ALSA: firewire-tascam: update isochronous resources when starting packet streaming after bus reset

After bus reset, isochronous resource manager releases all of allocated
isochronous resources. The nodes to restart packet streaming should
request reallocation of the resources.

However, between the bus-reset and invocation of 'struct fw_driver.update'
handler, ALSA PCM application can detect this situation by XRUN because
the target device cancelled to transmit packets once bus-reset occurs.

Due to the above mechanism, ALSA firewire-tascam driver just stops
packet streaming in the update handler, thus pcm.prepare handler
should request the reallocation.

This commit requests the reallocation in pcm.prepare callback when
bus generation is changed.
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/firewire/tascam/tascam-stream.c

@@ -321,7 +321,7 @@ int snd_tscm_stream_init_duplex(struct snd_tscm *tscm)
 	return err;
 }
 
-/* At bus reset, streaming is stopped and some registers are clear. */
+// At bus reset, streaming is stopped and some registers are clear.
 void snd_tscm_stream_update_duplex(struct snd_tscm *tscm)
 {
 	amdtp_stream_pcm_abort(&tscm->tx_stream);
@@ -390,6 +390,7 @@ void snd_tscm_stream_release_duplex(struct snd_tscm *tscm)
 
 int snd_tscm_stream_start_duplex(struct snd_tscm *tscm, unsigned int rate)
 {
+	unsigned int generation = tscm->rx_resources.generation;
 	int err;
 
 	if (tscm->substreams_counter == 0)
@@ -403,6 +404,16 @@ int snd_tscm_stream_start_duplex(struct snd_tscm *tscm, unsigned int rate)
 		finish_session(tscm);
 	}
 
+	if (generation != fw_parent_device(tscm->unit)->card->generation) {
+		err = fw_iso_resources_update(&tscm->tx_resources);
+		if (err < 0)
+			goto error;
+
+		err = fw_iso_resources_update(&tscm->rx_resources);
+		if (err < 0)
+			goto error;
+	}
+
 	if (!amdtp_stream_running(&tscm->rx_stream)) {
 		err = set_stream_formats(tscm, rate);
 		if (err < 0)