remoteproc: introduce rproc_get_by_phandle API

Allow users of remoteproc the ability to get a handle to an rproc by
passing a phandle supplied in the user's device tree node. This is
useful in situations that require manual booting of the rproc.

This patch uses the code removed by commit 40e575b1d0 ("remoteproc:
remove the get_by_name/put API") for the ref counting but is modified
to use a simple list and locking mechanism and has rproc_get_by_name
replaced with an rproc_get_by_phandle API.

Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
Signed-off-by: Suman Anna <s-anna@ti.com>
[fix order of Signed-off-by tags]
Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>

drivers/remoteproc/remoteproc_core.c

@@ -44,6 +44,9 @@
 
 #include "remoteproc_internal.h"
 
+static DEFINE_MUTEX(rproc_list_mutex);
+static LIST_HEAD(rproc_list);
+
 typedef int (*rproc_handle_resources_t)(struct rproc *rproc,
 				struct resource_table *table, int len);
 typedef int (*rproc_handle_resource_t)(struct rproc *rproc,
@@ -1144,6 +1147,43 @@ out:
 }
 EXPORT_SYMBOL(rproc_shutdown);
 
+/**
+ * rproc_get_by_phandle() - find a remote processor by phandle
+ * @phandle: phandle to the rproc
+ *
+ * Finds an rproc handle using the remote processor's phandle, and then
+ * return a handle to the rproc.
+ *
+ * This function increments the remote processor's refcount, so always
+ * use rproc_put() to decrement it back once rproc isn't needed anymore.
+ *
+ * Returns the rproc handle on success, and NULL on failure.
+ */
+struct rproc *rproc_get_by_phandle(phandle phandle)
+{
+	struct rproc *rproc = NULL, *r;
+	struct device_node *np;
+
+	np = of_find_node_by_phandle(phandle);
+	if (!np)
+		return NULL;
+
+	mutex_lock(&rproc_list_mutex);
+	list_for_each_entry(r, &rproc_list, node) {
+		if (r->dev.parent && r->dev.parent->of_node == np) {
+			rproc = r;
+			get_device(&rproc->dev);
+			break;
+		}
+	}
+	mutex_unlock(&rproc_list_mutex);
+
+	of_node_put(np);
+
+	return rproc;
+}
+EXPORT_SYMBOL(rproc_get_by_phandle);
+
 /**
  * rproc_add() - register a remote processor
  * @rproc: the remote processor handle to register
@@ -1173,6 +1213,11 @@ int rproc_add(struct rproc *rproc)
 	if (ret < 0)
 		return ret;
 
+	/* expose to rproc_get_by_phandle users */
+	mutex_lock(&rproc_list_mutex);
+	list_add(&rproc->node, &rproc_list);
+	mutex_unlock(&rproc_list_mutex);
+
 	dev_info(dev, "%s is available\n", rproc->name);
 
 	dev_info(dev, "Note: remoteproc is still under development and considered experimental.\n");
@@ -1360,6 +1405,11 @@ int rproc_del(struct rproc *rproc)
 	/* Free the copy of the resource table */
 	kfree(rproc->cached_table);
 
+	/* the rproc is downref'ed as soon as it's removed from the klist */
+	mutex_lock(&rproc_list_mutex);
+	list_del(&rproc->node);
+	mutex_unlock(&rproc_list_mutex);
+
 	device_del(&rproc->dev);
 
 	return 0;