[RFC,v0,1/2] interconnect: Add generic interconnect controller API

diff --git a/Documentation/devicetree/bindings/interconnect/interconnect.txt b/Documentation/devicetree/bindings/interconnect/interconnect.txt
new file mode 100644
index 000000000000..c62d86e4c52d
--- /dev/null
+++ b/Documentation/devicetree/bindings/interconnect/interconnect.txt
@@ -0,0 +1,91 @@ 
+Interconnect Provider Device Tree Bindings
+=========================================
+
+The purpose of this document is to define a common set of generic interconnect
+providers/consumers properties.
+
+
+= interconnect providers =
+
+The interconnect provider binding is intended to represent the interconnect
+controllers in the system. Each provider registers a set of interconnect
+nodes, which expose the interconnect related capabilities of the interconnect
+to consumer drivers. These capabilities can be throughput, latency, priority
+etc. The consumer drivers set constraints on interconnect path (or endpoints)
+depending on the usecase.
+
+Required properties:
+- compatible : contains the interconnect provider vendor specific compatible
+	       string
+- reg : register space of the interconnect controller hardware
+- #interconnect-cells : number of cells in a interconnect specifier needed to
+		       encode the interconnect node id.
+
+
+Optional properties:
+interconnect-port : A phandle and interconnect provider specifier as defined by
+		bindings of the interconnect provider specified by phandle.
+		This denotes the port to which the interconnect consumer is
+		wired. It is used when there are multiple interconnect providers
+		that have one or multiple links between them.
+
+Example:
+
+		snoc: snoc@0580000 {
+			compatible = "qcom,msm-bus-snoc";
+			reg = <0x580000 0x14000>;
+			#interconnect-cells = <1>;
+			clock-names = "bus_clk", "bus_a_clk";
+			clocks = <&rpmcc RPM_SMD_SNOC_CLK>, <&rpmcc RPM_SMD_SNOC_A_CLK>;
+			status = "okay";
+			interconnect-port = <&bimc MAS_SNOC_CFG>,
+					<&bimc SNOC_BIMC_0_MAS>,
+					<&bimc SNOC_BIMC_1_MAS>,
+					<&pnoc SNOC_PNOC_SLV>;
+		};
+		bimc: bimc@0400000 {
+			compatible = "qcom,msm-bus-bimc";
+			reg = <0x400000 0x62000>;
+			#interconnect-cells = <1>;
+			clock-names = "bus_clk", "bus_a_clk";
+			clocks = <&rpmcc RPM_SMD_BIMC_CLK>, <&rpmcc RPM_SMD_BIMC_A_CLK>;
+			status = "okay";
+			interconnect-port = <&snoc BIMC_SNOC_MAS>;
+		};
+		pnoc: pnoc@500000 {
+			compatible = "qcom,msm-bus-pnoc";
+			reg = <0x500000 0x11000>;
+			#interconnect-cells = <1>;
+			clock-names = "bus_clk", "bus_a_clk";
+			clocks = <&rpmcc RPM_SMD_PCNOC_CLK>, <&rpmcc RPM_SMD_PCNOC_A_CLK>;
+			status = "okay";
+			interconnect-port = <&snoc PNOC_SNOC_SLV>;
+		};
+
+= interconnect consumers =
+
+The interconnect consumers are device nodes which consume the interconnect
+path(s) provided by the interconnect provider. There can be multiple
+interconnect providers on a SoC and the consumer may consume multiple paths
+from different providers depending on usecase and the components it has to
+interact with.
+
+Required-properties:
+interconnect-port : A phandle and interconnect provider specifier as defined by
+		bindings of the interconnect provider specified by phandle.
+		This denotes the port to which the interconnect consumer is
+		wired.
+interconnect-path : List of phandles to the data path endpoints.
+interconnect-path-names : List of interconnect path name strings sorted in the
+		same order as the interconnect-path property.  Consumers drivers
+		will use interconnect-path-names to match the link names with
+		interconnect specifiers.
+
+Example:
+
+	sdhci@07864000 {
+		...
+		interconnect-port = <&pnoc MAS_PNOC_SDCC_2>;
+		interconnect-path = <&blsp1_uart2>;
+		interconnect-path-names = "spi";
+	};
diff --git a/Documentation/interconnect/interconnect.txt b/Documentation/interconnect/interconnect.txt
new file mode 100644
index 000000000000..051d3955f28b
--- /dev/null
+++ b/Documentation/interconnect/interconnect.txt
@@ -0,0 +1,68 @@ 
+GENERIC SYSTEM INTERCONNECT CONTROLLER SUBSYSTEM
+===============================================
+
+1. 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. This can be
+controlled dynamically in order to save power or provide maximum performance.
