = peak_bw;
515 
516 		/* aggregate requests for this node */
517 		aggregate_requests(node);
518 
519 		trace_icc_set_bw(path, node, i, avg_bw, peak_bw);
520 	}
521 
522 	ret = apply_constraints(path);
523 	if (ret) {
524 		pr_debug("interconnect: error applying constraints (%d)\n",
525 			 ret);
526 
527 		for (i = 0; i < path->num_nodes; i++) {
528 			node = path->reqs[i].node;
529 			path->reqs[i].avg_bw = old_avg;
530 			path->reqs[i].peak_bw = old_peak;
531 			aggregate_requests(node);
532 		}
533 		apply_constraints(path);
534 	}
535 
536 	mutex_unlock(&icc_lock);
537 
538 	trace_icc_set_bw_end(path, ret);
539 
540 	return ret;
541 }
542 EXPORT_SYMBOL_GPL(icc_set_bw);
543 
544 /**
545  * icc_get() - return a handle for path between two endpoints
546  * @dev: the device requesting the path
547  * @src_id: source device port id
548  * @dst_id: destination device port id
549  *
550  * This function will search for a path between two endpoints and return an
551  * icc_path handle on success. Use icc_put() to release
552  * constraints when they are not needed anymore.
553  * If the interconnect API is disabled, NULL is returned and the consumer
554  * drivers will still build. Drivers are free to handle this specifically,
555  * but they don't have to.
556  *
557  * Return: icc_path pointer on success, ERR_PTR() on error or NULL if the
558  * interconnect API is disabled.
559  */
560 struct icc_path *icc_get(struct device *dev, const int src_id, const int dst_id)
561 {
562 	struct icc_node *src, *dst;
563 	struct icc_path *path = ERR_PTR(-EPROBE_DEFER);
564 
565 	mutex_lock(&icc_lock);
566 
567 	src = node_find(src_id);
568 	if (!src)
569 		goto out;
570 
571 	dst = node_find(dst_id);
572 	if (!dst)
573 		goto out;
574 
575 	path = path_find(dev, src, dst);
576 	if (IS_ERR(path)) {
577 		dev_err(dev, "%s: invalid path=%ld\n", __func__, PTR_ERR(path));
578 		goto out;
579 	}
580 
581 	path->name = kasprintf(GFP_KERNEL, "%s-%s", src->name, dst->name);
582 out:
583 	mutex_unlock(&icc_lock);
584 	return path;
585 }
586 EXPORT_SYMBOL_GPL(icc_get);
587 
588 /**
589  * icc_put() - release the reference to the icc_path
590  * @path: interconnect path
591  *
592  * Use this function to release the constraints on a path when the path is
593  * no longer needed. The constraints will be re-aggregated.
594  */
595 void icc_put(struct icc_path *path)
596 {
597 	struct icc_node *node;
598 	size_t i;
599 	int ret;
600 
601 	if (!path || WARN_ON(IS_ERR(path)))
602 		return;
603 
604 	ret = icc_set_bw(path, 0, 0);
605 	if (ret)
606 		pr_err("%s: error (%d)\n", __func__, ret);
607 
608 	mutex_lock(&icc_lock);
609 	for (i = 0; i < path->num_nodes; i++) {
610 		node = path->reqs[i].node;
611 		hlist_del(&path->reqs[i].req_node);
612 		if (!WARN_ON(!node->provider->users))
613 			node->provider->users--;
614 	}
615 	mutex_unlock(&icc_lock);
616 
617 	kfree_const(path->name);
618 	kfree(path);
619 }
620 EXPORT_SYMBOL_GPL(icc_put);
621 
622 static struct icc_node *icc_node_create_nolock(int id)
623 {
624 	struct icc_node *node;
625 
626 	/* check if node already exists */
627 	node = node_find(id);
628 	if (node)
629 		return node;
630 
631 	node = kzalloc(sizeof(*node), GFP_KERNEL);
632 	if (!node)
633 		return ERR_PTR(-ENOMEM);
634 
635 	id = idr_alloc(&icc_idr, node, id, id + 1, GFP_KERNEL);
636 	if (id < 0) {
637 		WARN(1, "%s: couldn't get idr\n", __func__);
638 		kfree(node);
