diff --git a/sound/usb/line6/capture.c b/sound/usb/line6/capture.c
index f518fbb..91d1562 100644
--- a/sound/usb/line6/capture.c
+++ b/sound/usb/line6/capture.c
@@ -29,10 +29,10 @@ static int submit_audio_in_urb(struct snd_line6_pcm *line6pcm)
 	int ret;
 	struct urb *urb_in;
 
-	index =
-	    find_first_zero_bit(&line6pcm->in.active_urbs, LINE6_ISO_BUFFERS);
+	index = find_first_zero_bit(
+		&line6pcm->in.active_urbs, line6pcm->line6->iso_buffers);
 
-	if (index < 0 || index >= LINE6_ISO_BUFFERS) {
+	if (index < 0 || index >= line6pcm->line6->iso_buffers) {
 		dev_err(line6pcm->line6->ifcdev, "no free URB found\n");
 		return -EINVAL;
 	}
@@ -44,13 +44,13 @@ static int submit_audio_in_urb(struct snd_line6_pcm *line6pcm)
 		struct usb_iso_packet_descriptor *fin =
 		    &urb_in->iso_frame_desc[i];
 		fin->offset = urb_size;
-		fin->length = line6pcm->max_packet_size;
-		urb_size += line6pcm->max_packet_size;
+		fin->length = line6pcm->max_packet_size_in;
+		urb_size += line6pcm->max_packet_size_in;
 	}
 
 	urb_in->transfer_buffer =
 	    line6pcm->in.buffer +
-	    index * LINE6_ISO_PACKETS * line6pcm->max_packet_size;
+	    index * LINE6_ISO_PACKETS * line6pcm->max_packet_size_in;
 	urb_in->transfer_buffer_length = urb_size;
 	urb_in->context = line6pcm;
 
@@ -73,7 +73,7 @@ int line6_submit_audio_in_all_urbs(struct snd_line6_pcm *line6pcm)
 {
 	int ret = 0, i;
 
-	for (i = 0; i < LINE6_ISO_BUFFERS; ++i) {
+	for (i = 0; i < line6pcm->line6->iso_buffers; ++i) {
 		ret = submit_audio_in_urb(line6pcm);
 		if (ret < 0)
 			break;
@@ -90,7 +90,9 @@ void line6_capture_copy(struct snd_line6_pcm *line6pcm, char *fbuf, int fsize)
 	struct snd_pcm_substream *substream =
 	    get_substream(line6pcm, SNDRV_PCM_STREAM_CAPTURE);
 	struct snd_pcm_runtime *runtime = substream->runtime;
-	const int bytes_per_frame = line6pcm->properties->bytes_per_frame;
+	const int bytes_per_frame =
+		line6pcm->properties->bytes_per_channel *
+		line6pcm->properties->capture_hw.channels_max;
 	int frames = fsize / bytes_per_frame;
 
 	if (runtime == NULL)
@@ -154,7 +156,7 @@ static void audio_in_callback(struct urb *urb)
 	line6pcm->in.last_frame = urb->start_frame;
 
 	/* find index of URB */
-	for (index = 0; index < LINE6_ISO_BUFFERS; ++index)
+	for (index = 0; index < line6pcm->line6->iso_buffers; ++index)
 		if (urb == line6pcm->in.urbs[index])
 			break;
 
@@ -173,17 +175,27 @@ static void audio_in_callback(struct urb *urb)
 		fbuf = urb->transfer_buffer + fin->offset;
 		fsize = fin->actual_length;
 
-		if (fsize > line6pcm->max_packet_size) {
+		if (fsize > line6pcm->max_packet_size_in) {
 			dev_err(line6pcm->line6->ifcdev,
 				"driver and/or device bug: packet too large (%d > %d)\n",
-				fsize, line6pcm->max_packet_size);
+				fsize, line6pcm->max_packet_size_in);
 		}
 
 		length += fsize;
 
