path: root/drivers/interconnect/core.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Interconnect framework core driver
 *
 * Copyright (c) 2018, Linaro Ltd.
 * Author: Georgi Djakov <georgi.djakov@linaro.org>
 */

#include <linux/debugfs.h>
#include <linux/device.h>
#include <linux/idr.h>
#include <linux/init.h>
#include <linux/interconnect.h>
#include <linux/interconnect-provider.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/of.h>
#include <linux/uaccess.h>

static DEFINE_IDR(icc_idr);
static LIST_HEAD(icc_provider_list);
static DEFINE_MUTEX(icc_lock);
static struct dentry *icc_debugfs_dir;

/**
 * struct icc_req - constraints that are attached to each node
 *
 * @req_node: entry in list of requests for the particular @node
 * @node: the interconnect node to which this constraint applies
 * @dev: reference to the device that sets the constraints
 * @avg_bw: an integer describing the average bandwidth in kbps
 * @peak_bw: an integer describing the peak bandwidth in kbps
 */
struct icc_req {
	struct hlist_node req_node;
	struct icc_node *node;
	struct device *dev;
	u32 avg_bw;
	u32 peak_bw;
};

/**
 * struct icc_path - interconnect path structure
 * @num_nodes: number of hops (nodes)
 * @reqs: array of the requests applicable to this path of nodes
 */
struct icc_path {
	size_t num_nodes;
	struct icc_req reqs[0];
};

#ifdef CONFIG_DEBUG_FS

static void icc_summary_show_one(struct seq_file *s, struct icc_node *n)
{
	if (!n)
		return;

	seq_printf(s, "%-30s %12d %12d\n",
		   n->name, n->avg_bw, n->peak_bw);
}

static int icc_summary_show(struct seq_file *s, void *data)
{
	struct icc_provider *provider;

	seq_puts(s, " node                                   avg         peak\n");
	seq_puts(s, "--------------------------------------------------------\n");

	mutex_lock(&icc_lock);

	list_for_each_entry(provider, &icc_provider_list, provider_list) {
		struct icc_node *n;

		list_for_each_entry(n, &provider->nodes, node_list) {
			struct icc_req *r;

			icc_summary_show_one(s, n);
			hlist_for_each_entry(r, &n->req_list, req_node) {
				if (!r->dev)
					continue;

				seq_printf(s, "    %-26s %12d %12d\n",
					   dev_name(r->dev), r->avg_bw,
					   r->peak_bw);
			}
		}
	}

	mutex_unlock(&icc_lock);

	return 0;
}

static int icc_summary_open(struct inode *inode, struct file *file)
{
	return single_open(file, icc_summary_show, inode->i_private);
}

static const struct file_operations icc_summary_fops = {
	.open		= icc_summary_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= single_release,
};

static int __init icc_debugfs_init(void)
{
	struct dentry *file;

	icc_debugfs_dir = debugfs_create_dir("interconnect", NULL);
	if (!icc_debugfs_dir) {
		pr_err("interconnect: error creating debugfs directory\n");
		return -ENODEV;
	}

	file = debugfs_create_file("interconnect_summary", 0444,
				   icc_debugfs_dir, NULL, &icc_summary_fops);
	if (!file)
		return -ENODEV;

	return 0;
}
late_initcall(icc_debugfs_init);
#endif

static struct icc_node *node_find(const int id)
{
	struct icc_node *node;

	mutex_lock(&icc_lock);
	node = idr_find(&icc_idr, id);
	mutex_unlock(&icc_lock);

	return node;
}

static struct icc_path *path_allocate(struct icc_node *dst, ssize_t num_nodes)
{
	struct icc_node *node = dst;
	struct icc_path *path;
	size_t i;

	path = kzalloc(sizeof(*path) + num_nodes * sizeof(*path->reqs),
		       GFP_KERNEL);
	if (!path)
		return ERR_PTR(-ENOMEM);

	path->num_nodes = num_nodes;

	for (i = 0; i < num_nodes; i++) {
		hlist_add_head(&path->reqs[i].req_node, &node->req_list);

		path->reqs[i].node = node;
		/* reference to previous node was saved during path traversal */
		node = node->reverse;
	}

	return path;
}

static struct icc_path *path_find(struct device *dev, struct icc_node *src,
				  struct icc_node *dst)
{
	struct icc_node *n, *node = NULL;
	struct icc_provider *provider;
	struct list_head traverse_list;
	struct list_head edge_list;
	struct list_head visited_list;
	size_t i, depth = 0;
	bool found = false;
	int ret = -EPROBE_DEFER;

