[v6,1/8] interconnect: Add generic on-chip interconnect API

Message ID 20180709155104.25528-2-georgi.djakov@linaro.org
State New
Headers show
Series
  • [v6,1/8] interconnect: Add generic on-chip interconnect API
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Commit Message

Georgi Djakov July 9, 2018, 3:50 p.m.
This patch introduces a new API to get requirements and configure the
interconnect buses across the entire chipset to fit with the current
demand.

The API is using a consumer/provider-based model, where the providers are
the interconnect buses and the consumers could be various drivers.
The consumers request interconnect resources (path) between endpoints and
set the desired constraints on this data flow path. The providers receive
requests from consumers and aggregate these requests for all master-slave
pairs on that path. Then the providers configure each participating in the
topology node according to the requested data flow path, physical links and
constraints. The topology could be complicated and multi-tiered and is SoC
specific.

Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>

---
 Documentation/interconnect/interconnect.rst |  96 ++++
 drivers/Kconfig                             |   2 +
 drivers/Makefile                            |   1 +
 drivers/interconnect/Kconfig                |  10 +
 drivers/interconnect/Makefile               |   2 +
 drivers/interconnect/core.c                 | 597 ++++++++++++++++++++
 include/linux/interconnect-provider.h       | 130 +++++
 include/linux/interconnect.h                |  42 ++
 8 files changed, 880 insertions(+)
 create mode 100644 Documentation/interconnect/interconnect.rst
 create mode 100644 drivers/interconnect/Kconfig
 create mode 100644 drivers/interconnect/Makefile
 create mode 100644 drivers/interconnect/core.c
 create mode 100644 include/linux/interconnect-provider.h
 create mode 100644 include/linux/interconnect.h

Comments

Alexandre Bailon July 11, 2018, 3:05 p.m. | #1
Hi Georgi,

On 07/09/2018 05:50 PM, Georgi Djakov wrote:
> This patch introduces a new API to get requirements and configure the

> interconnect buses across the entire chipset to fit with the current

> demand.

> 

> The API is using a consumer/provider-based model, where the providers are

> the interconnect buses and the consumers could be various drivers.

> The consumers request interconnect resources (path) between endpoints and

> set the desired constraints on this data flow path. The providers receive

> requests from consumers and aggregate these requests for all master-slave

> pairs on that path. Then the providers configure each participating in the

> topology node according to the requested data flow path, physical links and

> constraints. The topology could be complicated and multi-tiered and is SoC

> specific.

> 

> Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>

> ---

>  Documentation/interconnect/interconnect.rst |  96 ++++

>  drivers/Kconfig                             |   2 +

>  drivers/Makefile                            |   1 +

>  drivers/interconnect/Kconfig                |  10 +

>  drivers/interconnect/Makefile               |   2 +

>  drivers/interconnect/core.c                 | 597 ++++++++++++++++++++

>  include/linux/interconnect-provider.h       | 130 +++++

>  include/linux/interconnect.h                |  42 ++

>  8 files changed, 880 insertions(+)

>  create mode 100644 Documentation/interconnect/interconnect.rst

>  create mode 100644 drivers/interconnect/Kconfig

>  create mode 100644 drivers/interconnect/Makefile

>  create mode 100644 drivers/interconnect/core.c

>  create mode 100644 include/linux/interconnect-provider.h

>  create mode 100644 include/linux/interconnect.h

> 

> diff --git a/Documentation/interconnect/interconnect.rst b/Documentation/interconnect/interconnect.rst

> new file mode 100644

> index 000000000000..a1ebd83ad0a1

> --- /dev/null

> +++ b/Documentation/interconnect/interconnect.rst

> @@ -0,0 +1,96 @@

> +.. SPDX-License-Identifier: GPL-2.0

> +

> +=====================================

> +GENERIC SYSTEM INTERCONNECT SUBSYSTEM

> +=====================================

> +

> +Introduction

> +------------

> +

> +This framework is designed to provide a standard kernel interface to control

> +the settings of the interconnects on a SoC. These settings can be throughput,

> +latency and priority between multiple interconnected devices or functional

> +blocks. This can be controlled dynamically in order to save power or provide

> +maximum performance.

> +

> +The interconnect bus is a hardware with configurable parameters, which can be

> +set on a data path according to the requests received from various drivers.

> +An example of interconnect buses are the interconnects between various

> +components or functional blocks in chipsets. There can be multiple interconnects

> +on a SoC that can be multi-tiered.

> +

> +Below is a simplified diagram of a real-world SoC interconnect bus topology.

> +

> +::

> +

> + +----------------+    +----------------+

> + | HW Accelerator |--->|      M NoC     |<---------------+

> + +----------------+    +----------------+                |

> +                         |      |                    +------------+

> +  +-----+  +-------------+      V       +------+     |            |

> +  | DDR |  |                +--------+  | PCIe |     |            |

> +  +-----+  |                | Slaves |  +------+     |            |

> +    ^ ^    |                +--------+     |         |   C NoC    |

> +    | |    V                               V         |            |

> + +------------------+   +------------------------+   |            |   +-----+

> + |                  |-->|                        |-->|            |-->| CPU |

> + |                  |-->|                        |<--|            |   +-----+

> + |     Mem NoC      |   |         S NoC          |   +------------+

> + |                  |<--|                        |---------+    |

> + |                  |<--|                        |<------+ |    |   +--------+

> + +------------------+   +------------------------+       | |    +-->| Slaves |

> +   ^  ^    ^    ^          ^                             | |        +--------+

> +   |  |    |    |          |                             | V

> + +------+  |  +-----+   +-----+  +---------+   +----------------+   +--------+

> + | CPUs |  |  | GPU |   | DSP |  | Masters |-->|       P NoC    |-->| Slaves |

> + +------+  |  +-----+   +-----+  +---------+   +----------------+   +--------+

> +           |

> +       +-------+

> +       | Modem |

> +       +-------+

> +

> +Terminology

> +-----------

> +

> +Interconnect provider is the software definition of the interconnect hardware.

> +The interconnect providers on the above diagram are M NoC, S NoC, C NoC, P NoC

> +and Mem NoC.

