diff --git a/sound/firewire/fireface/ff-protocol-ff400.c b/sound/firewire/fireface/ff-protocol-ff400.c
index fd257051d4a4..374009545936 100644
--- a/sound/firewire/fireface/ff-protocol-ff400.c
+++ b/sound/firewire/fireface/ff-protocol-ff400.c
@@ -76,35 +76,6 @@ static void ff400_finish_session(struct snd_ff *ff)
 			   FF400_ISOC_COMM_STOP, &reg, sizeof(reg), 0);
 }
 
-static int ff400_switch_fetching_mode(struct snd_ff *ff, bool enable)
-{
-	__le32 *reg;
-	int i;
-	int err;
-
-	reg = kcalloc(18, sizeof(__le32), GFP_KERNEL);
-	if (reg == NULL)
-		return -ENOMEM;
-
-	if (!enable) {
-		/*
-		 * Each quadlet is corresponding to data channels in a data
-		 * blocks in reverse order. Precisely, quadlets for available
-		 * data channels should be enabled. Here, I take second best
-		 * to fetch PCM frames from all of data channels regardless of
-		 * stf.
-		 */
-		for (i = 0; i < 18; ++i)
-			reg[i] = cpu_to_le32(0x00000001);
-	}
-
-	err = snd_fw_transaction(ff->unit, TCODE_WRITE_BLOCK_REQUEST,
-				 SND_FF_REG_FETCH_PCM_FRAMES, reg,
-				 sizeof(__le32) * 18, 0);
-	kfree(reg);
-	return err;
-}
-
 static void ff400_handle_midi_msg(struct snd_ff *ff, __le32 *buf, size_t length)
 {
 	int i;
@@ -146,5 +117,4 @@ const struct snd_ff_protocol snd_ff_protocol_ff400 = {
 	.handle_midi_msg	= ff400_handle_midi_msg,
 	.begin_session		= ff400_begin_session,
 	.finish_session		= ff400_finish_session,
-	.switch_fetching_mode	= ff400_switch_fetching_mode,
 };
diff --git a/sound/firewire/fireface/ff-stream.c b/sound/firewire/fireface/ff-stream.c
index 59ca2e84d41c..e6fa6362dab7 100644
--- a/sound/firewire/fireface/ff-stream.c
+++ b/sound/firewire/fireface/ff-stream.c
@@ -73,10 +73,44 @@ static void release_resources(struct snd_ff *ff)
 	fw_iso_resources_free(&ff->rx_resources);
 }
 
+static int switch_fetching_mode(struct snd_ff *ff, bool enable)
+{
+	unsigned int count;
+	__le32 *reg;
+	int i;
+	int err;
+
+	count = 0;
+	for (i = 0; i < SND_FF_STREAM_MODES; ++i)
+		count = max(count, ff->spec->pcm_playback_channels[i]);
+
+	reg = kcalloc(count, sizeof(__le32), GFP_KERNEL);
+	if (!reg)
+		return -ENOMEM;
+
+	if (!enable) {
+		/*
+		 * Each quadlet is corresponding to data channels in a data
+		 * blocks in reverse order. Precisely, quadlets for available
+		 * data channels should be enabled. Here, I take second best
+		 * to fetch PCM frames from all of data channels regardless of
+		 * stf.
+		 */
+		for (i = 0; i < count; ++i)
+			reg[i] = cpu_to_le32(0x00000001);
+	}
+
+	err = snd_fw_transaction(ff->unit, TCODE_WRITE_BLOCK_REQUEST,
+				 SND_FF_REG_FETCH_PCM_FRAMES, reg,
+				 sizeof(__le32) * count, 0);
+	kfree(reg);
+	return err;
+}
+
 static inline void finish_session(struct snd_ff *ff)
 {
 	ff->spec->protocol->finish_session(ff);
-	ff->spec->protocol->switch_fetching_mode(ff, false);
+	switch_fetching_mode(ff, false);
 }
 
 static int init_stream(struct snd_ff *ff, enum amdtp_stream_direction dir)
@@ -188,7 +222,7 @@ int snd_ff_stream_start_duplex(struct snd_ff *ff, unsigned int rate)
 			goto error;
 		}
 
-		err = ff->spec->protocol->switch_fetching_mode(ff, true);
+		err = switch_fetching_mode(ff, true);
 		if (err < 0)
 			goto error;
 	}
diff --git a/sound/firewire/fireface/ff.h b/sound/firewire/fireface/ff.h
index 6e4a8197d3ca..17332d9ae3f2 100644
--- a/sound/firewire/fireface/ff.h
+++ b/sound/firewire/fireface/ff.h
@@ -111,7 +111,6 @@ struct snd_ff_protocol {
 	void (*handle_midi_msg)(struct snd_ff *ff, __le32 *buf, size_t length);
 	int (*begin_session)(struct snd_ff *ff, unsigned int rate);
 	void (*finish_session)(struct snd_ff *ff);
-	int (*switch_fetching_mode)(struct snd_ff *ff, bool enable);
 };
 
 extern const struct snd_ff_protocol snd_ff_protocol_ff800;