	INIT_LIST_HEAD(&traverse_list);
	INIT_LIST_HEAD(&edge_list);
	INIT_LIST_HEAD(&visited_list);

	list_add_tail(&src->search_list, &traverse_list);
	src->reverse = NULL;

	do {
		list_for_each_entry_safe(node, n, &traverse_list, search_list) {
			if (node == dst) {
				found = true;
				list_add(&node->search_list, &visited_list);
				break;
			}
			for (i = 0; i < node->num_links; i++) {
				struct icc_node *tmp = node->links[i];

				if (!tmp) {
					ret = -ENOENT;
					goto out;
				}

				if (tmp->is_traversed)
					continue;

				tmp->is_traversed = true;
				tmp->reverse = node;
				list_add(&tmp->search_list, &edge_list);
			}
		}
		if (found)
			break;

		list_splice_init(&traverse_list, &visited_list);
		list_splice_init(&edge_list, &traverse_list);

		/* count the hops away from the source */
		depth++;

	} while (!list_empty(&traverse_list));

out:
	/* reset the traversed state */
	list_for_each_entry(provider, &icc_provider_list, provider_list) {
		list_for_each_entry(n, &provider->nodes, node_list)
			if (n->is_traversed)
				n->is_traversed = false;
	}

	if (found) {
		struct icc_path *path = path_allocate(dst, depth);

		if (IS_ERR(path))
			return path;

		/* initialize the path */
		for (i = 0; i < path->num_nodes; i++) {
			node = path->reqs[i].node;
			path->reqs[i].dev = dev;
			node->provider->users++;
		}
		return path;
	}

	return ERR_PTR(ret);
}

/*
 * We want the path to honor all bandwidth requests, so the average
 * bandwidth requirements from each consumer are aggregated at each node
 * and provider level. By default the average bandwidth is the sum of all
 * averages and the peak will be the highest of all peak bandwidth requests.
 */

static int aggregate_requests(struct icc_node *node)
{
	struct icc_provider *p = node->provider;
	struct icc_req *r;

	node->avg_bw = 0;
	node->peak_bw = 0;

	hlist_for_each_entry(r, &node->req_list, req_node)
		p->aggregate(node, r->avg_bw, r->peak_bw,
			     &node->avg_bw, &node->peak_bw);

	return 0;
}

static void aggregate_provider(struct icc_provider *p)
{
	struct icc_node *n;

	p->avg_bw = 0;
	p->peak_bw = 0;

	list_for_each_entry(n, &p->nodes, node_list)
		p->aggregate(n, n->avg_bw, n->peak_bw,
			     &p->avg_bw, &p->peak_bw);
}

static int apply_constraints(struct icc_path *path)
{
	struct icc_node *next, *prev = NULL;
	int ret = 0;
	int i;

	for (i = 0; i < path->num_nodes; i++, prev = next) {
		struct icc_provider *p;

		next = path->reqs[i].node;
		/*
		 * Both endpoints should be valid master-slave pairs of the
		 * same interconnect provider that will be configured.
		 */
		if (!prev || next->provider != prev->provider)
			continue;

		p = next->provider;

		aggregate_provider(p);

		if (p->set) {
			/* set the constraints */
			ret = p->set(prev, next, p->avg_bw, p->peak_bw);
		}

		if (ret)
			goto out;
	}
out:
	return ret;
}

struct icc_path *of_icc_get(struct device *dev, const char *name)
{
	struct device_node *np = NULL;
	struct of_phandle_args src_args, dst_args;
	u32 src_id, dst_id;
	int idx = 0;
	int ret;

	if (!dev || !dev->of_node)
		return ERR_PTR(-ENODEV);

	np = dev->of_node;

	/*
	 * When the consumer DT node do not have "interconnects" property
	 * return a NULL path to skip setting constraints.
	 */
	if (!of_find_property(np, "interconnects", NULL))
		return NULL;

	/*
	 * We use a combination of phandle and specifier for endpoint. For now
	 * lets support only global ids and extend this is the future if needed
	 * without breaking DT compatibility.
	 */
	if (name) {
		idx = of_property_match_string(np, "interconnect-names", name);
		if (idx < 0)
			return ERR_PTR(idx);
	}

	ret = of_parse_phandle_with_args(np, "interconnects",
					 "#interconnect-cells", idx * 2,
					 &src_args);
	if (ret)
		return ERR_PTR(ret);

	of_node_put(src_args.np);

	if (!src_args.args_count || src_args.args_count > 1)
		return ERR_PTR(-EINVAL);

	src_id = src_args.args[0];

	ret = of_parse_phandle_with_args(np, "interconnects",
					 "#interconnect-cells", idx * 2 + 1,
					 &dst_args);
	if (ret)
		return ERR_PTR(ret);

	of_node_put(dst_args.np);

	if (!dst_args.args_count || dst_args.args_count > 1)
		return ERR_PTR(-EINVAL);

	dst_id = dst_args.args[0];

	return icc_get(dev, src_id, dst_id);
}
EXPORT_SYMBOL_GPL(of_icc_get);