> +

> +Interconnect node is the software definition of the interconnect hardware

> +port. Each interconnect provider consists of multiple interconnect nodes,

> +which are connected to other SoC components including other interconnect

> +providers. The point on the diagram where the CPUs connects to the memory is

> +called an interconnect node, which belongs to the Mem NoC interconnect provider.

> +

> +Interconnect endpoints are the first or the last element of the path. Every

> +endpoint is a node, but not every node is an endpoint.

> +

> +Interconnect path is everything between two endpoints including all the nodes

> +that have to be traversed to reach from a source to destination node. It may

> +include multiple master-slave pairs across several interconnect providers.

> +

> +Interconnect consumers are the entities which make use of the data paths exposed

> +by the providers. The consumers send requests to providers requesting various

> +throughput, latency and priority. Usually the consumers are device drivers, that

> +send request based on their needs. An example for a consumer is a video decoder

> +that supports various formats and image sizes.

> +

> +Interconnect providers

> +----------------------

> +

> +Interconnect provider is an entity that implements methods to initialize and

> +configure a interconnect bus hardware. The interconnect provider drivers should

> +be registered with the interconnect provider core.

> +

> +The interconnect framework provider API functions are documented in

> +.. kernel-doc:: include/linux/interconnect-provider.h

> +

> +Interconnect consumers

> +----------------------

> +

> +Interconnect consumers are the clients which use the interconnect APIs to

> +get paths between endpoints and set their bandwidth/latency/QoS requirements

> +for these interconnect paths.

> +

> +The interconnect framework consumer API functions are documented in

> +.. kernel-doc:: include/linux/interconnect.h

> diff --git a/drivers/Kconfig b/drivers/Kconfig

> index 95b9ccc08165..3ed6ede9d021 100644

> --- a/drivers/Kconfig

> +++ b/drivers/Kconfig

> @@ -217,4 +217,6 @@ source "drivers/siox/Kconfig"

>  

>  source "drivers/slimbus/Kconfig"

>  

> +source "drivers/interconnect/Kconfig"

> +

>  endmenu

> diff --git a/drivers/Makefile b/drivers/Makefile

> index 24cd47014657..0cca95740d9b 100644

> --- a/drivers/Makefile

> +++ b/drivers/Makefile

> @@ -185,3 +185,4 @@ obj-$(CONFIG_TEE)		+= tee/

>  obj-$(CONFIG_MULTIPLEXER)	+= mux/

>  obj-$(CONFIG_UNISYS_VISORBUS)	+= visorbus/

>  obj-$(CONFIG_SIOX)		+= siox/

> +obj-$(CONFIG_INTERCONNECT)	+= interconnect/

> diff --git a/drivers/interconnect/Kconfig b/drivers/interconnect/Kconfig

> new file mode 100644

> index 000000000000..a261c7d41deb

> --- /dev/null

> +++ b/drivers/interconnect/Kconfig

> @@ -0,0 +1,10 @@

> +menuconfig INTERCONNECT

> +	tristate "On-Chip Interconnect management support"

> +	help

> +	  Support for management of the on-chip interconnects.

> +

> +	  This framework is designed to provide a generic interface for

> +	  managing the interconnects in a SoC.

> +

> +	  If unsure, say no.

> +

> diff --git a/drivers/interconnect/Makefile b/drivers/interconnect/Makefile

> new file mode 100644

> index 000000000000..97fca2e09d24

> --- /dev/null

> +++ b/drivers/interconnect/Makefile

> @@ -0,0 +1,2 @@

> +# SPDX-License-Identifier: GPL-2.0

> +obj-$(CONFIG_INTERCONNECT)		+= core.o

> diff --git a/drivers/interconnect/core.c b/drivers/interconnect/core.c

> new file mode 100644

> index 000000000000..63707c3c3d48

> --- /dev/null

> +++ b/drivers/interconnect/core.c

> @@ -0,0 +1,597 @@

> +// SPDX-License-Identifier: GPL-2.0

> +/*

> + * Interconnect framework core driver

> + *

> + * Copyright (c) 2018, Linaro Ltd.

> + * Author: Georgi Djakov <georgi.djakov@linaro.org>

> + */

> +

> +#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>

> +

> +static DEFINE_IDR(icc_idr);

> +static LIST_HEAD(icc_provider_list);

> +static DEFINE_MUTEX(icc_lock);

> +

> +/**

> + * 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[];

> +};

> +

> +static struct icc_node *node_find(const int id)

> +{

> +	return idr_find(&icc_idr, id);

> +}

> +

> +static struct icc_path *path_init(struct device *dev, struct icc_node *dst,

> +				  ssize_t num_nodes)

> +{

> +	struct icc_node *node = dst;

> +	struct icc_path *path;

> +	size_t i;

> +

> +	path = kzalloc(struct_size(path, reqs, num_nodes), 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;

> +		path->reqs[i].dev = dev;

> +		/* 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 = 1;

> +	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 including 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)

> +			n->is_traversed = false;

> +

> +	if (found) {

> +		struct icc_path *path = path_init(dev, dst, depth);

> +

> +		if (IS_ERR(path))

> +			return path;

> +

> +		for (i = 0; i < path->num_nodes; i++) {

> +			node = path->reqs[i].node;

> +			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;

> +	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);

> +

> +		/* set the constraints */

> +		ret = p->set(prev, next, p->avg_bw, p->peak_bw);

> +		if (ret)

> +			goto out;

> +	}

> +out:

> +	return ret;

> +}

> +

> +/**

> + * 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;

> +

> +	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);

> +

> +	mutex_lock(&icc_lock);

> +

> +	src = node_find(src_id);

> +	if (!src)

> +		goto out;

> +

> +	dst = node_find(dst_id);

> +	if (!dst)

> +		goto out;

> +

> +	path = path_find(dev, src, dst);

> +	if (IS_ERR(path))

> +		dev_err(dev, "%s: invalid path=%ld\n", __func__, PTR_ERR(path));

> +

> +out:

> +	mutex_unlock(&icc_lock);

> +	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(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);

> +

> +static struct icc_node *icc_node_create_nolock(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;

> +	}

> +

> +	id = idr_alloc(&icc_idr, node, id, id + 1, GFP_KERNEL);

> +	if (WARN(id < 0, "couldn't get idr")) {

> +		kfree(node);

