greybus: gb-audio: Activate TX CPort in PCM workqueue

Currently, the I2S TX CPort is configured and activated during
the Greybus audio initialization.  Unfortunately, this prevents
the audio driver from ever changing the I2S configuration.

To allow the I2S configuration to change according to ASOC requests,
move the CPort activation & deactivation to the audio-pcm workqueue.
Now, when audio is running but the CPort is not active, it will be
activated.  When audio is not running and the CPort is active, it
will be deactivated.

This has the side-effect of sending the first piece of audio data
immediately after activating the CPort which is really how it should
work anyway.
Signed-off-by: Mark A. Greer <mgreer@animalcreek.com>
Acked-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/audio-gb-cmds.c

@@ -165,17 +165,8 @@ int gb_i2s_mgmt_setup(struct gb_connection *connection)
 
 	ret = gb_i2s_mgmt_set_samples_per_message(connection,
 						  CONFIG_SAMPLES_PER_MSG);
-	if (ret) {
+	if (ret)
 		pr_err("set_samples_per_msg failed: %d\n", ret);
-		goto free_get_cfg;
-	}
-
-	ret = gb_i2s_mgmt_activate_cport(connection,
-					 CONFIG_I2S_REMOTE_DATA_CPORT);
-	if (ret) {
-		pr_err("activate_cport failed: %d\n", ret);
-		goto free_get_cfg;
-	}
 
 free_get_cfg:
 	kfree(get_cfg);

drivers/staging/greybus/audio-pcm.c

@@ -32,15 +32,33 @@ static void gb_pcm_work(struct work_struct *work)
 	struct snd_pcm_substream *substream = snd_dev->substream;
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	unsigned int stride, frames, oldptr;
-	int period_elapsed;
+	int period_elapsed, ret;
 	char *address;
 	long len;
 
 	if (!snd_dev)
 		return;
 
-	if (!atomic_read(&snd_dev->running))
+	if (!atomic_read(&snd_dev->running)) {
+		if (snd_dev->cport_active) {
+			ret = gb_i2s_mgmt_deactivate_cport(
+						snd_dev->mgmt_connection,
+						CONFIG_I2S_REMOTE_DATA_CPORT);
+			if (ret) /* XXX Do what else with failure? */
+				pr_err("deactivate_cport failed: %d\n", ret);
+
+			snd_dev->cport_active = false;
+		}
+
 		return;
+	} else if (!snd_dev->cport_active) {
+		ret = gb_i2s_mgmt_activate_cport(snd_dev->mgmt_connection,
+						 CONFIG_I2S_REMOTE_DATA_CPORT);
+		if (ret)
+			pr_err("activate_cport failed: %d\n", ret);
+
+		snd_dev->cport_active = true;
+	}
 
 	address = runtime->dma_area + snd_dev->hwptr_done;
 
@@ -88,6 +106,7 @@ static enum hrtimer_restart gb_pcm_timer_function(struct hrtimer *hrtimer)
 void gb_pcm_hrtimer_start(struct gb_snd *snd_dev)
 {
 	atomic_set(&snd_dev->running, 1);
+	queue_work(snd_dev->workqueue, &snd_dev->work); /* Activates CPort */
 	hrtimer_start(&snd_dev->timer, ns_to_ktime(CONFIG_PERIOD_NS),
 						HRTIMER_MODE_REL);
 }
@@ -96,6 +115,7 @@ void gb_pcm_hrtimer_stop(struct gb_snd *snd_dev)
 {
 	atomic_set(&snd_dev->running, 0);
 	hrtimer_cancel(&snd_dev->timer);
+	queue_work(snd_dev->workqueue, &snd_dev->work); /* Deactivates CPort */
 }
 
 static int gb_pcm_hrtimer_init(struct gb_snd *snd_dev)

drivers/staging/greybus/audio.c

@@ -292,13 +292,11 @@ static int gb_i2s_mgmt_connection_init(struct gb_connection *connection)
 
 	if (!snd_dev->send_data_req_buf) {
 		ret = -ENOMEM;
-		goto err_deactivate_cport;
+		goto err_free_snd_dev;
 	}
 
 	return 0;
 
-err_deactivate_cport:
-	gb_i2s_mgmt_deactivate_cport(connection, CONFIG_I2S_REMOTE_DATA_CPORT);
 err_free_snd_dev:
 	gb_free_snd(snd_dev);
 	return ret;
@@ -307,12 +305,6 @@ static int gb_i2s_mgmt_connection_init(struct gb_connection *connection)
 static void gb_i2s_mgmt_connection_exit(struct gb_connection *connection)
 {
 	struct gb_snd *snd_dev = (struct gb_snd *)connection->private;
-	int ret;
-
-	ret = gb_i2s_mgmt_deactivate_cport(connection,
-					   CONFIG_I2S_REMOTE_DATA_CPORT);
-	if (ret)
-		pr_err("deactivate_cport failed: %d\n", ret);
 
 	kfree(snd_dev->send_data_req_buf);
 	snd_dev->send_data_req_buf = NULL;

drivers/staging/greybus/audio.h

@@ -53,6 +53,7 @@ struct gb_snd {
 	struct snd_pcm_substream	*substream;
 	struct hrtimer			timer;
 	atomic_t			running;
+	bool				cport_active;
 	struct workqueue_struct		*workqueue;
 	struct work_struct		work;
 	int				hwptr_done;