/**
 * icc_set() - set constraints on an interconnect path between two endpoints
 * @path: reference to the path returned by icc_get()
 * @avg_bw: average bandwidth in kbps
 * @peak_bw: peak bandwidth in kbps
 *
 * This function is used by an interconnect consumer to express its own needs
 * in terms of bandwidth for a previously requested path between two endpoints.
 * The requests are aggregated and each node is updated accordingly. The entire
 * path is locked by a mutex to ensure that the set() is completed.
 * The @path can be NULL when the "interconnects" DT properties is missing,
 * which will mean that no constraints will be set.
 *
 * Returns 0 on success, or an appropriate error code otherwise.
 */
int icc_set(struct icc_path *path, u32 avg_bw, u32 peak_bw)
{
	struct icc_node *node;
	struct icc_provider *p;
	size_t i;
	int ret = 0;

	if (!path)
		return 0;

	mutex_lock(&icc_lock);

	for (i = 0; i < path->num_nodes; i++) {
		node = path->reqs[i].node;
		p = node->provider;

		/* update the consumer request for this path */
		path->reqs[i].avg_bw = avg_bw;
		path->reqs[i].peak_bw = peak_bw;

		/* aggregate requests for this node */
		aggregate_requests(node);
	}

	ret = apply_constraints(path);
	if (ret)
		pr_err("interconnect: error applying constraints (%d)", ret);

	mutex_unlock(&icc_lock);

	return ret;
}
EXPORT_SYMBOL_GPL(icc_set);

/**
 * icc_get() - return a handle for path between two endpoints
 * @dev: the device requesting the path
 * @src_id: source device port id
 * @dst_id: destination device port id
 *
 * This function will search for a path between two endpoints and return an
 * icc_path handle on success. Use icc_put() to release
 * constraints when the they are not needed anymore.
 *
 * Return: icc_path pointer on success, or ERR_PTR() on error
 */
struct icc_path *icc_get(struct device *dev, const int src_id, const int dst_id)
{
	struct icc_node *src, *dst;
	struct icc_path *path = ERR_PTR(-EPROBE_DEFER);

	src = node_find(src_id);
	if (!src)
		goto out;

	dst = node_find(dst_id);
	if (!dst)
		goto out;

	mutex_lock(&icc_lock);
	path = path_find(dev, src, dst);
	mutex_unlock(&icc_lock);
	if (IS_ERR(path)) {
		dev_err(dev, "%s: invalid path=%ld\n", __func__, PTR_ERR(path));
		goto out;
	}

out:
	return path;
}
EXPORT_SYMBOL_GPL(icc_get);

/**
 * icc_put() - release the reference to the icc_path
 * @path: interconnect path
 *
 * Use this function to release the constraints on a path when the path is
 * no longer needed. The constraints will be re-aggregated.
 */
void icc_put(struct icc_path *path)
{
	struct icc_node *node;
	size_t i;
	int ret;

	if (!path || WARN_ON_ONCE(IS_ERR(path)))
		return;

	ret = icc_set(path, 0, 0);
	if (ret)
		pr_err("%s: error (%d)\n", __func__, ret);

	mutex_lock(&icc_lock);
	for (i = 0; i < path->num_nodes; i++) {
		node = path->reqs[i].node;
		hlist_del(&path->reqs[i].req_node);

		node->provider->users--;
	}
	mutex_unlock(&icc_lock);

	kfree(path);
}
EXPORT_SYMBOL_GPL(icc_put);

/**
 * icc_node_create() - create a node
 * @id: node id
 *
 * Return: icc_node pointer on success, or ERR_PTR() on error
 */
struct icc_node *icc_node_create(int id)
{
	struct icc_node *node;

	/* check if node already exists */
	node = node_find(id);
	if (node)
		goto out;

	node = kzalloc(sizeof(*node), GFP_KERNEL);
	if (!node) {
		node = ERR_PTR(-ENOMEM);
		goto out;
	}

	mutex_lock(&icc_lock);

	id = idr_alloc(&icc_idr, node, id, id + 1, GFP_KERNEL);
	if (WARN(id < 0, "couldn't get idr")) {
		node = ERR_PTR(id);
		goto out;
	}

	node->id = id;

out:
	mutex_unlock(&icc_lock);

	return node;
}
EXPORT_SYMBOL_GPL(icc_node_create);

/**
 * icc_node_remove() - remove a node
 * @id: node id
 *
 */
void icc_node_remove(int id)
{
	struct icc_node *node;

	node = node_find(id);
	if (node) {
		mutex_lock(&icc_lock);
		idr_remove(&icc_idr, node->id);
		mutex_unlock(&icc_lock);
	}

	kfree(node);
}
EXPORT_SYMBOL_GPL(icc_node_remove);