> +		node = ERR_PTR(id);

> +		goto out;

> +	}

> +

> +	node->id = id;

> +

> +out:

> +	return node;

> +}

> +

> +/**

> + * 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;

> +

> +	mutex_lock(&icc_lock);

> +

> +	node = icc_node_create_nolock(id);

> +

> +	mutex_unlock(&icc_lock);

> +

> +	return node;

> +}

> +EXPORT_SYMBOL_GPL(icc_node_create);

> +

> +/**

> + * icc_node_destroy() - destroy a node

> + * @id: node id

> + *

> + */

> +void icc_node_destroy(int id)

> +{

> +	struct icc_node *node;

> +

> +	node = node_find(id);

> +	if (node) {

> +		mutex_lock(&icc_lock);

> +		idr_remove(&icc_idr, node->id);

> +		WARN_ON(!hlist_empty(&node->req_list));

> +		mutex_unlock(&icc_lock);

> +	}

> +

> +	kfree(node);

> +}

> +EXPORT_SYMBOL_GPL(icc_node_destroy);

> +

> +/**

> + * 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;

> +

> +	mutex_lock(&icc_lock);

> +

> +	dst = node_find(dst_id);

> +	if (!dst) {

> +		dst = icc_node_create_nolock(dst_id);

> +

> +		if (IS_ERR(dst)) {

> +			ret = PTR_ERR(dst);

> +			goto out;

> +		}

> +	}

> +

> +	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_destroy() - destroy 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_destroy(struct icc_node *src, struct icc_node *dst)

> +{

> +	struct icc_node **new;

> +	struct icc_node *last;

> +	int ret = 0;

> +	size_t slot;

> +

> +	if (IS_ERR_OR_NULL(src))

> +		return -EINVAL;

> +

> +	if (IS_ERR_OR_NULL(dst))

> +		return -EINVAL;

> +

> +	mutex_lock(&icc_lock);

> +

> +	for (slot = 0; slot < src->num_links; slot++)

> +		if (src->links[slot] == dst)

> +			break;

> +

> +	last = src->links[src->num_links];

> +

> +	new = krealloc(src->links,

> +		       (src->num_links - 1) * sizeof(*src->links),

> +		       GFP_KERNEL);

> +	if (!new) {

> +		ret = -ENOMEM;

> +		goto out;

> +	}

> +

> +	src->links = new;

> +

> +	if (slot < src->num_links - 1)

> +		/* move the last element to the slot that was freed */

> +		src->links[slot] = last;

> +

> +	src->num_links--;

> +

> +out:

> +	mutex_unlock(&icc_lock);

> +

> +	return ret;

> +}

> +EXPORT_SYMBOL_GPL(icc_link_destroy);

> +

> +/**

> + * icc_node_add() - add interconnect node to interconnect provider

> + * @node: pointer to the interconnect node

> + * @provider: pointer to the interconnect provider

> + *

> + */

> +void 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);

> +}

> +EXPORT_SYMBOL_GPL(icc_node_add);

> +

> +/**

> + * icc_node_del() - delete interconnect node from interconnect provider

> + * @node: pointer to the interconnect node

> + *

> + */

> +void icc_node_del(struct icc_node *node)

> +{

> +	mutex_lock(&icc_lock);

> +

> +	list_del(&node->node_list);

> +

> +	mutex_unlock(&icc_lock);

> +}

> +EXPORT_SYMBOL_GPL(icc_node_del);

> +

> +/**

> + * 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;I think you should also check provider->aggregate here.

> +

> +	mutex_lock(&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(&provider->nodes)) {

> +		pr_warn("interconnect provider still has nodes\n");

> +		mutex_unlock(&icc_lock);

> +		return -EBUSY;

> +	}

> +

> +	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");

> diff --git a/include/linux/interconnect-provider.h b/include/linux/interconnect-provider.h

> new file mode 100644

> index 000000000000..c78aa930bcab

> --- /dev/null

> +++ b/include/linux/interconnect-provider.h

> @@ -0,0 +1,130 @@

> +/* SPDX-License-Identifier: GPL-2.0 */

> +/*

> + * Copyright (c) 2018, Linaro Ltd.

> + * Author: Georgi Djakov <georgi.djakov@linaro.org>

> + */

> +

> +#ifndef _LINUX_INTERCONNECT_PROVIDER_H

> +#define _LINUX_INTERCONNECT_PROVIDER_H

> +

> +#include <linux/interconnect.h>

> +

> +#define icc_units_to_bps(bw)  ((bw) * 1000ULL)

> +

> +struct icc_node;

> +

> +/**

> + * struct icc_provider - interconnect provider (controller) entity that might

> + * provide multiple interconnect controls

> + *

> + * @provider_list: list of the registered interconnect providers

> + * @nodes: internal list of the interconnect provider nodes

> + * @set: pointer to device specific set operation function

> + * @aggregate: pointer to device specific aggregate operation function

> + * @dev: the device this interconnect provider belongs to

> + * @users: count of active users

> + * @avg_bw: aggregated value of average bandwidth requests from all nodes

> + * @peak_bw: aggregated value of peak bandwidth requests from all nodes

> + * @data: pointer to private data

> + */

> +struct icc_provider {

> +	struct list_head	provider_list;

> +	struct list_head	nodes;

> +	int (*set)(struct icc_node *src, struct icc_node *dst,

> +		   u32 avg_bw, u32 peak_bw);

> +	int (*aggregate)(struct icc_node *node, u32 avg_bw, u32 peak_bw,

> +			 u32 *agg_avg, u32 *agg_peak);

> +	struct device		*dev;

> +	int			users;

> +	u32			avg_bw;

> +	u32			peak_bw;

> +	void			*data;

> +};

> +

> +/**

> + * struct icc_node - entity that is part of the interconnect topology

> + *

> + * @id: platform specific node id

> + * @name: node name used in debugfs

> + * @links: a list of targets pointing to where we can go next when traversing

> + * @num_links: number of links to other interconnect nodes

> + * @provider: points to the interconnect provider of this node

> + * @node_list: the list entry in the parent provider's "nodes" list

> + * @search_list: list used when walking the nodes graph

> + * @reverse: pointer to previous node when walking the nodes graph

> + * @is_traversed: flag that is used when walking the nodes graph

> + * @req_list: a list of QoS constraint requests associated with this node

> + * @avg_bw: aggregated value of average bandwidth requests from all consumers

> + * @peak_bw: aggregated value of peak bandwidth requests from all consumers

> + * @data: pointer to private data

> + */

> +struct icc_node {

> +	int			id;

