[PATCH] device property: Fix usecount for of_graph_get_port_parent()

[Tony Lindgren]

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 make sure the users 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().

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()")
Cc: Mark Brown <broo...@kernel.org>
Cc: Takashi Iwai <ti...@suse.com>
Cc: Kuninori Morimoto <kuninori.morimoto...@renesas.com>
Cc: alsa-de...@alsa-project.org
Signed-off-by: Tony Lindgren <t...@atomide.com>
---
 drivers/of/property.c                 | 9 +++++++++
 sound/soc/generic/audio-graph-card.c  | 5 +----
 sound/soc/generic/simple-card-utils.c | 5 -----
 3 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/drivers/of/property.c b/drivers/of/property.c
--- 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);
diff --git a/sound/soc/generic/audio-graph-card.c 
b/sound/soc/generic/audio-graph-card.c
--- a/sound/soc/generic/audio-graph-card.c
+++ b/sound/soc/generic/audio-graph-card.c
@@ -224,7 +224,6 @@ static int asoc_graph_card_parse_of(struct graph_card_data 
*priv)
 
        of_for_each_phandle(&it, rc, node, "dais", NULL, 0) {
                ret = asoc_graph_card_dai_link_of(it.node, priv, idx++);
-               of_node_put(it.node);
                if (ret < 0)
                        return ret;
        }
@@ -239,10 +238,8 @@ static int asoc_graph_get_dais_count(struct device *dev)
        int count = 0;
        int rc;
 
-       of_for_each_phandle(&it, rc, node, "dais", NULL, 0) {
+       of_for_each_phandle(&it, rc, node, "dais", NULL, 0)
                count++;
-               of_node_put(it.node);
-       }
 
        return count;
 }
diff --git a/sound/soc/generic/simple-card-utils.c 
b/sound/soc/generic/simple-card-utils.c
--- a/sound/soc/generic/simple-card-utils.c
+++ b/sound/soc/generic/simple-card-utils.c
@@ -282,11 +282,6 @@ int asoc_simple_card_parse_graph_dai(struct device_node 
*ep,
        if (!dai_name)
                return 0;
 
-       /*
-        * of_graph_get_port_parent() will call
-        * of_node_put(). So, call of_node_get() here
-        */
-       of_node_get(ep);
        node = of_graph_get_port_parent(ep);
 
        /* Get dai->name */
-- 
2.13.2