greybus: audio: use variable 'is_connected' to maintain module state

there is race condition between _disconnect() request &
stop_trigger() in case of abrupt module removal.
And sometimes this can lead to deadlock while acquiring
codec_info->lock.
To avoid such situation, atomic variable is used to maintain
codec connected state.
During dai operations (trigger, shutdown, etc.), 'is_connected'
variable is validated to avoid unnecessary lock acquire in
case module already removed.
Signed-off-by: Vaibhav Agarwal <vaibhav.agarwal@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/audio_codec.c

@@ -44,6 +44,9 @@ static int gbcodec_startup(struct snd_pcm_substream *substream,
 	struct gbaudio_dai *gb_dai;
 	struct gbaudio_codec_info *gb = dev_get_drvdata(dai->dev);
 
+	if (!atomic_read(&gb->is_connected))
+		return -ENODEV;
+
 	/* find the dai */
 	mutex_lock(&gb->lock);
 	gb_dai = gbaudio_find_dai(gb, -1, dai->name);
@@ -77,6 +80,9 @@ static void gbcodec_shutdown(struct snd_pcm_substream *substream,
 	struct gbaudio_dai *gb_dai;
 	struct gbaudio_codec_info *gb = dev_get_drvdata(dai->dev);
 
+	if (!atomic_read(&gb->is_connected))
+		return;
+
 	/* find the dai */
 	mutex_lock(&gb->lock);
 	gb_dai = gbaudio_find_dai(gb, -1, dai->name);
@@ -129,6 +135,9 @@ static int gbcodec_hw_params(struct snd_pcm_substream *substream,
 	struct gbaudio_dai *gb_dai;
 	struct gbaudio_codec_info *gb = dev_get_drvdata(dai->dev);
 
+	if (!atomic_read(&gb->is_connected))
+		return -ENODEV;
+
 	/* find the dai */
 	mutex_lock(&gb->lock);
 	gb_dai = gbaudio_find_dai(gb, -1, dai->name);
@@ -204,6 +213,9 @@ static int gbcodec_prepare(struct snd_pcm_substream *substream,
 	struct gbaudio_dai *gb_dai;
 	struct gbaudio_codec_info *gb = dev_get_drvdata(dai->dev);
 
+	if (!atomic_read(&gb->is_connected))
+		return -ENODEV;
+
 	/* find the dai */
 	mutex_lock(&gb->lock);
 	gb_dai = gbaudio_find_dai(gb, -1, dai->name);
@@ -278,6 +290,9 @@ static int gbcodec_trigger(struct snd_pcm_substream *substream, int cmd,
 	struct gbaudio_dai *gb_dai;
 	struct gbaudio_codec_info *gb = dev_get_drvdata(dai->dev);
 
+	if (!atomic_read(&gb->is_connected))
+		return -ENODEV;
+
 	/* find the dai */
 	mutex_lock(&gb->lock);
 	gb_dai = gbaudio_find_dai(gb, -1, dai->name);
@@ -776,6 +791,7 @@ static int gb_audio_probe(struct gb_bundle *bundle,
 	desc.devices = 0x2; /* todo */
 	gbcodec->manager_id = gb_audio_manager_add(&desc);
 
+	atomic_set(&gbcodec->is_connected, 1);
 	list_add(&gbcodec->list, &gb_codec_list);
 	dev_dbg(dev, "Add GB Audio device:%s\n", gbcodec->name);
 	mutex_unlock(&gb_codec_list_lock);
@@ -809,6 +825,7 @@ static void gb_audio_disconnect(struct gb_bundle *bundle)
 	struct gbaudio_dai *dai, *_dai;
 
 	mutex_lock(&gb_codec_list_lock);
+	atomic_set(&gbcodec->is_connected, 0);
 	list_del(&gbcodec->list);
 	/* inform uevent to above layers */
 	gb_audio_manager_remove(gbcodec->manager_id);

drivers/staging/greybus/audio_codec.h

@@ -108,6 +108,15 @@ struct gbaudio_codec_info {
 	int manager_id;
 	char name[NAME_SIZE];
 
+	/*
+	 * there can be a rece condition between gb_audio_disconnect()
+	 * and dai->trigger from above ASoC layer.
+	 * To avoid any deadlock over codec_info->lock, atomic variable
+	 * is used.
+	 */
+	atomic_t is_connected;
+	struct mutex lock;
+
 	/* soc related data */
 	struct snd_soc_codec *codec;
 	struct device *dev;
@@ -139,7 +148,6 @@ struct gbaudio_codec_info {
 	struct list_head widget_list;
 	struct list_head codec_ctl_list;
 	struct list_head widget_ctl_list;
-	struct mutex lock;
 };
 
 struct gbaudio_dai *gbaudio_find_dai(struct gbaudio_codec_info *gbcodec,

drivers/staging/greybus/audio_topology.c

@@ -140,6 +140,9 @@ static int gbcodec_mixer_ctl_get(struct snd_kcontrol *kcontrol,
 	struct snd_soc_codec *codec = snd_kcontrol_chip(kcontrol);
 	struct gbaudio_codec_info *gb = snd_soc_codec_get_drvdata(codec);
 
+	if (!atomic_read(&gb->is_connected))
+		return -ENODEV;
+
 	data = (struct gbaudio_ctl_pvt *)kcontrol->private_value;
 	info = (struct gb_audio_ctl_elem_info *)data->info;
 
@@ -187,6 +190,9 @@ static int gbcodec_mixer_ctl_put(struct snd_kcontrol *kcontrol,
 	struct snd_soc_codec *codec = snd_kcontrol_chip(kcontrol);
 	struct gbaudio_codec_info *gb = snd_soc_codec_get_drvdata(codec);
 
+	if (!atomic_read(&gb->is_connected))
+		return -ENODEV;
+
 	data = (struct gbaudio_ctl_pvt *)kcontrol->private_value;
 	info = (struct gb_audio_ctl_elem_info *)data->info;
 
@@ -281,6 +287,9 @@ static int gbcodec_mixer_dapm_ctl_get(struct snd_kcontrol *kcontrol,
 	struct snd_soc_codec *codec = widget->codec;
 	struct gbaudio_codec_info *gb = snd_soc_codec_get_drvdata(codec);
 
+	if (!atomic_read(&gb->is_connected))
+		return -ENODEV;
+
 	data = (struct gbaudio_ctl_pvt *)kcontrol->private_value;
 	info = (struct gb_audio_ctl_elem_info *)data->info;
 
@@ -315,6 +324,9 @@ static int gbcodec_mixer_dapm_ctl_put(struct snd_kcontrol *kcontrol,
 	struct snd_soc_codec *codec = widget->codec;
 	struct gbaudio_codec_info *gb = snd_soc_codec_get_drvdata(codec);
 
+	if (!atomic_read(&gb->is_connected))
+		return -ENODEV;
+
 	data = (struct gbaudio_ctl_pvt *)kcontrol->private_value;
 	info = (struct gb_audio_ctl_elem_info *)data->info;