device property: Fix usecount for of_graph_get_port_parent()

Fix inconsistent use of of_graph_get_port_parent() where
asoc_simple_card_parse_graph_dai() does of_node_get() before
calling it while other callers do not. We can fix this by
not trashing the node passed to of_graph_get_port_parent().

Let's also make sure the callers have correct refcounts and remove
related incorrect of_node_put() calls for of_for_each_phandle
as that's done by of_phandle_iterator_next() except when
we break out of the loop early.

Let's fix both issues with a single patch to avoid kobject
refcounts getting messed up more if two patches are merged
separately.

Otherwise strange issues can happen caused by memory corruption
caused by too many kobject_del() calls such as:

BUG: sleeping function called from invalid context at
kernel/locking/mutex.c:747
...
(___might_sleep)
(__mutex_lock)
(mutex_lock_nested)
(kernfs_remove)
(kobject_del)
(kobject_put)
(of_get_next_parent)
(of_graph_get_port_parent)
(asoc_simple_card_parse_graph_dai [snd_soc_simple_card_utils])
(asoc_graph_card_probe [snd_soc_audio_graph_card])

Fixes: 0ef472a973eb ("of_graph: add of_graph_get_port_parent()")
Fixes: 2692c1c63c29 ("ASoC: add audio-graph-card support")
Fixes: 1689333f8311 ("ASoC: simple-card-utils: add asoc_simple_card_parse_graph_dai()")
Signed-off-by: Tony Lindgren <tony@atomide.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Tested-by: Antonio Borneo <borneo.antonio@gmail.com>
Tested-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 15 insertions, 2 deletions

diff --git a/drivers/of/property.c b/drivers/of/property.c
index eda50b4be934..067f9fab7b77 100644
--- a/drivers/of/property.c
+++ b/drivers/of/property.c
@@ -708,6 +708,15 @@ struct device_node *of_graph_get_port_parent(struct device_node *node)
 {
 	unsigned int depth;
 
+	if (!node)
+		return NULL;
+
+	/*
+	 * Preserve usecount for passed in node as of_get_next_parent()
+	 * will do of_node_put() on it.
+	 */
+	of_node_get(node);
+
 	/* Walk 3 levels up only if there is 'ports' node. */
 	for (depth = 3; depth && node; depth--) {
 		node = of_get_next_parent(node);
@@ -728,12 +737,16 @@ EXPORT_SYMBOL(of_graph_get_port_parent);
 struct device_node *of_graph_get_remote_port_parent(
 			       const struct device_node *node)
 {
-	struct device_node *np;
+	struct device_node *np, *pp;
 
 	/* Get remote endpoint node. */
 	np = of_graph_get_remote_endpoint(node);
 
-	return of_graph_get_port_parent(np);
+	pp = of_graph_get_port_parent(np);
+
+	of_node_put(np);
+
+	return pp;
 }
 EXPORT_SYMBOL(of_graph_get_remote_port_parent);