639 		return ERR_PTR(id);
640 	}
641 
642 	node->id = id;
643 
644 	return node;
645 }
646 
647 /**
648  * icc_node_create() - create a node
649  * @id: node id
650  *
651  * Return: icc_node pointer on success, or ERR_PTR() on error
652  */
653 struct icc_node *icc_node_create(int id)
654 {
655 	struct icc_node *node;
656 
657 	mutex_lock(&icc_lock);
658 
659 	node = icc_node_create_nolock(id);
660 
661 	mutex_unlock(&icc_lock);
662 
663 	return node;
664 }
665 EXPORT_SYMBOL_GPL(icc_node_create);
666 
667 /**
668  * icc_node_destroy() - destroy a node
669  * @id: node id
670  */
671 void icc_node_destroy(int id)
672 {
673 	struct icc_node *node;
674 
675 	mutex_lock(&icc_lock);
676 
677 	node = node_find(id);
678 	if (node) {
679 		idr_remove(&icc_idr, node->id);
680 		WARN_ON(!hlist_empty(&node->req_list));
681 	}
682 
683 	mutex_unlock(&icc_lock);
684 
685 	kfree(node);
686 }
687 EXPORT_SYMBOL_GPL(icc_node_destroy);
688 
689 /**
690  * icc_link_create() - create a link between two nodes
691  * @node: source node id
692  * @dst_id: destination node id
693  *
694  * Create a link between two nodes. The nodes might belong to different
695  * interconnect providers and the @dst_id node might not exist (if the
696  * provider driver has not probed yet). So just create the @dst_id node
697  * and when the actual provider driver is probed, the rest of the node
698  * data is filled.
699  *
700  * Return: 0 on success, or an error code otherwise
701  */
702 int icc_link_create(struct icc_node *node, const int dst_id)
703 {
704 	struct icc_node *dst;
705 	struct icc_node **new;
706 	int ret = 0;
707 
708 	if (!node->provider)
709 		return -EINVAL;
710 
711 	mutex_lock(&icc_lock);
712 
713 	dst = node_find(dst_id);
714 	if (!dst) {
715 		dst = icc_node_create_nolock(dst_id);
716 
717 		if (IS_ERR(dst)) {
718 			ret = PTR_ERR(dst);
719 			goto out;
720 		}
721 	}
722 
723 	new = krealloc(node->links,
724 		       (node->num_links + 1) * sizeof(*node->links),
725 		       GFP_KERNEL);
726 	if (!new) {
727 		ret = -ENOMEM;
728 		goto out;
729 	}
730 
731 	node->links = new;
732 	node->links[node->num_links++] = dst;
733 
734 out:
735 	mutex_unlock(&icc_lock);
736 
737 	return ret;
738 }
739 EXPORT_SYMBOL_GPL(icc_link_create);
740 
741 /**
742  * icc_link_destroy() - destroy a link between two nodes
743  * @src: pointer to source node
744  * @dst: pointer to destination node
745  *
746  * Return: 0 on success, or an error code otherwise
747  */
748 int icc_link_destroy(struct icc_node *src, struct icc_node *dst)
749 {
750 	struct icc_node **new;
751 	size_t slot;
752 	int ret = 0;
753 
754 	if (IS_ERR_OR_NULL(src))
755 		return -EINVAL;
756 
757 	if (IS_ERR_OR_NULL(dst))
758 		return -EINVAL;
759 
760 	mutex_lock(&icc_lock);
761 
762 	for (slot = 0; slot < src->num_links; slot++)
763 		if (src->links[slot] == dst)
764 			break;
765 
766 	if (WARN_ON(slot == src->num_links)) {
767 		ret = -ENXIO;
768 		goto out;
769 	}
770 
771 	src->links[slot] = src->links[--src->num_links];
772 
773 	new = krealloc(src->links, src->num_links * sizeof(*src->links),
774 		       GFP_KERNEL);
775 	if (new)
776 		src->links = new;
777 
778 out:
779 	mutex_unlock(&icc_lock);
780 
781 	return ret;
782 }
783 EXPORT_SYMBOL_GPL(icc_link_destroy);
784 
785 /**
786  * icc_node_add() - add interconnect node to interconnect provider
787  * @node: pointer to the interconnect node
788  * @provider: pointer to the interconnect provider