-		/* the following assumes LINE6_ISO_PACKETS == 1: */
+		BUILD_BUG_ON_MSG(LINE6_ISO_PACKETS != 1,
+			"The following code assumes LINE6_ISO_PACKETS == 1");
+		/* TODO:
+		 * Also, if iso_buffers != 2, the prev frame is almost random at
+		 * playback side.
+		 * This needs to be redesigned. It should be "stable", but we may
+		 * experience sync problems on such high-speed configs.
+		 */
+
 		line6pcm->prev_fbuf = fbuf;
-		line6pcm->prev_fsize = fsize;
+		line6pcm->prev_fsize = fsize /
+			(line6pcm->properties->bytes_per_channel *
+			line6pcm->properties->capture_hw.channels_max);
 
 		if (!test_bit(LINE6_STREAM_IMPULSE, &line6pcm->in.running) &&
 		    test_bit(LINE6_STREAM_PCM, &line6pcm->in.running) &&
@@ -247,8 +259,13 @@ int line6_create_audio_in_urbs(struct snd_line6_pcm *line6pcm)
 	struct usb_line6 *line6 = line6pcm->line6;
 	int i;
 
+	line6pcm->in.urbs = kzalloc(
+		sizeof(struct urb *) * line6->iso_buffers, GFP_KERNEL);
+	if (line6pcm->in.urbs == NULL)
+		return -ENOMEM;
+
 	/* create audio URBs and fill in constant values: */
-	for (i = 0; i < LINE6_ISO_BUFFERS; ++i) {
+	for (i = 0; i < line6->iso_buffers; ++i) {
 		struct urb *urb;
 
 		/* URB for audio in: */
diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c
index 81b7da8..efeb16a8 100644
--- a/sound/usb/line6/driver.c
+++ b/sound/usb/line6/driver.c
@@ -462,13 +462,17 @@ static void line6_destruct(struct snd_card *card)
 static void line6_get_interval(struct usb_line6 *line6)
 {
 	struct usb_device *usbdev = line6->usbdev;
-	struct usb_host_endpoint *ep;
-	unsigned pipe = usb_rcvintpipe(usbdev, line6->properties->ep_ctrl_r);
-	unsigned epnum = usb_pipeendpoint(pipe);
-
-	ep = usbdev->ep_in[epnum];
+	struct usb_host_endpoint *ep = usbdev->ep_in[line6->properties->ep_ctrl_r];
 	if (ep) {
 		line6->interval = ep->desc.bInterval;
+		if (usbdev->speed == USB_SPEED_LOW) {
+			line6->intervals_per_second = USB_LOW_INTERVALS_PER_SECOND;
+			line6->iso_buffers = USB_LOW_ISO_BUFFERS;
+		} else {
+			line6->intervals_per_second = USB_HIGH_INTERVALS_PER_SECOND;
+			line6->iso_buffers = USB_HIGH_ISO_BUFFERS;
+		}
+
 		line6->max_packet_size = le16_to_cpu(ep->desc.wMaxPacketSize);
 	} else {
 		dev_err(line6->ifcdev,
@@ -558,6 +562,7 @@ int line6_probe(struct usb_interface *interface,
 	/* query interface number */
 	interface_number = interface->cur_altsetting->desc.bInterfaceNumber;
 
+	/* TODO reserves the bus bandwidth even without actual transfer */
 	ret = usb_set_interface(usbdev, interface_number,
 				properties->altsetting);
 	if (ret < 0) {
diff --git a/sound/usb/line6/driver.h b/sound/usb/line6/driver.h
index 7da643e..2d32139 100644
--- a/sound/usb/line6/driver.h
+++ b/sound/usb/line6/driver.h
@@ -18,14 +18,20 @@
 
 #include "midi.h"
 
-#define USB_INTERVALS_PER_SECOND 1000
+/* USB 1.1 speed configuration */
+#define USB_LOW_INTERVALS_PER_SECOND 1000
+#define USB_LOW_ISO_BUFFERS 2
+
+/* USB 2.0+ speed configuration */
+#define USB_HIGH_INTERVALS_PER_SECOND 8000
+#define USB_HIGH_ISO_BUFFERS 16
 
