ALSA: firewire-motu: reserve/release isochronous resources in pcm.hw_params/hw_free callbacks

Once allocated, isochronous resources are available for packet
streaming, even if the streaming is cancelled. For this reason,
current implementation handles allocation of the resources and
starting packet streaming at the same time. However, this brings
complicated procedure to start packet streaming.

This commit separates the allocation and starting. The allocation is
done in pcm.hw_params callback and available till pcm.hw_free callback.
Even if any XRUN occurs, pcm.prepare callback is done to restart
packet streaming without releasing/allocating the resources.

There are two points to stop packet streaming; in pcm.hw_params and
pcm.prepare callbacks. The former point is a case that packet streaming
is already started for any MIDI substream then packet streaming is
requested with different sampling transfer frequency for any PCM
substream. The latter point is cases of any XRUN or packet queueing
error.
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/firewire/motu/motu-midi.c

@@ -18,8 +18,11 @@ static int midi_open(struct snd_rawmidi_substream *substream)
 
 	mutex_lock(&motu->mutex);
 
-	motu->substreams_counter++;
-	err = snd_motu_stream_start_duplex(motu, 0);
+	err = snd_motu_stream_reserve_duplex(motu, 0);
+	if (err >= 0) {
+		++motu->substreams_counter;
+		err = snd_motu_stream_start_duplex(motu);
+	}
 
 	mutex_unlock(&motu->mutex);
 
@@ -35,8 +38,9 @@ static int midi_close(struct snd_rawmidi_substream *substream)
 
 	mutex_lock(&motu->mutex);
 
-	motu->substreams_counter--;
+	--motu->substreams_counter;
 	snd_motu_stream_stop_duplex(motu);
+	snd_motu_stream_release_duplex(motu);
 
 	mutex_unlock(&motu->mutex);
 

sound/firewire/motu/motu-pcm.c

@@ -202,12 +202,16 @@ static int capture_hw_params(struct snd_pcm_substream *substream,
 		return err;
 
 	if (substream->runtime->status->state == SNDRV_PCM_STATE_OPEN) {
+		unsigned int rate = params_rate(hw_params);
+
 		mutex_lock(&motu->mutex);
-		motu->substreams_counter++;
+		err = snd_motu_stream_reserve_duplex(motu, rate);
+		if (err >= 0)
+			++motu->substreams_counter;
 		mutex_unlock(&motu->mutex);
 	}
 
-	return 0;
+	return err;
 }
 static int playback_hw_params(struct snd_pcm_substream *substream,
 			      struct snd_pcm_hw_params *hw_params)
@@ -221,12 +225,16 @@ static int playback_hw_params(struct snd_pcm_substream *substream,
 		return err;
 
 	if (substream->runtime->status->state == SNDRV_PCM_STATE_OPEN) {
+		unsigned int rate = params_rate(hw_params);
+
 		mutex_lock(&motu->mutex);
-		motu->substreams_counter++;
+		err = snd_motu_stream_reserve_duplex(motu, rate);
+		if (err >= 0)
+			++motu->substreams_counter;
 		mutex_unlock(&motu->mutex);
 	}
 
-	return 0;
+	return err;
 }
 
 static int capture_hw_free(struct snd_pcm_substream *substream)
@@ -236,9 +244,10 @@ static int capture_hw_free(struct snd_pcm_substream *substream)
 	mutex_lock(&motu->mutex);
 
 	if (substream->runtime->status->state != SNDRV_PCM_STATE_OPEN)
-		motu->substreams_counter--;
+		--motu->substreams_counter;
 
 	snd_motu_stream_stop_duplex(motu);
+	snd_motu_stream_release_duplex(motu);
 
 	mutex_unlock(&motu->mutex);
 
@@ -252,9 +261,10 @@ static int playback_hw_free(struct snd_pcm_substream *substream)
 	mutex_lock(&motu->mutex);
 
 	if (substream->runtime->status->state != SNDRV_PCM_STATE_OPEN)
-		motu->substreams_counter--;
+		--motu->substreams_counter;
 
 	snd_motu_stream_stop_duplex(motu);
+	snd_motu_stream_release_duplex(motu);
 
 	mutex_unlock(&motu->mutex);
 