> +	const char              *name;

> +	struct icc_node		**links;

> +	size_t			num_links;

> +

> +	struct icc_provider	*provider;

> +	struct list_head	node_list;

> +	struct list_head	search_list;

> +	struct icc_node		*reverse;

> +	bool			is_traversed;

> +	struct hlist_head	req_list;

> +	u32			avg_bw;

> +	u32			peak_bw;

> +	void			*data;

> +};

> +

> +#if IS_ENABLED(CONFIG_INTERCONNECT)

> +

> +struct icc_node *icc_node_create(int id);

> +void icc_node_destroy(int id);

> +int icc_link_create(struct icc_node *node, const int dst_id);

> +int icc_link_destroy(struct icc_node *src, struct icc_node *dst);

> +void icc_node_add(struct icc_node *node, struct icc_provider *provider);

> +void icc_node_del(struct icc_node *node);

> +int icc_provider_add(struct icc_provider *provider);

> +int icc_provider_del(struct icc_provider *provider);

> +

> +#else

> +

> +static inline struct icc_node *icc_node_create(int id)

> +{

> +	return ERR_PTR(-ENOTSUPP);

> +}

> +

> +void icc_node_destroy(int id)

> +{

> +}

> +

> +static inline int icc_link_create(struct icc_node *node, const int dst_id)

> +{

> +	return -ENOTSUPP;

> +}

> +

> +int icc_link_destroy(struct icc_node *src, struct icc_node *dst)

> +{

> +	return -ENOTSUPP;

> +}

> +

> +void icc_node_add(struct icc_node *node, struct icc_provider *provider)

> +{

> +}

> +

> +void icc_node_del(struct icc_node *node)

> +{

> +}

> +

> +static inline int icc_provider_add(struct icc_provider *provider)

> +{

> +	return -ENOTSUPP;

> +}

> +

> +static inline int icc_provider_del(struct icc_provider *provider)

> +{

> +	return -ENOTSUPP;

> +}

> +

> +#endif /* CONFIG_INTERCONNECT */

> +

> +#endif /* _LINUX_INTERCONNECT_PROVIDER_H */

> diff --git a/include/linux/interconnect.h b/include/linux/interconnect.h

> new file mode 100644

> index 000000000000..593215371fd6

> --- /dev/null

> +++ b/include/linux/interconnect.h

> @@ -0,0 +1,42 @@

> +/* SPDX-License-Identifier: GPL-2.0 */

> +/*

> + * Copyright (c) 2018, Linaro Ltd.

> + * Author: Georgi Djakov <georgi.djakov@linaro.org>

> + */

> +

> +#ifndef _LINUX_INTERCONNECT_H

> +#define _LINUX_INTERCONNECT_H

> +

> +#include <linux/mutex.h>

> +#include <linux/types.h>

> +

> +struct icc_path;

> +struct device;

> +

> +#if IS_ENABLED(CONFIG_INTERCONNECT)

> +

> +struct icc_path *icc_get(struct device *dev, const int src_id,

> +			 const int dst_id);

> +void icc_put(struct icc_path *path);

> +int icc_set(struct icc_path *path, u32 avg_bw, u32 peak_bw);

> +

> +#else

> +

> +static inline struct icc_path *icc_get(struct device *dev, const int src_id,

> +				       const int dst_id)

> +{

> +	return NULL;

> +}

> +

> +static inline void icc_put(struct icc_path *path)

> +{

> +}

> +

> +static inline int icc_set(struct icc_path *path, u32 avg_bw, u32 peak_bw)

> +{

> +	return 0;

> +}

> +

> +#endif /* CONFIG_INTERCONNECT */

> +

> +#endif /* _LINUX_INTERCONNECT_H */

>
Georgi Djakov July 20, 2018, 2:31 p.m. | #2
Hi Evan,

Thanks for helping to improve this!

On 07/11/2018 01:34 AM, Evan Green wrote:
> Ahoy Georgi!

> On Mon, Jul 9, 2018 at 8:51 AM Georgi Djakov <georgi.djakov@linaro.org> wrote:

>>

>> This patch introduces a new API to get requirements and configure the

>> interconnect buses across the entire chipset to fit with the current

>> demand.

>>

>> The API is using a consumer/provider-based model, where the providers are

>> the interconnect buses and the consumers could be various drivers.

>> The consumers request interconnect resources (path) between endpoints and

>> set the desired constraints on this data flow path. The providers receive

>> requests from consumers and aggregate these requests for all master-slave

>> pairs on that path. Then the providers configure each participating in the

>> topology node according to the requested data flow path, physical links and

>> constraints. The topology could be complicated and multi-tiered and is SoC

>> specific.

>>

>> Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>

>> ---


[..]

>> +Interconnect node is the software definition of the interconnect hardware

>> +port. Each interconnect provider consists of multiple interconnect nodes,

>> +which are connected to other SoC components including other interconnect

>> +providers. The point on the diagram where the CPUs connects to the memory is

> 

> CPUs connect


Ok.

[..]

>> +

>> +#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>

> 

> I needed to add #include <linux/overflow.h> to get struct_size() (used

> in path_init) in order to get this to compile, but maybe my kernel is

> missing some upstream picks.


Yes, should be included.

>> +#include <linux/slab.h>

>> +

>> +static DEFINE_IDR(icc_idr);

>> +static LIST_HEAD(icc_provider_list);

>> +static DEFINE_MUTEX(icc_lock);

>> +

>> +/**

>> + * 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[];

>> +};

>> +

>> +static struct icc_node *node_find(const int id)

>> +{

>> +       return idr_find(&icc_idr, id);

> 

> Wasn't there going to be a warning if the mutex is not held?


I think that it would be really useful if the functions are exported,
but for now let's skip it.