789  */
790 void icc_node_add(struct icc_node *node, struct icc_provider *provider)
791 {
792 	mutex_lock(&icc_lock);
793 
794 	node->provider = provider;
795 	list_add_tail(&node->node_list, &provider->nodes);
796 
797 	mutex_unlock(&icc_lock);
798 }
799 EXPORT_SYMBOL_GPL(icc_node_add);
800 
801 /**
802  * icc_node_del() - delete interconnect node from interconnect provider
803  * @node: pointer to the interconnect node
804  */
805 void icc_node_del(struct icc_node *node)
806 {
807 	mutex_lock(&icc_lock);
808 
809 	list_del(&node->node_list);
810 
811 	mutex_unlock(&icc_lock);
812 }
813 EXPORT_SYMBOL_GPL(icc_node_del);
814 
815 /**
816  * icc_nodes_remove() - remove all previously added nodes from provider
817  * @provider: the interconnect provider we are removing nodes from
818  *
819  * Return: 0 on success, or an error code otherwise
820  */
821 int icc_nodes_remove(struct icc_provider *provider)
822 {
823 	struct icc_node *n, *tmp;
824 
825 	if (WARN_ON(IS_ERR_OR_NULL(provider)))
826 		return -EINVAL;
827 
828 	list_for_each_entry_safe_reverse(n, tmp, &provider->nodes, node_list) {
829 		icc_node_del(n);
830 		icc_node_destroy(n->id);
831 	}
832 
833 	return 0;
834 }
835 EXPORT_SYMBOL_GPL(icc_nodes_remove);
836 
837 /**
838  * icc_provider_add() - add a new interconnect provider
839  * @provider: the interconnect provider that will be added into topology
840  *
841  * Return: 0 on success, or an error code otherwise
842  */
843 int icc_provider_add(struct icc_provider *provider)
844 {
845 	if (WARN_ON(!provider->set))
846 		return -EINVAL;
847 	if (WARN_ON(!provider->xlate))
848 		return -EINVAL;
849 
850 	mutex_lock(&icc_lock);
851 
852 	INIT_LIST_HEAD(&provider->nodes);
853 	list_add_tail(&provider->provider_list, &icc_providers);
854 
855 	mutex_unlock(&icc_lock);
856 
857 	dev_dbg(provider->dev, "interconnect provider added to topology\n");
858 
859 	return 0;
860 }
861 EXPORT_SYMBOL_GPL(icc_provider_add);
862 
863 /**
864  * icc_provider_del() - delete previously added interconnect provider
865  * @provider: the interconnect provider that will be removed from topology
866  *
867  * Return: 0 on success, or an error code otherwise
868  */
869 int icc_provider_del(struct icc_provider *provider)
870 {
871 	mutex_lock(&icc_lock);
872 	if (provider->users) {
873 		pr_warn("interconnect provider still has %d users\n",
874 			provider->users);
875 		mutex_unlock(&icc_lock);
876 		return -EBUSY;
877 	}
878 
879 	if (!list_empty(&provider->nodes)) {
880 		pr_warn("interconnect provider still has nodes\n");
881 		mutex_unlock(&icc_lock);
882 		return -EBUSY;
883 	}
884 
885 	list_del(&provider->provider_list);
886 	mutex_unlock(&icc_lock);
887 
888 	return 0;
889 }
890 EXPORT_SYMBOL_GPL(icc_provider_del);
891 
892 static int __init icc_init(void)
893 {
894 	icc_debugfs_dir = debugfs_create_dir("interconnect", NULL);
895 	debugfs_create_file("interconnect_summary", 0444,
896 			    icc_debugfs_dir, NULL, &icc_summary_fops);
897 	debugfs_create_file("interconnect_graph", 0444,
898 			    icc_debugfs_dir, NULL, &icc_graph_fops);
899 	return 0;
900 }
901 
902 static void __exit icc_exit(void)
903 {
904 	debugfs_remove_recursive(icc_debugfs_dir);
905 }
906 module_init(icc_init);
907 module_exit(icc_exit);
908 
909 MODULE_AUTHOR("Georgi Djakov <georgi.djakov@linaro.org>");
910 MODULE_DESCRIPTION("Interconnect Driver Core");
911 MODULE_LICENSE("GPL v2");
912