 /* Fallback USB interval and max packet size values */
 #define LINE6_FALLBACK_INTERVAL 10
 #define LINE6_FALLBACK_MAXPACKETSIZE 16
 
 #define LINE6_TIMEOUT 1
-#define LINE6_BUFSIZE_LISTEN 32
+#define LINE6_BUFSIZE_LISTEN 64
 #define LINE6_MESSAGE_MAXLEN 256
 
 /*
@@ -109,10 +115,15 @@ struct usb_line6 {
 	/* Properties */
 	const struct line6_properties *properties;
 
-	/* Interval (ms) */
+	/* Interval for data USB packets */
 	int interval;
+	/* ...for isochronous transfers framing */
+	int intervals_per_second;
+
+	/* Number of isochronous URBs used for frame transfers */
+	int iso_buffers;
 
-	/* Maximum size of USB packet */
+	/* Maximum size of data USB packet */
 	int max_packet_size;
 
 	/* Device representing the USB interface */
diff --git a/sound/usb/line6/pcm.c b/sound/usb/line6/pcm.c
index 41aa335..e1913d3 100644
--- a/sound/usb/line6/pcm.c
+++ b/sound/usb/line6/pcm.c
@@ -104,7 +104,7 @@ static void line6_unlink_audio_urbs(struct snd_line6_pcm *line6pcm,
 {
 	int i;
 
-	for (i = 0; i < LINE6_ISO_BUFFERS; i++) {
+	for (i = 0; i < line6pcm->line6->iso_buffers; i++) {
 		if (test_bit(i, &pcms->active_urbs)) {
 			if (!test_and_set_bit(i, &pcms->unlink_urbs))
 				usb_unlink_urb(pcms->urbs[i]);
@@ -124,7 +124,7 @@ static void line6_wait_clear_audio_urbs(struct snd_line6_pcm *line6pcm,
 
 	do {
 		alive = 0;
-		for (i = 0; i < LINE6_ISO_BUFFERS; i++) {
+		for (i = 0; i < line6pcm->line6->iso_buffers; i++) {
 			if (test_bit(i, &pcms->active_urbs))
 				alive++;
 		}
@@ -146,15 +146,20 @@ get_stream(struct snd_line6_pcm *line6pcm, int direction)
 }
 
 /* allocate a buffer if not opened yet;
- * call this in line6pcm.state_change mutex
+ * call this in line6pcm.state_mutex
  */
 static int line6_buffer_acquire(struct snd_line6_pcm *line6pcm,
-				struct line6_pcm_stream *pstr, int type)
+				struct line6_pcm_stream *pstr, int direction, int type)
 {
+	const int pkt_size =
+		(direction == SNDRV_PCM_STREAM_PLAYBACK) ?
+			line6pcm->max_packet_size_out :
+			line6pcm->max_packet_size_in;
+
 	/* Invoked multiple times in a row so allocate once only */
 	if (!test_and_set_bit(type, &pstr->opened) && !pstr->buffer) {
-		pstr->buffer = kmalloc(LINE6_ISO_BUFFERS * LINE6_ISO_PACKETS *
-				       line6pcm->max_packet_size, GFP_KERNEL);
+		pstr->buffer = kmalloc(line6pcm->line6->iso_buffers *
+							   LINE6_ISO_PACKETS * pkt_size, GFP_KERNEL);
 		if (!pstr->buffer)
 			return -ENOMEM;
 	}
@@ -162,12 +167,11 @@ static int line6_buffer_acquire(struct snd_line6_pcm *line6pcm,
 }
 
 /* free a buffer if all streams are closed;
- * call this in line6pcm.state_change mutex
+ * call this in line6pcm.state_mutex
  */
 static void line6_buffer_release(struct snd_line6_pcm *line6pcm,
 				 struct line6_pcm_stream *pstr, int type)
 {
-
 	clear_bit(type, &pstr->opened);
 	if (!pstr->opened) {
 		line6_wait_clear_audio_urbs(line6pcm, pstr);
@@ -194,6 +198,7 @@ static int line6_stream_start(struct snd_line6_pcm *line6pcm, int direction,
 		else
 			ret = line6_submit_audio_in_all_urbs(line6pcm);
 	}
+
 	if (ret < 0)
 		clear_bit(type, &pstr->running);
 	spin_unlock_irqrestore(&pstr->lock, flags);
@@ -434,24 +439,30 @@ static struct snd_kcontrol_new line6_controls[] = {
 /*
 	Cleanup the PCM device.
 */
-static void cleanup_urbs(struct line6_pcm_stream *pcms)
+static void cleanup_urbs(struct line6_pcm_stream *pcms, int iso_buffers)
 {
 	int i;
 