/**
 * icc_link_create() - create a link between two nodes
 * @src_id: source node id
 * @dst_id: destination node id
 *
 * Create a link between two nodes. The nodes might belong to different
 * interconnect providers and the @dst_id node might not exist (if the
 * provider driver has not probed yet). So just create the @dst_id node
 * and when the actual provider driver is probed, the rest of the node
 * data is filled.
 *
 * Return: 0 on success, or an error code otherwise
 */
int icc_link_create(struct icc_node *node, const int dst_id)
{
	struct icc_node *dst;
	struct icc_node **new;
	int ret = 0;

	if (!node->provider)
		return -EINVAL;

	dst = node_find(dst_id);
	if (!dst) {
		dst = icc_node_create(dst_id);

		if (IS_ERR(dst)) {
			ret = PTR_ERR(dst);
			goto out;
		}
	}

	mutex_lock(&icc_lock);

	new = krealloc(node->links,
		       (node->num_links + 1) * sizeof(*node->links),
		       GFP_KERNEL);
	if (!new) {
		ret = -ENOMEM;
		goto out;
	}

	node->links = new;
	node->links[node->num_links++] = dst;

out:
	mutex_unlock(&icc_lock);

	return ret;
}
EXPORT_SYMBOL_GPL(icc_link_create);

/**
 * icc_link_remove() - remove a link between two nodes
 * @src: pointer to source node
 * @dst: pointer to destination node
 *
 * Return: 0 on success, or an error code otherwise
 */
int icc_link_remove(struct icc_node *src, struct icc_node *dst)
{
	struct icc_node **new;
	int ret = 0;
	int i, j;

	if (IS_ERR_OR_NULL(src))
		return PTR_ERR(src);

	if (IS_ERR_OR_NULL(dst))
		return PTR_ERR(dst);

	mutex_lock(&icc_lock);

	new = krealloc(src->links,
		       (src->num_links - 1) * sizeof(*src->links),
		       GFP_KERNEL);
	if (!new) {
		ret = -ENOMEM;
		goto out;
	}

	for (i = 0, j = 0; j < src->num_links; j++) {
		if (src->links[j] == dst)
			continue;

		new[i++] = src->links[j];
	}

	src->links = new;
	src->num_links--;

out:
	mutex_unlock(&icc_lock);

	return ret;
}
EXPORT_SYMBOL_GPL(icc_link_remove);

/**
 * icc_node_add() - add an interconnect node to interconnect provider
 * @node: pointer to the interconnect node
 * @provider: pointer to the interconnect provider
 *
 * Return: 0 on success, or an error code otherwise
 */
int icc_node_add(struct icc_node *node, struct icc_provider *provider)
{
	mutex_lock(&icc_lock);

	node->provider = provider;
	list_add(&node->node_list, &provider->nodes);

	mutex_unlock(&icc_lock);

	return 0;
}
EXPORT_SYMBOL_GPL(icc_node_add);

/**
 * icc_provider_add() - add a new interconnect provider
 * @icc_provider: the interconnect provider that will be added into topology
 *
 * Return: 0 on success, or an error code otherwise
 */
int icc_provider_add(struct icc_provider *provider)
{
	if (WARN_ON(!provider->set))
		return -EINVAL;

	mutex_init(&icc_lock);

	INIT_LIST_HEAD(&provider->nodes);
	list_add(&provider->provider_list, &icc_provider_list);

	mutex_unlock(&icc_lock);

	dev_dbg(provider->dev, "interconnect provider added to topology\n");

	return 0;
}
EXPORT_SYMBOL_GPL(icc_provider_add);

/**
 * icc_provider_del() - delete previously added interconnect provider
 * @icc_provider: the interconnect provider that will be removed from topology
 *
 * Return: 0 on success, or an error code otherwise
 */
int icc_provider_del(struct icc_provider *provider)
{
	mutex_lock(&icc_lock);
	if (provider->users) {
		pr_warn("interconnect provider still has %d users\n",
			provider->users);
		mutex_unlock(&icc_lock);
		return -EBUSY;
	}

	if (!list_empty_careful(&provider->nodes)) {
		pr_warn("interconnect provider still has nodes\n");
		mutex_unlock(&icc_lock);
		return -EEXIST;
	}

	list_del(&provider->provider_list);
	mutex_unlock(&icc_lock);

	return 0;
}
EXPORT_SYMBOL_GPL(icc_provider_del);

MODULE_AUTHOR("Georgi Djakov <georgi.djakov@linaro.org");
MODULE_DESCRIPTION("Interconnect Driver Core");
MODULE_LICENSE("GPL v2");