interconnect: Allow endpoints translation via DT

This change “interconnect: Allow endpoints translation via DT” in Linux kernel is authored by Georgi Djakov <georgi.djakov [at] linaro.org> on Wed Jan 16 18:10:58 2019 +0200.

interconnect: Allow endpoints translation via DT

Currently we support only platform data for specifying the interconnect
endpoints. As now the endpoints are hard-coded into the consumer driver
this may lead to complications when a single driver is used by multiple
SoCs, which may have different interconnect topology.
To avoid cluttering the consumer drivers, introduce a translation function
to help us get the board specific interconnect data from device-tree.

Reviewed-by: Evan Green <evgreen@chromium.org>
Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This Linux change may have been applied to various maintained Linux releases and you can find Linux releases including commit 87e3031.

There are 173 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 drivers/interconnect/core.c           | 149 ++++++++++++++++++++++++++++++++++
 include/linux/interconnect-provider.h |  17 ++++
 include/linux/interconnect.h          |   7 ++
 3 files changed, 173 insertions(+)

diff --git a/drivers/interconnect/core.c b/drivers/interconnect/core.c
index 2b937b4..a8c2bd3 100644
--- a/drivers/interconnect/core.c
+++ b/drivers/interconnect/core.c
@@ -15,6 +15,7 @@
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/slab.h>
+#include <linux/of.h>
 #include <linux/overflow.h>
 
 static DEFINE_IDR(icc_idr);
@@ -194,6 +195,152 @@ static int apply_constraints(struct icc_path *path)
 	return ret;
 }
 
+/* of_icc_xlate_onecell() - Translate function using a single index.
+ * @spec: OF phandle args to map into an interconnect node.
+ * @data: private data (pointer to struct icc_onecell_data)
+ *
+ * This is a generic translate function that can be used to model simple
+ * interconnect providers that have one device tree node and provide
+ * multiple interconnect nodes. A single cell is used as an index into
+ * an array of icc nodes specified in the icc_onecell_data struct when
+ * registering the provider.
+ */
+struct icc_node *of_icc_xlate_onecell(struct of_phandle_args *spec,
+				      void *data)
+{
+	struct icc_onecell_data *icc_data = data;
+	unsigned int idx = spec->args[0];
+
+	if (idx >= icc_data->num_nodes) {
+		pr_err("%s: invalid index %un", __func__, idx);
+		return ERR_PTR(-EINVAL);
+	}
+
+	return icc_data->nodes[idx];
+}
+EXPORT_SYMBOL_GPL(of_icc_xlate_onecell);
+
+/**
+ * of_icc_get_from_provider() - Look-up interconnect node
+ * @spec: OF phandle args to use for look-up
+ *
+ * Looks for interconnect provider under the node specified by @spec and if
+ * found, uses xlate function of the provider to map phandle args to node.
+ *
+ * Returns a valid pointer to struct icc_node on success or ERR_PTR()
+ * on failure.
+ */
+static struct icc_node *of_icc_get_from_provider(struct of_phandle_args *spec)
+{
+	struct icc_node *node = ERR_PTR(-EPROBE_DEFER);
+	struct icc_provider *provider;
+
+	if (!spec || spec->args_count != 1)
+		return ERR_PTR(-EINVAL);
+
+	mutex_lock(&icc_lock);
+	list_for_each_entry(provider, &icc_providers, provider_list) {
+		if (provider->dev->of_node == spec->np)
+			node = provider->xlate(spec, provider->data);
+		if (!IS_ERR(node))
+			break;
+	}
+	mutex_unlock(&icc_lock);
+
+	return node;
+}
+
+/**
+ * of_icc_get() - get a path handle from a DT node based on name
+ * @dev: device pointer for the consumer device
+ * @name: interconnect path name
+ *
+ * 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 they
+ * are not needed anymore.
+ * If the interconnect API is disabled, NULL is returned and the consumer
+ * drivers will still build. Drivers are free to handle this specifically,
+ * but they don't have to.
+ *
+ * Return: icc_path pointer on success or ERR_PTR() on error. NULL is returned
+ * when the API is disabled or the "interconnects" DT property is missing.
+ */
+struct icc_path *of_icc_get(struct device *dev, const char *name)
+{
+	struct icc_path *path = ERR_PTR(-EPROBE_DEFER);
+	struct icc_node *src_node, *dst_node;
+	struct device_node *np = NULL;
+	struct of_phandle_args src_args, dst_args;
+	int idx = 0;
+	int ret;
+
+	if (!dev || !dev->of_node)
+		return ERR_PTR(-ENODEV);
+
+	np = dev->of_node;
+
+	/*
+	 * When the consumer DT node do not have "interconnects" property
+	 * return a NULL path to skip setting constraints.
+	 */
+	if (!of_find_property(np, "interconnects", NULL))
+		return NULL;
+
+	/*
+	 * We use a combination of phandle and specifier for endpoint. For now
+	 * lets support only global ids and extend this in the future if needed
+	 * without breaking DT compatibility.
+	 */
+	if (name) {
+		idx = of_property_match_string(np, "interconnect-names", name);
+		if (idx < 0)
+			return ERR_PTR(idx);
+	}
+
+	ret = of_parse_phandle_with_args(np, "interconnects",
+					 "#interconnect-cells", idx * 2,
+					 &src_args);
+	if (ret)
+		return ERR_PTR(ret);
+
+	of_node_put(src_args.np);
+
+	ret = of_parse_phandle_with_args(np, "interconnects",
+					 "#interconnect-cells", idx * 2 + 1,
+					 &dst_args);
+	if (ret)
+		return ERR_PTR(ret);
+
+	of_node_put(dst_args.np);
+
+	src_node = of_icc_get_from_provider(&src_args);
+
+	if (IS_ERR(src_node)) {
+		if (PTR_ERR(src_node) != -EPROBE_DEFER)
+			dev_err(dev, "error finding src node: %ldn",
+				PTR_ERR(src_node));
+		return ERR_CAST(src_node);
+	}
+
+	dst_node = of_icc_get_from_provider(&dst_args);
+
+	if (IS_ERR(dst_node)) {
+		if (PTR_ERR(dst_node) != -EPROBE_DEFER)
+			dev_err(dev, "error finding dst node: %ldn",
+				PTR_ERR(dst_node));
+		return ERR_CAST(dst_node);
+	}
+
+	mutex_lock(&icc_lock);
+	path = path_find(dev, src_node, dst_node);
+	if (IS_ERR(path))
+		dev_err(dev, "%s: invalid path=%ldn", __func__, PTR_ERR(path));
+	mutex_unlock(&icc_lock);
+
+	return path;
+}
+EXPORT_SYMBOL_GPL(of_icc_get);
+
 /**
  * icc_set_bw() - set bandwidth constraints on an interconnect path
  * @path: reference to the path returned by icc_get()
@@ -519,6 +666,8 @@ int icc_provider_add(struct icc_provider *provider)
 {
 	if (WARN_ON(!provider->set))
 		return -EINVAL;
+	if (WARN_ON(!provider->xlate))
+		return -EINVAL;
 