>> +}

>> +

>> +static struct icc_path *path_init(struct device *dev, struct icc_node *dst,

>> +                                 ssize_t num_nodes)

>> +{

>> +       struct icc_node *node = dst;

>> +       struct icc_path *path;

>> +       size_t i;

>> +

>> +       path = kzalloc(struct_size(path, reqs, num_nodes), GFP_KERNEL);

>> +       if (!path)

>> +               return ERR_PTR(-ENOMEM);

>> +

>> +       path->num_nodes = num_nodes;

>> +

> 

> There should probably also be a warning here about holding the lock,

> since you're modifying node->req_list.


This is called only by path_find() with the lock held.

>> +       for (i = 0; i < num_nodes; i++) {

>> +               hlist_add_head(&path->reqs[i].req_node, &node->req_list);

>> +

>> +               path->reqs[i].node = node;

>> +               path->reqs[i].dev = dev;

>> +               /* 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 = 1;

>> +       bool found = false;

>> +       int ret = -EPROBE_DEFER;

>> +

>> +       INIT_LIST_HEAD(&traverse_list);

>> +       INIT_LIST_HEAD(&edge_list);

>> +       INIT_LIST_HEAD(&visited_list);

>> +

> 

> A warning here too about holding the lock would also be good, since

> multiple people in here at once would be bad.


This is only called by icc_get() with locked mutex.

>> +       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 including 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)

>> +                       n->is_traversed = false;

> 

> I think I missed this on the last round. I thought you had been

> keeping visited_list specifically so you could use it to reset

> is_traversed here. But now it looks like you're going through the

> entire graph. What happened?


Hm, will review and fix.

>> +

>> +       if (found) {

>> +               struct icc_path *path = path_init(dev, dst, depth);

>> +

>> +               if (IS_ERR(path))

>> +                       return path;

>> +

>> +               for (i = 0; i < path->num_nodes; i++) {

>> +                       node = path->reqs[i].node;

>> +                       node->provider->users++;

> 

> Hm, should this go in path_init as well? What do you think? You sort

> of become a user once you tack your path.req_node on the

> node.req_list.


Ok, will move it.

>> +               }

>> +               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;

>> +}

> 

> This doesn't have to be addressed in this series, but I wonder if the

> aggregate() callback should be made aware of whether its aggregating

> requests within a node, or nodes within a provider? Right now the

> aggregate callback has no way of knowing what it's aggregating for; I

> guess the question is: might it need to? I'm unsure.


Currently the platforms that would be using this do not need this
differentiation, but this can be revised if needed in the future.

>> +

>> +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;

>> +       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);

>> +

>> +               /* set the constraints */

>> +               ret = p->set(prev, next, p->avg_bw, p->peak_bw);

>> +               if (ret)

>> +                       goto out;

>> +       }

>> +out:

>> +       return ret;

>> +}

>> +

>> +/**

>> + * 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;

>> +

>> +       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);

>> +

>> +       mutex_lock(&icc_lock);

>> +

>> +       src = node_find(src_id);

>> +       if (!src)

>> +               goto out;

>> +

>> +       dst = node_find(dst_id);

>> +       if (!dst)

>> +               goto out;

>> +

>> +       path = path_find(dev, src, dst);

>> +       if (IS_ERR(path))

>> +               dev_err(dev, "%s: invalid path=%ld\n", __func__, PTR_ERR(path));

>> +

>> +out:

>> +       mutex_unlock(&icc_lock);

>> +       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(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);

>> +

> 

> Maybe a warning if users is zero?


Yes, good idea.

>> +               node->provider->users--;

>> +       }

>> +       mutex_unlock(&icc_lock);

>> +

>> +       kfree(path);

>> +}

>> +EXPORT_SYMBOL_GPL(icc_put);

>> +

>> +static struct icc_node *icc_node_create_nolock(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;

>> +       }

>> +

>> +       id = idr_alloc(&icc_idr, node, id, id + 1, GFP_KERNEL);

>> +       if (WARN(id < 0, "couldn't get idr")) {

>> +               kfree(node);

>> +               node = ERR_PTR(id);

>> +               goto out;

>> +       }

>> +

>> +       node->id = id;

>> +

>> +out:

>> +       return node;

>> +}

>> +

>> +/**

>> + * 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;

>> +

>> +       mutex_lock(&icc_lock);

>> +

>> +       node = icc_node_create_nolock(id);

>> +

>> +       mutex_unlock(&icc_lock);

>> +

>> +       return node;

>> +}

>> +EXPORT_SYMBOL_GPL(icc_node_create);

>> +

>> +/**

>> + * icc_node_destroy() - destroy a node

>> + * @id: node id

>> + *

>> + */

>> +void icc_node_destroy(int id)

>> +{

>> +       struct icc_node *node;

>> +

>> +       node = node_find(id);

>> +       if (node) {

>> +               mutex_lock(&icc_lock);

> 

> mutex_lock should be moved above node_find, since node_find needs the lock held.


Ok.

>> +               idr_remove(&icc_idr, node->id);

>> +               WARN_ON(!hlist_empty(&node->req_list));

>> +               mutex_unlock(&icc_lock);

>> +       }

>> +

>> +       kfree(node);

>> +}

>> +EXPORT_SYMBOL_GPL(icc_node_destroy);

>> +

>> +/**

>> + * 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;

>> +

>> +       mutex_lock(&icc_lock);

>> +

>> +       dst = node_find(dst_id);

>> +       if (!dst) {

>> +               dst = icc_node_create_nolock(dst_id);

>> +

>> +               if (IS_ERR(dst)) {

>> +                       ret = PTR_ERR(dst);

>> +                       goto out;

>> +               }

>> +       }

>> +

>> +       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_destroy() - destroy 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_destroy(struct icc_node *src, struct icc_node *dst)

>> +{

>> +       struct icc_node **new;

>> +       struct icc_node *last;

>> +       int ret = 0;

>> +       size_t slot;

>> +

>> +       if (IS_ERR_OR_NULL(src))

>> +               return -EINVAL;

>> +

>> +       if (IS_ERR_OR_NULL(dst))

>> +               return -EINVAL;

>> +

>> +       mutex_lock(&icc_lock);

>> +

>> +       for (slot = 0; slot < src->num_links; slot++)

>> +               if (src->links[slot] == dst)

>> +                       break;

>> +

> 

> How about a warning or failure if slot == src->num_links, meaning

> someone is trying to tear down a link they never set up.