@@ -267,7 +277,7 @@ static int capture_prepare(struct snd_pcm_substream *substream)
 	int err;
 
 	mutex_lock(&motu->mutex);
-	err = snd_motu_stream_start_duplex(motu, substream->runtime->rate);
+	err = snd_motu_stream_start_duplex(motu);
 	mutex_unlock(&motu->mutex);
 	if (err >= 0)
 		amdtp_stream_pcm_prepare(&motu->tx_stream);
@@ -280,7 +290,7 @@ static int playback_prepare(struct snd_pcm_substream *substream)
 	int err;
 
 	mutex_lock(&motu->mutex);
-	err = snd_motu_stream_start_duplex(motu, substream->runtime->rate);
+	err = snd_motu_stream_start_duplex(motu);
 	mutex_unlock(&motu->mutex);
 	if (err >= 0)
 		amdtp_stream_pcm_prepare(&motu->rx_stream);

sound/firewire/motu/motu-stream.c

@@ -60,20 +60,12 @@ static int keep_resources(struct snd_motu *motu, unsigned int rate,
 				fw_parent_device(motu->unit)->max_speed);
 }
 
-static int begin_session(struct snd_motu *motu, unsigned int rate)
+static int begin_session(struct snd_motu *motu)
 {
 	__be32 reg;
 	u32 data;
 	int err;
 
-	err = keep_resources(motu, rate, &motu->tx_stream);
-	if (err < 0)
-		return err;
-
-	err = keep_resources(motu, rate, &motu->rx_stream);
-	if (err < 0)
-		return err;
-
 	// Configure the unit to start isochronous communication.
 	err = snd_motu_transaction_read(motu, ISOC_COMM_CONTROL_OFFSET, &reg,
 					sizeof(reg));
@@ -116,9 +108,6 @@ static void finish_session(struct snd_motu *motu)
 	reg = cpu_to_be32(data);
 	snd_motu_transaction_write(motu, ISOC_COMM_CONTROL_OFFSET, &reg,
 				   sizeof(reg));
-
-	fw_iso_resources_free(&motu->tx_resources);
-	fw_iso_resources_free(&motu->rx_resources);
 }
 
 static int start_isoc_ctx(struct snd_motu *motu, struct amdtp_stream *stream)
@@ -136,11 +125,8 @@ static int start_isoc_ctx(struct snd_motu *motu, struct amdtp_stream *stream)
 	if (err < 0)
 		return err;
 
-	if (!amdtp_stream_wait_callback(stream, CALLBACK_TIMEOUT)) {
-		amdtp_stream_stop(stream);
-		fw_iso_resources_free(resources);
+	if (!amdtp_stream_wait_callback(stream, CALLBACK_TIMEOUT))
 		return -ETIMEDOUT;
-	}
 
 	return 0;
 }
@@ -172,6 +158,56 @@ int snd_motu_stream_cache_packet_formats(struct snd_motu *motu)
 	return 0;
 }
 
+int snd_motu_stream_reserve_duplex(struct snd_motu *motu, unsigned int rate)
+{
+	unsigned int curr_rate;
+	int err;
+
+	err = motu->spec->protocol->get_clock_rate(motu, &curr_rate);
+	if (err < 0)
+		return err;
+	if (rate == 0)
+		rate = curr_rate;
+
+	if (motu->substreams_counter == 0 || curr_rate != rate) {
+		finish_session(motu);
+
+		fw_iso_resources_free(&motu->tx_resources);
+		fw_iso_resources_free(&motu->rx_resources);
+
+		err = motu->spec->protocol->set_clock_rate(motu, rate);
+		if (err < 0) {
+			dev_err(&motu->unit->device,
+				"fail to set sampling rate: %d\n", err);
+			return err;
+		}
+
+		err = snd_motu_stream_cache_packet_formats(motu);
+		if (err < 0)
+			return err;
+
+		err = keep_resources(motu, rate, &motu->tx_stream);
+		if (err < 0)
+			return err;
+
+		err = keep_resources(motu, rate, &motu->rx_stream);
+		if (err < 0) {
+			fw_iso_resources_free(&motu->tx_resources);
+			return err;
+		}
+	}
+
+	return 0;
+}
+
+void snd_motu_stream_release_duplex(struct snd_motu *motu)
+{
+	if (motu->substreams_counter == 0) {
+		fw_iso_resources_free(&motu->tx_resources);
+		fw_iso_resources_free(&motu->rx_resources);
+	}
+}
+
 static int ensure_packet_formats(struct snd_motu *motu)
 {
 	__be32 reg;
@@ -198,46 +234,23 @@ static int ensure_packet_formats(struct snd_motu *motu)
 					  sizeof(reg));
 }
 