 	mutex_lock(&icc_lock);
 
diff --git a/include/linux/interconnect-provider.h b/include/linux/interconnect-provider.h
index 78208a7..63cacca 100644
--- a/include/linux/interconnect-provider.h
+++ b/include/linux/interconnect-provider.h
@@ -12,6 +12,21 @@
 #define icc_units_to_bps(bw)  ((bw) * 1000ULL)
 
 struct icc_node;
+struct of_phandle_args;
+
+/**
+ * struct icc_onecell_data - driver data for onecell interconnect providers
+ *
+ * @num_nodes: number of nodes in this device
+ * @nodes: array of pointers to the nodes in this device
+ */
+struct icc_onecell_data {
+	unsigned int num_nodes;
+	struct icc_node *nodes[];
+};
+
+struct icc_node *of_icc_xlate_onecell(struct of_phandle_args *spec,
+				      void *data);
 
 /**
  * struct icc_provider - interconnect provider (controller) entity that might
@@ -21,6 +36,7 @@
  * @nodes: internal list of the interconnect provider nodes
  * @set: pointer to device specific set operation function
  * @aggregate: pointer to device specific aggregate operation function
+ * @xlate: provider-specific callback for mapping nodes from phandle arguments
  * @dev: the device this interconnect provider belongs to
  * @users: count of active users
  * @data: pointer to private data
@@ -31,6 +47,7 @@ struct icc_provider {
 	int (*set)(struct icc_node *src, struct icc_node *dst);
 	int (*aggregate)(struct icc_node *node, u32 avg_bw, u32 peak_bw,
 			 u32 *agg_avg, u32 *agg_peak);
+	struct icc_node* (*xlate)(struct of_phandle_args *spec, void *data);
 	struct device		*dev;
 	int			users;
 	void			*data;
diff --git a/include/linux/interconnect.h b/include/linux/interconnect.h
index c331afb..dc25864 100644
--- a/include/linux/interconnect.h
+++ b/include/linux/interconnect.h
@@ -27,6 +27,7 @@
 
 struct icc_path *icc_get(struct device *dev, const int src_id,
 			 const int dst_id);
+struct icc_path *of_icc_get(struct device *dev, const char *name);
 void icc_put(struct icc_path *path);
 int icc_set_bw(struct icc_path *path, u32 avg_bw, u32 peak_bw);
 
@@ -38,6 +39,12 @@ static inline struct icc_path *icc_get(struct device *dev, const int src_id,
 	return NULL;
 }
 
+static inline struct icc_path *of_icc_get(struct device *dev,
+					  const char *name)
+{
+	return NULL;
+}
+
 static inline void icc_put(struct icc_path *path)
 {
 }

The commit for this change in Linux stable tree is 87e3031 (patch).

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