Ok.

>> +       last = src->links[src->num_links];

> 

> Shouldn't it be src->num_links - 1?


Yes, indeed.

>> +

>> +       new = krealloc(src->links,

>> +                      (src->num_links - 1) * sizeof(*src->links),

>> +                      GFP_KERNEL);

>> +       if (!new) {

>> +               ret = -ENOMEM;

>> +               goto out;

> 

> It's technically not really a problem if this realloc fails, right?

> Your old array should still be valid, and it's big enough to hold

> everything you wanted. Just only assign src->link = new if realloc

> succeeds.

> 

>> +       }

>> +

>> +       src->links = new;

>> +

>> +       if (slot < src->num_links - 1)

>> +               /* move the last element to the slot that was freed */

>> +               src->links[slot] = last;

> 

> If you moved this above the realloc, then you could do away with the

> conditional part of it, since at worst it would end up being:

> src->links[num_links - 1] = src->links[num_links - 1]; which is a

> no-op. You also wouldn't need the "last" local either.


Ok. Will simplify it!

Thanks,
Georgi

Patch

diff --git a/Documentation/interconnect/interconnect.rst b/Documentation/interconnect/interconnect.rst
new file mode 100644
index 000000000000..a1ebd83ad0a1
--- /dev/null
+++ b/Documentation/interconnect/interconnect.rst
@@ -0,0 +1,96 @@ 
+.. SPDX-License-Identifier: GPL-2.0
+
+=====================================
+GENERIC SYSTEM INTERCONNECT SUBSYSTEM
+=====================================
+
+Introduction
+------------
+
+This framework is designed to provide a standard kernel interface to control
+the settings of the interconnects on a SoC. These settings can be throughput,
+latency and priority between multiple interconnected devices or functional
+blocks. This can be controlled dynamically in order to save power or provide
+maximum performance.
+
+The interconnect bus is a hardware with configurable parameters, which can be
+set on a data path according to the requests received from various drivers.
+An example of interconnect buses are the interconnects between various
+components or functional blocks in chipsets. There can be multiple interconnects
+on a SoC that can be multi-tiered.
+
+Below is a simplified diagram of a real-world SoC interconnect bus topology.
+
+::
+
+ +----------------+    +----------------+
+ | HW Accelerator |--->|      M NoC     |<---------------+
+ +----------------+    +----------------+                |
+                         |      |                    +------------+
+  +-----+  +-------------+      V       +------+     |            |
+  | DDR |  |                +--------+  | PCIe |     |            |
+  +-----+  |                | Slaves |  +------+     |            |
+    ^ ^    |                +--------+     |         |   C NoC    |
+    | |    V                               V         |            |
+ +------------------+   +------------------------+   |            |   +-----+
+ |                  |-->|                        |-->|            |-->| CPU |
+ |                  |-->|                        |<--|            |   +-----+
+ |     Mem NoC      |   |         S NoC          |   +------------+
+ |                  |<--|                        |---------+    |
+ |                  |<--|                        |<------+ |    |   +--------+
+ +------------------+   +------------------------+       | |    +-->| Slaves |
+   ^  ^    ^    ^          ^                             | |        +--------+
+   |  |    |    |          |                             | V
+ +------+  |  +-----+   +-----+  +---------+   +----------------+   +--------+
+ | CPUs |  |  | GPU |   | DSP |  | Masters |-->|       P NoC    |-->| Slaves |
+ +------+  |  +-----+   +-----+  +---------+   +----------------+   +--------+
+           |
+       +-------+
+       | Modem |
+       +-------+
+
+Terminology
+-----------
+
+Interconnect provider is the software definition of the interconnect hardware.
+The interconnect providers on the above diagram are M NoC, S NoC, C NoC, P NoC
+and Mem NoC.
+
+Interconnect node is the software definition of the interconnect hardware
+port. Each interconnect provider consists of multiple interconnect nodes,
+which are connected to other SoC components including other interconnect
+providers. The point on the diagram where the CPUs connects to the memory is
+called an interconnect node, which belongs to the Mem NoC interconnect provider.
+
+Interconnect endpoints are the first or the last element of the path. Every
+endpoint is a node, but not every node is an endpoint.
+
+Interconnect path is everything between two endpoints including all the nodes
+that have to be traversed to reach from a source to destination node. It may
+include multiple master-slave pairs across several interconnect providers.
+
+Interconnect consumers are the entities which make use of the data paths exposed
+by the providers. The consumers send requests to providers requesting various
+throughput, latency and priority. Usually the consumers are device drivers, that
+send request based on their needs. An example for a consumer is a video decoder
+that supports various formats and image sizes.
+
+Interconnect providers
+----------------------
+
+Interconnect provider is an entity that implements methods to initialize and
+configure a interconnect bus hardware. The interconnect provider drivers should
+be registered with the interconnect provider core.
+
+The interconnect framework provider API functions are documented in
+.. kernel-doc:: include/linux/interconnect-provider.h
+
+Interconnect consumers
+----------------------
+
+Interconnect consumers are the clients which use the interconnect APIs to
+get paths between endpoints and set their bandwidth/latency/QoS requirements
+for these interconnect paths.
+
+The interconnect framework consumer API functions are documented in
+.. kernel-doc:: include/linux/interconnect.h
diff --git a/drivers/Kconfig b/drivers/Kconfig
index 95b9ccc08165..3ed6ede9d021 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -217,4 +217,6 @@  source "drivers/siox/Kconfig"
 
 source "drivers/slimbus/Kconfig"
 