-int snd_motu_stream_start_duplex(struct snd_motu *motu, unsigned int rate)
+int snd_motu_stream_start_duplex(struct snd_motu *motu)
 {
-	const struct snd_motu_protocol *protocol = motu->spec->protocol;
-	unsigned int curr_rate;
 	int err = 0;
 
 	if (motu->substreams_counter == 0)
 		return 0;
 
-	err = snd_motu_stream_cache_packet_formats(motu);
-	if (err < 0)
-		return err;
-
-	// Stop stream if rate is different.
-	err = protocol->get_clock_rate(motu, &curr_rate);
-	if (err < 0) {
-		dev_err(&motu->unit->device,
-			"fail to get sampling rate: %d\n", err);
-		return err;
-	}
-	if (rate == 0)
-		rate = curr_rate;
-	if (rate != curr_rate ||
-	    amdtp_streaming_error(&motu->rx_stream) ||
+	if (amdtp_streaming_error(&motu->rx_stream) ||
 	    amdtp_streaming_error(&motu->tx_stream))
 		finish_session(motu);
 
 	if (!amdtp_stream_running(&motu->rx_stream)) {
-		err = protocol->set_clock_rate(motu, rate);
-		if (err < 0) {
-			dev_err(&motu->unit->device,
-				"fail to set sampling rate: %d\n", err);
-			return err;
-		}
-
 		err = ensure_packet_formats(motu);
 		if (err < 0)
 			return err;
 
-		err = begin_session(motu, rate);
+		err = begin_session(motu);
 		if (err < 0) {
 			dev_err(&motu->unit->device,
 				"fail to start isochronous comm: %d\n", err);
@@ -251,7 +264,7 @@ int snd_motu_stream_start_duplex(struct snd_motu *motu, unsigned int rate)
 			goto stop_streams;
 		}
 
-		err = protocol->switch_fetching_mode(motu, true);
+		err = motu->spec->protocol->switch_fetching_mode(motu, true);
 		if (err < 0) {
 			dev_err(&motu->unit->device,
 				"fail to enable frame fetching: %d\n", err);
@@ -264,7 +277,6 @@ int snd_motu_stream_start_duplex(struct snd_motu *motu, unsigned int rate)
 		if (err < 0) {
 			dev_err(&motu->unit->device,
 				"fail to start IR context: %d", err);
-			amdtp_stream_stop(&motu->rx_stream);
 			goto stop_streams;
 		}
 	}

sound/firewire/motu/motu.h

@@ -153,7 +153,9 @@ void snd_motu_transaction_unregister(struct snd_motu *motu);
 int snd_motu_stream_init_duplex(struct snd_motu *motu);
 void snd_motu_stream_destroy_duplex(struct snd_motu *motu);
 int snd_motu_stream_cache_packet_formats(struct snd_motu *motu);
-int snd_motu_stream_start_duplex(struct snd_motu *motu, unsigned int rate);
+int snd_motu_stream_reserve_duplex(struct snd_motu *motu, unsigned int rate);
+void snd_motu_stream_release_duplex(struct snd_motu *motu);
+int snd_motu_stream_start_duplex(struct snd_motu *motu);
 void snd_motu_stream_stop_duplex(struct snd_motu *motu);
 int snd_motu_stream_lock_try(struct snd_motu *motu);
 void snd_motu_stream_lock_release(struct snd_motu *motu);