1 files changed, 125 insertions, 32 deletions

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 62572d59e..a0927c7f8 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -37,7 +37,11 @@ static HLIST_HEAD(clk_root_list);
 static HLIST_HEAD(clk_orphan_list);
 static LIST_HEAD(clk_notifier_list);
 
-static struct hlist_head *all_lists[] = {
+/* List of registered clks that use runtime PM */
+static HLIST_HEAD(clk_rpm_list);
+static DEFINE_MUTEX(clk_rpm_list_lock);
+
+static const struct hlist_head *all_lists[] = {
 	&clk_root_list,
 	&clk_orphan_list,
 	NULL,
@@ -59,6 +63,7 @@ struct clk_core {
 	struct clk_hw		*hw;
 	struct module		*owner;
 	struct device		*dev;
+	struct hlist_node	rpm_node;
 	struct device_node	*of_node;
 	struct clk_core		*parent;
 	struct clk_parent_map	*parents;
@@ -129,6 +134,89 @@ static void clk_pm_runtime_put(struct clk_core *core)
 	pm_runtime_put_sync(core->dev);
 }
 
+/**
+ * clk_pm_runtime_get_all() - Runtime "get" all clk provider devices
+ *
+ * Call clk_pm_runtime_get() on all runtime PM enabled clks in the clk tree so
+ * that disabling unused clks avoids a deadlock where a device is runtime PM
+ * resuming/suspending and the runtime PM callback is trying to grab the
+ * prepare_lock for something like clk_prepare_enable() while
+ * clk_disable_unused_subtree() holds the prepare_lock and is trying to runtime
+ * PM resume/suspend the device as well.
+ *
+ * Context: Acquires the 'clk_rpm_list_lock' and returns with the lock held on
+ * success. Otherwise the lock is released on failure.
+ *
+ * Return: 0 on success, negative errno otherwise.
+ */
+static int clk_pm_runtime_get_all(void)
+{
+	int ret;
+	struct clk_core *core, *failed;
+
+	/*
+	 * Grab the list lock to prevent any new clks from being registered
+	 * or unregistered until clk_pm_runtime_put_all().
+	 */
+	mutex_lock(&clk_rpm_list_lock);
+
+	/*
+	 * Runtime PM "get" all the devices that are needed for the clks
+	 * currently registered. Do this without holding the prepare_lock, to
+	 * avoid the deadlock.
+	 */
+	hlist_for_each_entry(core, &clk_rpm_list, rpm_node) {
+		ret = clk_pm_runtime_get(core);
+		if (ret) {
+			failed = core;
+			pr_err("clk: Failed to runtime PM get '%s' for clk '%s'\n",
+			       dev_name(failed->dev), failed->name);
+			goto err;
+		}
+	}
+
+	return 0;
+
+err:
+	hlist_for_each_entry(core, &clk_rpm_list, rpm_node) {
+		if (core == failed)
+			break;
+
+		clk_pm_runtime_put(core);
+	}
+	mutex_unlock(&clk_rpm_list_lock);
+
+	return ret;
+}
+
+/**
+ * clk_pm_runtime_put_all() - Runtime "put" all clk provider devices
+ *
+ * Put the runtime PM references taken in clk_pm_runtime_get_all() and release
+ * the 'clk_rpm_list_lock'.
+ */
+static void clk_pm_runtime_put_all(void)
+{
+	struct clk_core *core;
+
+	hlist_for_each_entry(core, &clk_rpm_list, rpm_node)
+		clk_pm_runtime_put(core);
+	mutex_unlock(&clk_rpm_list_lock);
+}
+
+static void clk_pm_runtime_init(struct clk_core *core)
+{
+	struct device *dev = core->dev;
+
+	if (dev && pm_runtime_enabled(dev)) {
+		core->rpm_enabled = true;
+
+		mutex_lock(&clk_rpm_list_lock);
+		hlist_add_head(&core->rpm_node, &clk_rpm_list);
+		mutex_unlock(&clk_rpm_list_lock);
+	}
+}
+
 /***           locking             ***/
 static void clk_prepare_lock(void)
 {
@@ -425,6 +513,9 @@ static struct clk_core *clk_core_get(struct clk_core *core, u8 p_index)
 	if (IS_ERR(hw))
 		return ERR_CAST(hw);
 
+	if (!hw)
+		return NULL;
+
 	return hw->core;
 }
 
@@ -1228,9 +1319,6 @@ static void __init clk_unprepare_unused_subtree(struct clk_core *core)
 	if (core->flags & CLK_IGNORE_UNUSED)
 		return;
 
-	if (clk_pm_runtime_get(core))
-		return;
-
 	if (clk_core_is_prepared(core)) {
 		trace_clk_unprepare(core);
 		if (core->ops->unprepare_unused)
@@ -1239,8 +1327,6 @@ static void __init clk_unprepare_unused_subtree(struct clk_core *core)
 			core->ops->unprepare(core->hw);
 		trace_clk_unprepare_complete(core);
 	}
-
-	clk_pm_runtime_put(core);
 }
 
 static void __init clk_disable_unused_subtree(struct clk_core *core)
@@ -1256,9 +1342,6 @@ static void __init clk_disable_unused_subtree(struct clk_core *core)
 	if (core->flags & CLK_OPS_PARENT_ENABLE)
 		clk_core_prepare_enable(core->parent);
 