+source "drivers/interconnect/Kconfig"
+
 endmenu
diff --git a/drivers/Makefile b/drivers/Makefile
index 24cd47014657..0cca95740d9b 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -185,3 +185,4 @@  obj-$(CONFIG_TEE)		+= tee/
 obj-$(CONFIG_MULTIPLEXER)	+= mux/
 obj-$(CONFIG_UNISYS_VISORBUS)	+= visorbus/
 obj-$(CONFIG_SIOX)		+= siox/
+obj-$(CONFIG_INTERCONNECT)	+= interconnect/
diff --git a/drivers/interconnect/Kconfig b/drivers/interconnect/Kconfig
new file mode 100644
index 000000000000..a261c7d41deb
--- /dev/null
+++ b/drivers/interconnect/Kconfig
@@ -0,0 +1,10 @@ 
+menuconfig INTERCONNECT
+	tristate "On-Chip Interconnect management support"
+	help
+	  Support for management of the on-chip interconnects.
+
+	  This framework is designed to provide a generic interface for
+	  managing the interconnects in a SoC.
+
+	  If unsure, say no.
+
diff --git a/drivers/interconnect/Makefile b/drivers/interconnect/Makefile
new file mode 100644
index 000000000000..97fca2e09d24
--- /dev/null
+++ b/drivers/interconnect/Makefile
@@ -0,0 +1,2 @@ 
+# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_INTERCONNECT)		+= core.o
diff --git a/drivers/interconnect/core.c b/drivers/interconnect/core.c
new file mode 100644
index 000000000000..63707c3c3d48
--- /dev/null
+++ b/drivers/interconnect/core.c
@@ -0,0 +1,597 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Interconnect framework core driver
+ *
+ * Copyright (c) 2018, Linaro Ltd.
+ * Author: Georgi Djakov <georgi.djakov@linaro.org>
+ */
+
+#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>
+
+static DEFINE_IDR(icc_idr);
+static LIST_HEAD(icc_provider_list);
+static DEFINE_MUTEX(icc_lock);
+
+/**
+ * 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[];
+};
+
+static struct icc_node *node_find(const int id)
+{
+	return idr_find(&icc_idr, id);
+}
+
+static struct icc_path *path_init(struct device *dev, struct icc_node *dst,
+				  ssize_t num_nodes)
+{
+	struct icc_node *node = dst;
+	struct icc_path *path;
+	size_t i;
+
+	path = kzalloc(struct_size(path, reqs, num_nodes), 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;
+		path->reqs[i].dev = dev;
+		/* 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 = 1;
+	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 including 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)
+			n->is_traversed = false;
+
+	if (found) {
+		struct icc_path *path = path_init(dev, dst, depth);
+
+		if (IS_ERR(path))
+			return path;
+
+		for (i = 0; i < path->num_nodes; i++) {
+			node = path->reqs[i].node;
+			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;
+	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);
+
+		/* set the constraints */
+		ret = p->set(prev, next, p->avg_bw, p->peak_bw);
+		if (ret)
+			goto out;
+	}
+out:
+	return ret;
+}
+
+/**
+ * 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;
+
+	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);
+
+	mutex_lock(&icc_lock);
+
+	src = node_find(src_id);
+	if (!src)
+		goto out;
+
+	dst = node_find(dst_id);
+	if (!dst)
+		goto out;
+
+	path = path_find(dev, src, dst);
+	if (IS_ERR(path))
+		dev_err(dev, "%s: invalid path=%ld\n", __func__, PTR_ERR(path));
+
+out:
+	mutex_unlock(&icc_lock);
+	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(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);
+
+static struct icc_node *icc_node_create_nolock(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;
+	}
+
+	id = idr_alloc(&icc_idr, node, id, id + 1, GFP_KERNEL);
+	if (WARN(id < 0, "couldn't get idr")) {
+		kfree(node);
+		node = ERR_PTR(id);
+		goto out;
+	}
+
+	node->id = id;
+
+out:
+	return node;
+}
+
+/**
+ * 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;
+
+	mutex_lock(&icc_lock);
+
+	node = icc_node_create_nolock(id);
+
+	mutex_unlock(&icc_lock);
+
+	return node;
+}
+EXPORT_SYMBOL_GPL(icc_node_create);
+
+/**
+ * icc_node_destroy() - destroy a node
+ * @id: node id
+ *
+ */
+void icc_node_destroy(int id)
+{
+	struct icc_node *node;
+
+	node = node_find(id);
+	if (node) {
+		mutex_lock(&icc_lock);
+		idr_remove(&icc_idr, node->id);
+		WARN_ON(!hlist_empty(&node->req_list));
+		mutex_unlock(&icc_lock);
+	}
+
+	kfree(node);
+}
+EXPORT_SYMBOL_GPL(icc_node_destroy);
+
+/**
+ * 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;
+
+	mutex_lock(&icc_lock);
+
+	dst = node_find(dst_id);
+	if (!dst) {
+		dst = icc_node_create_nolock(dst_id);
+
+		if (IS_ERR(dst)) {
+			ret = PTR_ERR(dst);
+			goto out;
+		}
+	}
+
+	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_destroy() - destroy 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_destroy(struct icc_node *src, struct icc_node *dst)
+{
+	struct icc_node **new;
+	struct icc_node *last;
+	int ret = 0;
+	size_t slot;
+
+	if (IS_ERR_OR_NULL(src))
+		return -EINVAL;
+
+	if (IS_ERR_OR_NULL(dst))
+		return -EINVAL;
+
+	mutex_lock(&icc_lock);
+
+	for (slot = 0; slot < src->num_links; slot++)
+		if (src->links[slot] == dst)
+			break;
+
+	last = src->links[src->num_links];
+
+	new = krealloc(src->links,
+		       (src->num_links - 1) * sizeof(*src->links),
+		       GFP_KERNEL);
+	if (!new) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	src->links = new;
+
+	if (slot < src->num_links - 1)
+		/* move the last element to the slot that was freed */
+		src->links[slot] = last;
+
+	src->num_links--;
+
+out:
+	mutex_unlock(&icc_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(icc_link_destroy);
+
+/**
+ * icc_node_add() - add interconnect node to interconnect provider
+ * @node: pointer to the interconnect node
+ * @provider: pointer to the interconnect provider
+ *
+ */
+void 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);
+}
+EXPORT_SYMBOL_GPL(icc_node_add);
