greybus: audio: schedule workqueue to perform codec cleanup on module removal

In response to codec module removal, user space is reported about
the event. In response to this, ALSA layer will update DAPM route
and cleanup DAPM states.
As a fallback mechanism, kernel can cleanup the DAPM state for codec
module. But, this would cause immediate playback (first trial) to fail,
since DSP is still in inconsistent state.
To avoid such situation, a workqueue is scheduled for codec cleanup
with timeout=50ms.
Thus, normally it is expected from above layers to update routes and
perform cleanup. However, fallback mechanism still holds good after
50ms.
Signed-off-by: Vaibhav Agarwal <vaibhav.agarwal@linaro.org>
Reviewed-by: Mark Greer <mgreer@animalcreek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/audio_codec.c

@@ -80,11 +80,7 @@ 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);
 	if (!gb_dai) {
 		dev_err(dai->dev, "%s: DAI not registered\n", dai->name);
@@ -93,6 +89,13 @@ static void gbcodec_shutdown(struct snd_pcm_substream *substream,
 
 	atomic_dec(&gb_dai->users);
 
+	if (!atomic_read(&gb->is_connected)) {
+		if (!atomic_read(&gb_dai->users))
+			wake_up_interruptible(&gb_dai->wait_queue);
+		return;
+	}
+
+	mutex_lock(&gb->lock);
 	/* deactivate rx/tx */
 	cportid = gb_dai->connection->intf_cport_id;
 
@@ -121,6 +124,11 @@ static void gbcodec_shutdown(struct snd_pcm_substream *substream,
 func_exit:
 	mutex_unlock(&gb->lock);
 
+	/*
+	if (!atomic_read(&gb_dai->users))
+		wake_up_interruptible(&gb_dai->wait_queue);
+		*/
+
 	return;
 }
 
@@ -290,8 +298,11 @@ 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))
+	if (!atomic_read(&gb->is_connected)) {
+		if (cmd == SNDRV_PCM_TRIGGER_STOP)
+			return 0;
 		return -ENODEV;
+	}
 
 	/* find the dai */
 	mutex_lock(&gb->lock);
@@ -443,9 +454,10 @@ static unsigned int gbcodec_read(struct snd_soc_codec *codec,
  */
 static void gb_audio_cleanup(struct gbaudio_codec_info *gb)
 {
-	int cportid, ret;
+	int cportid, ret, timeout_result;
 	struct gbaudio_dai *gb_dai;
 	struct gb_connection *connection;
+	long timeout = msecs_to_jiffies(50);	/* 50ms */
 	struct device *dev = gb->dev;
 
 	list_for_each_entry(gb_dai, &gb->dai_list, list) {
@@ -454,6 +466,16 @@ static void gb_audio_cleanup(struct gbaudio_codec_info *gb)
 		 * manually
 		 */
 		if (atomic_read(&gb_dai->users)) {
+			/* schedule a wait event */
+			timeout_result =
+				wait_event_interruptible_timeout(
+						gb_dai->wait_queue,
+						!atomic_read(&gb_dai->users),
+						timeout);
+			if (!timeout_result)
+				dev_warn(dev, "%s:DAI still in use.\n",
+					 gb_dai->name);
+
 			connection = gb_dai->connection;
 			/* PB active */
 			ret = gb_audio_apbridgea_stop_tx(connection, 0);
@@ -473,7 +495,6 @@ static void gb_audio_cleanup(struct gbaudio_codec_info *gb)
 			if (ret)
 				dev_info(dev, "%d:Failed during unregister cport\n",
 					 ret);
-			atomic_dec(&gb_dai->users);
 		}
 	}
 }
@@ -655,6 +676,7 @@ static int gb_audio_add_data_connection(struct gbaudio_codec_info *gbcodec,
 
 	connection->private = gbcodec;
 	atomic_set(&dai->users, 0);
+	init_waitqueue_head(&dai->wait_queue);
 	dai->data_cport = connection->intf_cport_id;
 	dai->connection = connection;
 	list_add(&dai->list, &gbcodec->dai_list);

drivers/staging/greybus/audio_codec.h

@@ -88,6 +88,7 @@ struct gbaudio_dai {
 	atomic_t users;
 	struct gb_connection *connection;
 	struct list_head list;
+	wait_queue_head_t wait_queue;
 };
 
 struct gbaudio_codec_info {