-	if (clk_pm_runtime_get(core))
-		goto unprepare_out;
-
 	flags = clk_enable_lock();
 
 	if (core->enable_count)
@@ -1283,8 +1366,6 @@ static void __init clk_disable_unused_subtree(struct clk_core *core)
 
 unlock_out:
 	clk_enable_unlock(flags);
-	clk_pm_runtime_put(core);
-unprepare_out:
 	if (core->flags & CLK_OPS_PARENT_ENABLE)
 		clk_core_disable_unprepare(core->parent);
 }
@@ -1300,12 +1381,22 @@ __setup("clk_ignore_unused", clk_ignore_unused_setup);
 static int __init clk_disable_unused(void)
 {
 	struct clk_core *core;
+	int ret;
 
 	if (clk_ignore_unused) {
 		pr_warn("clk: Not disabling unused clocks\n");
 		return 0;
 	}
 
+	pr_info("clk: Disabling unused clocks\n");
+
+	ret = clk_pm_runtime_get_all();
+	if (ret)
+		return ret;
+	/*
+	 * Grab the prepare lock to keep the clk topology stable while iterating
+	 * over clks.
+	 */
 	clk_prepare_lock();
 
 	hlist_for_each_entry(core, &clk_root_list, child_node)
@@ -1322,6 +1413,8 @@ static int __init clk_disable_unused(void)
 
 	clk_prepare_unlock();
 
+	clk_pm_runtime_put_all();
+
 	return 0;
 }
 late_initcall_sync(clk_disable_unused);
@@ -3627,9 +3720,6 @@ static int __clk_core_init(struct clk_core *core)
 	}
 
 	clk_core_reparent_orphans_nolock();
-
-
-	kref_init(&core->ref);
 out:
 	clk_pm_runtime_put(core);
 unlock:
@@ -3839,6 +3929,22 @@ static void clk_core_free_parent_map(struct clk_core *core)
 	kfree(core->parents);
 }
 
+/* Free memory allocated for a struct clk_core */
+static void __clk_release(struct kref *ref)
+{
+	struct clk_core *core = container_of(ref, struct clk_core, ref);
+
+	if (core->rpm_enabled) {
+		mutex_lock(&clk_rpm_list_lock);
+		hlist_del(&core->rpm_node);
+		mutex_unlock(&clk_rpm_list_lock);
+	}
+
+	clk_core_free_parent_map(core);
+	kfree_const(core->name);
+	kfree(core);
+}
+
 static struct clk *
 __clk_register(struct device *dev, struct device_node *np, struct clk_hw *hw)
 {
@@ -3859,6 +3965,8 @@ __clk_register(struct device *dev, struct device_node *np, struct clk_hw *hw)
 		goto fail_out;
 	}
 
+	kref_init(&core->ref);
+
 	core->name = kstrdup_const(init->name, GFP_KERNEL);
 	if (!core->name) {
 		ret = -ENOMEM;
@@ -3871,9 +3979,8 @@ __clk_register(struct device *dev, struct device_node *np, struct clk_hw *hw)
 	}
 	core->ops = init->ops;
 
-	if (dev && pm_runtime_enabled(dev))
-		core->rpm_enabled = true;
 	core->dev = dev;
+	clk_pm_runtime_init(core);
 	core->of_node = np;
 	if (dev && dev->driver)
 		core->owner = dev->driver->owner;
@@ -3913,12 +4020,10 @@ __clk_register(struct device *dev, struct device_node *np, struct clk_hw *hw)
 	hw->clk = NULL;
 
 fail_create_clk:
-	clk_core_free_parent_map(core);
 fail_parents:
 fail_ops:
-	kfree_const(core->name);
 fail_name:
-	kfree(core);
+	kref_put(&core->ref, __clk_release);
 fail_out:
 	return ERR_PTR(ret);
 }
@@ -3998,18 +4103,6 @@ int of_clk_hw_register(struct device_node *node, struct clk_hw *hw)
 }
 EXPORT_SYMBOL_GPL(of_clk_hw_register);
 
-/* Free memory allocated for a clock. */
-static void __clk_release(struct kref *ref)
-{
-	struct clk_core *core = container_of(ref, struct clk_core, ref);
-
-	lockdep_assert_held(&prepare_lock);
-
-	clk_core_free_parent_map(core);
-	kfree_const(core->name);
-	kfree(core);
-}
-
 /*
  * Empty clk_ops for unregistered clocks. These are used temporarily
  * after clk_unregister() was called on a clock and until last clock
@@ -4062,7 +4155,7 @@ static void clk_core_evict_parent_cache_subtree(struct clk_core *root,
 /* Remove this clk from all parent caches */
 static void clk_core_evict_parent_cache(struct clk_core *core)
 {
-	struct hlist_head **lists;
+	const struct hlist_head **lists;
 	struct clk_core *root;
 
 	lockdep_assert_held(&prepare_lock);