+
+/**
+ * icc_node_del() - delete interconnect node from interconnect provider
+ * @node: pointer to the interconnect node
+ *
+ */
+void icc_node_del(struct icc_node *node)
+{
+	mutex_lock(&icc_lock);
+
+	list_del(&node->node_list);
+
+	mutex_unlock(&icc_lock);
+}
+EXPORT_SYMBOL_GPL(icc_node_del);
+
+/**
+ * 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_lock(&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(&provider->nodes)) {
+		pr_warn("interconnect provider still has nodes\n");
+		mutex_unlock(&icc_lock);
+		return -EBUSY;
+	}
+
+	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");
diff --git a/include/linux/interconnect-provider.h b/include/linux/interconnect-provider.h
new file mode 100644
index 000000000000..c78aa930bcab
--- /dev/null
+++ b/include/linux/interconnect-provider.h
@@ -0,0 +1,130 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2018, Linaro Ltd.
+ * Author: Georgi Djakov <georgi.djakov@linaro.org>
+ */
+
+#ifndef _LINUX_INTERCONNECT_PROVIDER_H
+#define _LINUX_INTERCONNECT_PROVIDER_H
+
+#include <linux/interconnect.h>
+
+#define icc_units_to_bps(bw)  ((bw) * 1000ULL)
+
+struct icc_node;
+
+/**
+ * struct icc_provider - interconnect provider (controller) entity that might
+ * provide multiple interconnect controls
+ *
+ * @provider_list: list of the registered interconnect providers
+ * @nodes: internal list of the interconnect provider nodes
+ * @set: pointer to device specific set operation function
+ * @aggregate: pointer to device specific aggregate operation function
+ * @dev: the device this interconnect provider belongs to
+ * @users: count of active users
+ * @avg_bw: aggregated value of average bandwidth requests from all nodes
+ * @peak_bw: aggregated value of peak bandwidth requests from all nodes
+ * @data: pointer to private data
+ */
+struct icc_provider {
+	struct list_head	provider_list;
+	struct list_head	nodes;
+	int (*set)(struct icc_node *src, struct icc_node *dst,
+		   u32 avg_bw, u32 peak_bw);
+	int (*aggregate)(struct icc_node *node, u32 avg_bw, u32 peak_bw,
+			 u32 *agg_avg, u32 *agg_peak);
+	struct device		*dev;
+	int			users;
+	u32			avg_bw;
+	u32			peak_bw;
+	void			*data;
+};
+
+/**
+ * struct icc_node - entity that is part of the interconnect topology
+ *
+ * @id: platform specific node id
+ * @name: node name used in debugfs
+ * @links: a list of targets pointing to where we can go next when traversing
+ * @num_links: number of links to other interconnect nodes
+ * @provider: points to the interconnect provider of this node
+ * @node_list: the list entry in the parent provider's "nodes" list
+ * @search_list: list used when walking the nodes graph
+ * @reverse: pointer to previous node when walking the nodes graph
+ * @is_traversed: flag that is used when walking the nodes graph
+ * @req_list: a list of QoS constraint requests associated with this node
+ * @avg_bw: aggregated value of average bandwidth requests from all consumers
+ * @peak_bw: aggregated value of peak bandwidth requests from all consumers
+ * @data: pointer to private data
+ */
+struct icc_node {
+	int			id;
+	const char              *name;
+	struct icc_node		**links;
+	size_t			num_links;
+
+	struct icc_provider	*provider;
+	struct list_head	node_list;
+	struct list_head	search_list;
+	struct icc_node		*reverse;
+	bool			is_traversed;
+	struct hlist_head	req_list;
+	u32			avg_bw;
+	u32			peak_bw;
+	void			*data;
+};
+
+#if IS_ENABLED(CONFIG_INTERCONNECT)
+
+struct icc_node *icc_node_create(int id);
+void icc_node_destroy(int id);
+int icc_link_create(struct icc_node *node, const int dst_id);
+int icc_link_destroy(struct icc_node *src, struct icc_node *dst);
+void icc_node_add(struct icc_node *node, struct icc_provider *provider);
+void icc_node_del(struct icc_node *node);
+int icc_provider_add(struct icc_provider *provider);
+int icc_provider_del(struct icc_provider *provider);
+
+#else
+
+static inline struct icc_node *icc_node_create(int id)
+{
+	return ERR_PTR(-ENOTSUPP);
+}
+
+void icc_node_destroy(int id)
+{
+}
+
+static inline int icc_link_create(struct icc_node *node, const int dst_id)
+{
+	return -ENOTSUPP;
+}
+
+int icc_link_destroy(struct icc_node *src, struct icc_node *dst)
+{
+	return -ENOTSUPP;
+}
+
+void icc_node_add(struct icc_node *node, struct icc_provider *provider)
+{
+}
+
+void icc_node_del(struct icc_node *node)
+{
+}
+
+static inline int icc_provider_add(struct icc_provider *provider)
+{
+	return -ENOTSUPP;
+}
+
+static inline int icc_provider_del(struct icc_provider *provider)
+{
+	return -ENOTSUPP;
+}
+
+#endif /* CONFIG_INTERCONNECT */
+
+#endif /* _LINUX_INTERCONNECT_PROVIDER_H */
diff --git a/include/linux/interconnect.h b/include/linux/interconnect.h
new file mode 100644
index 000000000000..593215371fd6
--- /dev/null
+++ b/include/linux/interconnect.h
@@ -0,0 +1,42 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2018, Linaro Ltd.
+ * Author: Georgi Djakov <georgi.djakov@linaro.org>
+ */
+
+#ifndef _LINUX_INTERCONNECT_H
+#define _LINUX_INTERCONNECT_H
+
+#include <linux/mutex.h>
+#include <linux/types.h>
+
+struct icc_path;
+struct device;
+
+#if IS_ENABLED(CONFIG_INTERCONNECT)
+
+struct icc_path *icc_get(struct device *dev, const int src_id,
+			 const int dst_id);
+void icc_put(struct icc_path *path);
+int icc_set(struct icc_path *path, u32 avg_bw, u32 peak_bw);
+
+#else
+
+static inline struct icc_path *icc_get(struct device *dev, const int src_id,
+				       const int dst_id)
+{
+	return NULL;
+}
+
+static inline void icc_put(struct icc_path *path)
+{
+}
+
+static inline int icc_set(struct icc_path *path, u32 avg_bw, u32 peak_bw)
+{
+	return 0;
+}
+
+#endif /* CONFIG_INTERCONNECT */
+
+#endif /* _LINUX_INTERCONNECT_H */