+
+The interconnect controller 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 controllers are the interconnects between
+various components on chipsets. There can be multiple interconnects on a SoC
+that can be multi-tiered.
+
+Below is a simplified diagram of a real-world SoC topology. The interconnect
+providers are the memory front end and the NoCs.
+
++----------------+    +----------------+
+| HW Accelerator |--->|      M NoC     |<---------------+
++----------------+    +----------------+                |
+                        |      |                    +------------+
+          +-------------+      V       +------+     |            |
+          |                +--------+  | PCIe |     |            |
+          |                | Slaves |  +------+     |            |
+          |                +--------+     |         |   C NoC    |
+          V                               V         |            |
++------------------+   +------------------------+   |            |   +-----+
+|                  |-->|                        |-->|            |-->| CPU |
+|                  |-->|                        |<--|            |   +-----+
+|      Memory      |   |         S NoC          |   +------------+
+|                  |<--|                        |---------+    |
+|                  |<--|                        |<------+ |    |   +--------+
++------------------+   +------------------------+       | |    +-->| Slaves |
+   ^     ^    ^           ^                             | |        +--------+
+   |     |    |           |                             | V
++-----+  |  +-----+    +-----+  +---------+   +----------------+   +--------+
+| CPU |  |  | GPU |    | DSP |  | Masters |-->|       P NoC    |-->| Slaves |
++-----+  |  +-----+    +-----+  +---------+   +----------------+   +--------+
+         |
+     +-------+
+     | Modem |
+     +-------+
+
+2. Interconnect providers
+------------------------
+Interconnect provider is an entity that implements methods to initialize and
+configure a interconnect controller hardware.
+
+An interconnect controller should register with the interconnect provider core
+with interconnect_add_provider().
+
+A previously registered interconnect provider is unregistered with
+interconnect_del_provider().
+
+3. Interconnect consumers
+------------------------
+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.
+
+The interconnect framework provide the following APIs to consumers:
+
+struct interconnect_path *interconnect_get(struct device *dev, const char *id);
+void interconnect_put(struct interconnect_path *path);
+int interconnect_set(interconnect_path *path, u32 bandwidth);
diff --git a/drivers/Kconfig b/drivers/Kconfig
index d2ac339de85f..6e4d80e98f5c 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -198,4 +198,6 @@  source "drivers/hwtracing/intel_th/Kconfig"
 
 source "drivers/fpga/Kconfig"
 
+source "drivers/interconnect/Kconfig"
+
 endmenu
diff --git a/drivers/Makefile b/drivers/Makefile
index 795d0ca714bf..d5b4733f3875 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -172,3 +172,4 @@  obj-$(CONFIG_STM)		+= hwtracing/stm/
 obj-$(CONFIG_ANDROID)		+= android/
 obj-$(CONFIG_NVMEM)		+= nvmem/
 obj-$(CONFIG_FPGA)		+= fpga/
+obj-$(CONFIG_INTERCONNECT)	+= interconnect/
diff --git a/drivers/interconnect/Kconfig b/drivers/interconnect/Kconfig
new file mode 100644
index 000000000000..103524b59905
--- /dev/null
+++ b/drivers/interconnect/Kconfig
@@ -0,0 +1,10 @@ 
+menuconfig INTERCONNECT
+	bool "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..184da73ce0d2
--- /dev/null
+++ b/drivers/interconnect/Makefile
@@ -0,0 +1 @@ 
+obj-y  += interconnect.o
diff --git a/drivers/interconnect/interconnect.c b/drivers/interconnect/interconnect.c
new file mode 100644
index 000000000000..dadd1ffdbc50
--- /dev/null
+++ b/drivers/interconnect/interconnect.c
@@ -0,0 +1,285 @@ 
+/*
+ * Copyright (c) 2017, Linaro Ltd.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/device.h>
