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 40e575b1d0b3 ("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 <[e-mail]>
Signed-off-by: Suman Anna <[e-mail]>
[fix order of Signed-off-by tags]
Signed-off-by: Ohad Ben-Cohen <[e-mail]>

Documentation/remoteproc.txt

···
         rproc_shutdown() returns, and users can still use it with a subsequent
         rproc_boot(), if needed.
 
+  struct rproc *rproc_get_by_phandle(phandle phandle)
+    - Find an rproc handle using a device tree phandle. Returns the rproc
+      handle on success, and NULL on failure. This function increments
+      the remote processor's refcount, so always use rproc_put() to
+      decrement it back once rproc isn't needed anymore.
+
 3. Typical usage
 
 #include <linux/remoteproc.h>

drivers/remoteproc/remoteproc_core.c

···
 
 #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,
···
 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
  *
···
 	ret = device_add(dev);
 	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);
 
···
 
 	/* 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);
 

include/linux/remoteproc.h

···
 #define REMOTEPROC_H
 
 #include <linux/types.h>
-#include <linux/klist.h>
 #include <linux/mutex.h>
 #include <linux/virtio.h>
 #include <linux/completion.h>
 #include <linux/idr.h>
+#include <linux/of.h>
 
 /**
  * struct resource_table - firmware resource table header
···
 
 /**
  * struct rproc - represents a physical remote processor device
- * @node: klist node of this rproc object
+ * @node: list node of this rproc object
  * @domain: iommu domain
  * @name: human readable name of the rproc
  * @firmware: name of firmware file to be loaded
···
  * @has_iommu: flag to indicate if remote processor is behind an MMU
  */
 struct rproc {
-	struct klist_node node;
+	struct list_head node;
 	struct iommu_domain *domain;
 	const char *name;
 	const char *firmware;
···
 	u32 rsc_offset;
 };
 
+struct rproc *rproc_get_by_phandle(phandle phandle);
 struct rproc *rproc_alloc(struct device *dev, const char *name,
 				const struct rproc_ops *ops,
 				const char *firmware, int len);