PM: wakeup: Add routine to help fetch wakeup source object.

Some user might want to go through all registered wakeup sources
and doing things accordingly. For example, SoC PM driver might need to
do HW programming to prevent powering down specific IP which wakeup
source depending on. So add this API to help walk through all registered
wakeup source objects on that list and return them one by one.
Signed-off-by: Ran Wang <ran.wang_1@nxp.com>
Tested-by: Leonard Crestez <leonard.crestez@nxp.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Li Yang <leoyang.li@nxp.com>

drivers/base/power/wakeup.c

@@ -247,6 +247,60 @@ void wakeup_source_unregister(struct wakeup_source *ws)
 }
 EXPORT_SYMBOL_GPL(wakeup_source_unregister);
 
+/**
+ * wakeup_sources_read_lock - Lock wakeup source list for read.
+ *
+ * Returns an index of srcu lock for struct wakeup_srcu.
+ * This index must be passed to the matching wakeup_sources_read_unlock().
+ */
+int wakeup_sources_read_lock(void)
+{
+	return srcu_read_lock(&wakeup_srcu);
+}
+EXPORT_SYMBOL_GPL(wakeup_sources_read_lock);
+
+/**
+ * wakeup_sources_read_unlock - Unlock wakeup source list.
+ * @idx: return value from corresponding wakeup_sources_read_lock()
+ */
+void wakeup_sources_read_unlock(int idx)
+{
+	srcu_read_unlock(&wakeup_srcu, idx);
+}
+EXPORT_SYMBOL_GPL(wakeup_sources_read_unlock);
+
+/**
+ * wakeup_sources_walk_start - Begin a walk on wakeup source list
+ *
+ * Returns first object of the list of wakeup sources.
+ *
+ * Note that to be safe, wakeup sources list needs to be locked by calling
+ * wakeup_source_read_lock() for this.
+ */
+struct wakeup_source *wakeup_sources_walk_start(void)
+{
+	struct list_head *ws_head = &wakeup_sources;
+
+	return list_entry_rcu(ws_head->next, struct wakeup_source, entry);
+}
+EXPORT_SYMBOL_GPL(wakeup_sources_walk_start);
+
+/**
+ * wakeup_sources_walk_next - Get next wakeup source from the list
+ * @ws: Previous wakeup source object
+ *
+ * Note that to be safe, wakeup sources list needs to be locked by calling
+ * wakeup_source_read_lock() for this.
+ */
+struct wakeup_source *wakeup_sources_walk_next(struct wakeup_source *ws)
+{
+	struct list_head *ws_head = &wakeup_sources;
+
+	return list_next_or_null_rcu(ws_head, &ws->entry,
+				struct wakeup_source, entry);
+}
+EXPORT_SYMBOL_GPL(wakeup_sources_walk_next);
+
 /**
  * device_wakeup_attach - Attach a wakeup source object to a device object.
  * @dev: Device to handle.

include/linux/pm_wakeup.h

@@ -63,6 +63,11 @@ struct wakeup_source {
 	bool			autosleep_enabled:1;
 };
 
+#define for_each_wakeup_source(ws) \
+	for ((ws) = wakeup_sources_walk_start();	\
+	     (ws);					\
+	     (ws) = wakeup_sources_walk_next((ws)))
+
 #ifdef CONFIG_PM_SLEEP
 
 /*
@@ -92,6 +97,10 @@ extern void wakeup_source_remove(struct wakeup_source *ws);
 extern struct wakeup_source *wakeup_source_register(struct device *dev,
 						    const char *name);
 extern void wakeup_source_unregister(struct wakeup_source *ws);
+extern int wakeup_sources_read_lock(void);
+extern void wakeup_sources_read_unlock(int idx);
+extern struct wakeup_source *wakeup_sources_walk_start(void);
+extern struct wakeup_source *wakeup_sources_walk_next(struct wakeup_source *ws);
 extern int device_wakeup_enable(struct device *dev);
 extern int device_wakeup_disable(struct device *dev);
 extern void device_set_wakeup_capable(struct device *dev, bool capable);