+#include <linux/init.h>
+#include <linux/list.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/interconnect-consumer.h>
+#include <linux/interconnect-provider.h>
+#include <linux/property.h>
+#include <linux/slab.h>
+
+static DEFINE_MUTEX(interconnect_provider_list_mutex);
+static LIST_HEAD(interconnect_provider_list);
+
+static struct interconnect_node *find_node(struct device_node *np)
+{
+	struct interconnect_node *node = ERR_PTR(-EPROBE_DEFER);
+	int ret;
+	struct of_phandle_args args;
+	struct icp *i, *icp = NULL;
+
+	/* find the target interconnect provider device_node */
+	ret = of_parse_phandle_with_args(np, "interconnect-port",
+					 "#interconnect-cells", 0, &args);
+	if (ret) {
+		pr_err("%s interconnect provider not found (%d)\n", __func__,
+		       ret);
+		return ERR_PTR(ret);
+	}
+
+	mutex_lock(&interconnect_provider_list_mutex);
+
+	/* find the interconnect provider of the target node */
+	list_for_each_entry(i, &interconnect_provider_list, icp_list) {
+		if (args.np == i->of_node) {
+			icp = i;
+			node = icp->ops->xlate(&args, icp->data);
+			break;
+		}
+	}
+
+	mutex_unlock(&interconnect_provider_list_mutex);
+
+	of_node_put(args.np);
+
+	if (!icp) {
+		pr_err("%s interconnect provider %s not found\n", __func__,
+		       args.np->name);
+		return ERR_PTR(-EPROBE_DEFER);
+	}
+
+	if (IS_ERR(node)) {
+		pr_err("%s interconnect node %s not found (%ld)\n", __func__,
+		       args.np->name, PTR_ERR(node));
+		return node;
+	}
+
+	return node;
+}
+
+static int find_path(struct interconnect_node *src,
+		     struct interconnect_node *dst,
+		     struct interconnect_path *path)
+{
+	struct list_head edge_list;
+	struct list_head traverse_list;
+	struct interconnect_path *tmp_path;
+	struct interconnect_node *node = NULL;
+	size_t i;
+	bool found = false;
+
+	INIT_LIST_HEAD(&traverse_list);
+	INIT_LIST_HEAD(&edge_list);
+
+	tmp_path = kzalloc(sizeof(*tmp_path), GFP_KERNEL);
+	if (!tmp_path)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&tmp_path->node_list);
+
+	list_add_tail(&src->search_list, &traverse_list);
+
+	do {
+		list_for_each_entry(node, &traverse_list, search_list) {
+			if (node == dst) {
+				found = true;
+				list_add(&node->search_list,
+					 &tmp_path->node_list);
+				break;
+			}
+			for (i = 0; i < node->num_links; i++) {
+				struct interconnect_node *tmp = node->links[i];
+
+				/* try DT lookup */
+				if (!tmp) {
+					tmp = find_node(node->icp->of_node);
+					if (IS_ERR(tmp))
+						return PTR_ERR(tmp);
+				}
+
+				if (tmp->is_traversed)
+					continue;
+
+				tmp->is_traversed = true;
+				tmp->reverse = node;
+				list_add_tail(&tmp->search_list, &edge_list);
+			}
+		}
+		if (found)
+			break;
+
+		list_splice_init(&traverse_list, &tmp_path->node_list);
+		list_splice_init(&edge_list, &traverse_list);
+
+	} while (!list_empty(&traverse_list));
+
+	/* reset the is_traversed state */
+	list_for_each_entry(node, &path->node_list, search_list) {
+		node->is_traversed = false;
+	}
+
+	/* add the path */
+	node = list_first_entry(&tmp_path->node_list, struct interconnect_node,
+				search_list);
+	while (node) {
+		list_add_tail(&node->search_list, &path->node_list);
+		node = node->reverse;
+	}
+
+	kfree(tmp_path);
+
+	return 0;
+}
+
+int interconnect_set(struct interconnect_path *path, u32 bandwidth)
+{
+	struct interconnect_node *node;
+
+	list_for_each_entry(node, &path->node_list, search_list) {
+		if (node->icp->ops->set)
+			node->icp->ops->set(node, bandwidth);
+	}
+
+	return 0;
+}
+
+struct interconnect_path *interconnect_get(struct device *dev, const char *id)
+{
+	struct device_node *np;
+	struct platform_device *dst_pdev;
+	struct interconnect_node *src, *dst, *node;
+	struct interconnect_path *path;
+	int ret, index;
+
+	if (WARN_ON(!dev || !id))
+		return ERR_PTR(-EINVAL);
+
+	src = find_node(dev->of_node);
+	if (IS_ERR(src))
+		return ERR_CAST(src);
+
+	index = of_property_match_string(dev->of_node,
+					 "interconnect-path-names", id);
