ALSA: dice: limit stream to current sampling transfer frequency.

In previous commit, ALSA Dice driver limits PCM substreams at current
sampling transfer frequency and current number of Multi bit linear audio
data channel. Thus, the driver has no need to start AMDTP streams at
the other sampling transfer frequency except for current one. This is due
to Dice interface design.

This commit limits AMDTP stream at current sampling transfer frequency,
according to the design.
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/firewire/dice/dice-stream.c

@@ -99,6 +99,7 @@ static int start_stream(struct snd_dice *dice, struct amdtp_stream *stream,
 			unsigned int rate)
 {
 	struct fw_iso_resources *resources;
+	__be32 reg[2];
 	unsigned int i, mode, pcm_chs, midi_ports;
 	bool double_pcm_frames;
 	int err;
@@ -108,14 +109,20 @@ static int start_stream(struct snd_dice *dice, struct amdtp_stream *stream,
 		goto end;
 	if (stream == &dice->tx_stream) {
 		resources = &dice->tx_resources;
-		pcm_chs = dice->tx_channels[mode];
-		midi_ports = dice->tx_midi_ports[mode];
+		err = snd_dice_transaction_read_tx(dice, TX_NUMBER_AUDIO,
+						   reg, sizeof(reg));
 	} else {
 		resources = &dice->rx_resources;
-		pcm_chs = dice->rx_channels[mode];
-		midi_ports = dice->rx_midi_ports[mode];
+		err = snd_dice_transaction_read_rx(dice, RX_NUMBER_AUDIO,
+						   reg, sizeof(reg));
 	}
 
+	if (err < 0)
+		goto end;
+
+	pcm_chs = be32_to_cpu(reg[0]);
+	midi_ports = be32_to_cpu(reg[1]);
+
 	/*
 	 * At 176.4/192.0 kHz, Dice has a quirk to transfer two PCM frames in
 	 * one data block of AMDTP packet. Thus sampling transfer frequency is
@@ -224,8 +231,10 @@ int snd_dice_stream_start_duplex(struct snd_dice *dice, unsigned int rate)
 	}
 	if (rate == 0)
 		rate = curr_rate;
-	if (rate != curr_rate)
-		stop_stream(dice, master);
+	if (rate != curr_rate) {
+		err = -EINVAL;
+		goto end;
+	}
 
 	if (!amdtp_stream_running(master)) {
 		stop_stream(dice, slave);