+	if (index < 0) {
+		dev_err(dev, "missing interconnect-path-names DT property on %s\n",
+			dev->of_node->full_name);
+		return ERR_PTR(index);
+	}
+
+	/* get the destination endpoint device_node */
+	np = of_parse_phandle(dev->of_node, "interconnect-path", index);
+
+	dst_pdev = of_find_device_by_node(np);
+	if (!dst_pdev) {
+		dev_err(dev, "error finding device by node %s\n", np->name);
+		return ERR_PTR(-ENODEV);
+	}
+
+	dst = find_node(np);
+	if (IS_ERR(dst))
+		return ERR_CAST(dst);
+
+	/* find a path between the source and destination */
+	path = kzalloc(sizeof(*path), GFP_KERNEL);
+	if (!path)
+		return ERR_PTR(-ENOMEM);
+
+	INIT_LIST_HEAD(&path->node_list);
+	path->src_dev = dev;
+	path->dst_dev = &dst_pdev->dev;
+
+	/* TODO: cache the path */
+	ret = find_path(src, dst, path);
+	if (ret) {
+		dev_err(dev, "error finding path between %p and %p (%d)\n",
+			src, dst, ret);
+		return ERR_PTR(-EINVAL);
+	}
+
+	list_for_each_entry(node, &path->node_list, search_list) {
+		struct icn_qos *req;
+
+		/*
+		 * Create icn_qos for each separate link between the nodes.
+		 * They may have different constraints and may belong to
+		 * different interconnect providers.
+		 */
+		req = kzalloc(sizeof(*req), GFP_KERNEL);
+		if (!req)
+			return ERR_PTR(-ENOMEM);
+
+		req->path = path;
+		req->bandwidth = 0;
+		hlist_add_head(&req->node, &node->qos_list);
+	}
+
+	return path;
+}
+EXPORT_SYMBOL_GPL(interconnect_get);
+
+void interconnect_put(struct interconnect_path *path)
+{
+	struct interconnect_node *node;
+	struct icn_qos *req;
+	struct hlist_node *tmp;
+
+	if (IS_ERR(path))
+		return;
+
+	list_for_each_entry(node, &path->node_list, search_list) {
+		hlist_for_each_entry_safe(req, tmp, &node->qos_list, node) {
+			if (req->path == path) {
+				hlist_del(&req->node);
+				kfree(req);
+			}
+		}
+	}
+
+	kfree(path);
+}
+EXPORT_SYMBOL_GPL(interconnect_put);
+
+int interconnect_add_provider(struct icp *icp)
+{
+	struct interconnect_node *node;
+
+	WARN(!icp->ops->xlate, "%s: .xlate is not implemented\n", __func__);
+	WARN(!icp->ops->set, "%s: .set is not implemented\n", __func__);
+
+	mutex_lock(&interconnect_provider_list_mutex);
+	list_add(&icp->icp_list, &interconnect_provider_list);
+	mutex_unlock(&interconnect_provider_list_mutex);
+
+	list_for_each_entry(node, &icp->nodes, icn_list) {
+		INIT_HLIST_HEAD(&node->qos_list);
+	}
+
+	dev_info(icp->dev, "added interconnect provider %s\n", icp->name);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(interconnect_add_provider);
+
+int interconnect_del_provider(struct icp *icp)
+{
+	mutex_lock(&interconnect_provider_list_mutex);
+	of_node_put(icp->of_node);
+	list_del(&icp->icp_list);
+	mutex_unlock(&interconnect_provider_list_mutex);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(interconnect_del_provider);
diff --git a/include/linux/interconnect-consumer.h b/include/linux/interconnect-consumer.h
new file mode 100644
index 000000000000..8bd5bb3e4196
--- /dev/null
+++ b/include/linux/interconnect-consumer.h
@@ -0,0 +1,70 @@ 
+/*
+ * Copyright (c) 2017, Linaro Ltd.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef _LINUX_INTERCONNECT_CONSUMER_H
+#define _LINUX_INTERCONNECT_CONSUMER_H
+
+struct interconnect_node;
+
+/**
+ * struct interconnect_path - interconnect path structure
+ *
+ * @node_list: list of the interconnect nodes
+ * @src_dev: source endpoint
+ * @dst_dev: destination endpoint
+ */
+struct interconnect_path {
+	struct list_head node_list;
+	struct device *src_dev;
+	struct device *dst_dev;
+};
+
+/**
+ * interconnect_get() - get an interconnect path from a given id
+ *
+ * @dev: the source device which will set constraints on the path
+ * @id: endpoint node string identifier
+ *
+ * This function will search for a path between the source device (caller)
+ * and a destination endpoint. It returns an interconnect_path handle on
+ * success. Use interconnect_put() to release constraints when the they
+ * are not needed anymore.
+ *
+ * This function returns a handle on success, or ERR_PTR() otherwise.
+ */
+struct interconnect_path *interconnect_get(struct device *dev, const char *id);
+
+/**
+ * interconnect_put() - release the reference to the interconnect path
+ *
+ * @path: interconnect path
+ *
+ * Use this function to release the path and free the memory when setting
+ * constraints on the path is no longer needed.
+ */
+void interconnect_put(struct interconnect_path *path);
+
+/**
+ * interconnect_set() - set constraints on a path between two endpoints
+ * @path: reference to the path returned by interconnect_get()
+ * @bandwidth: the requested bandwidth in kpbs between the path endpoints
+ *
+ * This function sends a request for bandwidth between the two endpoints,
+ * (path). It aggragates the requests for constraints and updates each node
+ * accordingly.
+ *
+ * Returns 0 on success, or an approproate error code otherwise.
+ */
+int interconnect_set(struct interconnect_path *path, u32 bandwidth);
+
+#endif /* _LINUX_INTERCONNECT_CONSUMER_H */
diff --git a/include/linux/interconnect-provider.h b/include/linux/interconnect-provider.h
new file mode 100644
index 000000000000..af1ca739ce52
--- /dev/null
+++ b/include/linux/interconnect-provider.h
@@ -0,0 +1,92 @@ 
+/*
+ * Copyright (c) 2017, Linaro Ltd.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef _LINUX_INTERCONNECT_PROVIDER_H
+#define _LINUX_INTERCONNECT_PROVIDER_H
+
+#include <linux/interconnect-consumer.h>
+
+/**
+ * struct icp_ops - platform specific callback operations for interconnect
+ * providers that will be called from drivers
+ *
+ * @set: set constraints on interconnect
+ * @xlate: provider-specific callback for mapping nodes from phandle arguments
+ */
+struct icp_ops {
+	int (*set)(struct interconnect_node *node, u32 bandwidth);
+	struct interconnect_node *(*xlate)(struct of_phandle_args *spec, void *data);
+};
+
+/**
+ * struct icp - interconnect provider (controller) entity that might
+ * provide multiple interconnect controls
+ *
+ * @icp_list: list of the registered interconnect providers
+ * @nodes: internal list of the interconnect provider nodes
+ * @ops: pointer to device specific struct icp_ops
+ * @dev: the device this interconnect provider belongs to
+ * @of_node: the corresponding device tree node as phandle target
+ * @data: pointer to private data
+ */
+struct icp {
+	struct list_head	icp_list;
+	struct list_head	nodes;
+	const struct icp_ops	*ops;
+	struct device		*dev;
+	const char		*name;
+	struct device_node	*of_node;
+	void			*data;
+};
+
+/**
+ * struct interconnect_node - entity that is part of the interconnect topology
+ *
+ * @links: links to other interconnect nodes
+ * @num_links: number of interconnect nodes
+ * @icp: points to the interconnect provider struct this node belongs to
+ * @icn_list: list of interconnect nodes
+ * @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
+ * @qos_list: a list of QoS constraints
+ */
+struct interconnect_node {
+	struct interconnect_node **links;
+	size_t			num_links;
+
+	struct icp		*icp;
+	struct list_head	icn_list;
+	struct list_head	search_list;
+	struct interconnect_node *reverse;
+	bool			is_traversed;
+	struct hlist_head	qos_list;
+};
+
+/**
+ * struct icn_qos - constraints that are attached to each node
+ *
+ * @node: linked list node
+ * @path: the interconnect path which is using this constraint
+ * @bandwidth: an integer describing the bandwidth in kbps
+ */
+struct icn_qos {
+	struct hlist_node node;
+	struct interconnect_path *path;
+	u32 bandwidth;
+};
+
+int interconnect_add_provider(struct icp *icp);
+int interconnect_del_provider(struct icp *icp);
+
+#endif /* _LINUX_INTERCONNECT_PROVIDER_H */