-	for (i = 0; i < LINE6_ISO_BUFFERS; i++) {
+	/* Most likely impossible in current code... */
+	if (pcms->urbs == NULL)
+		return;
+
+	for (i = 0; i < iso_buffers; i++) {
 		if (pcms->urbs[i]) {
 			usb_kill_urb(pcms->urbs[i]);
 			usb_free_urb(pcms->urbs[i]);
 		}
 	}
+	kfree(pcms->urbs);
+	pcms->urbs = NULL;
 }
 
 static void line6_cleanup_pcm(struct snd_pcm *pcm)
 {
 	struct snd_line6_pcm *line6pcm = snd_pcm_chip(pcm);
 
-	cleanup_urbs(&line6pcm->out);
-	cleanup_urbs(&line6pcm->in);
+	cleanup_urbs(&line6pcm->out, line6pcm->line6->iso_buffers);
+	cleanup_urbs(&line6pcm->in, line6pcm->line6->iso_buffers);
 	kfree(line6pcm);
 }
 
@@ -523,12 +534,12 @@ int line6_init_pcm(struct usb_line6 *line6,
 	line6pcm->volume_monitor = 255;
 	line6pcm->line6 = line6;
 
-	/* Read and write buffers are sized identically, so choose minimum */
-	line6pcm->max_packet_size = min(
-			usb_maxpacket(line6->usbdev,
-				usb_rcvisocpipe(line6->usbdev, ep_read), 0),
-			usb_maxpacket(line6->usbdev,
-				usb_sndisocpipe(line6->usbdev, ep_write), 1));
+	line6pcm->max_packet_size_in =
+		usb_maxpacket(line6->usbdev,
+			usb_rcvisocpipe(line6->usbdev, ep_read), 0);
+	line6pcm->max_packet_size_out =
+		usb_maxpacket(line6->usbdev,
+			usb_sndisocpipe(line6->usbdev, ep_write), 1);
 
 	spin_lock_init(&line6pcm->out.lock);
 	spin_lock_init(&line6pcm->in.lock);
diff --git a/sound/usb/line6/pcm.h b/sound/usb/line6/pcm.h
index 508410a..58d36f9 100644
--- a/sound/usb/line6/pcm.h
+++ b/sound/usb/line6/pcm.h
@@ -20,9 +20,6 @@
 
 #include "driver.h"
 
-/* number of URBs */
-#define LINE6_ISO_BUFFERS	2
-
 /*
 	number of USB frames per URB
 	The Line 6 Windows driver always transmits two frames per packet, but
@@ -31,7 +28,8 @@
 */
 #define LINE6_ISO_PACKETS	1
 
-/* in a "full speed" device (such as the PODxt Pro) this means 1ms */
+/* in a "full speed" device (such as the PODxt Pro) this means 1ms,
+   for "high speed" it's 1/8ms */
 #define LINE6_ISO_INTERVAL	1
 
 #define LINE6_IMPULSE_DEFAULT_PERIOD 100
@@ -85,12 +83,12 @@ enum {
 struct line6_pcm_properties {
 	struct snd_pcm_hardware playback_hw, capture_hw;
 	struct snd_pcm_hw_constraint_ratdens rates;
-	int bytes_per_frame;
+	int bytes_per_channel;
 };
 
 struct line6_pcm_stream {
 	/* allocated URBs */
-	struct urb *urbs[LINE6_ISO_BUFFERS];
+	struct urb **urbs;
 
 	/* Temporary buffer;
 	 * Since the packet size is not known in advance, this buffer is
@@ -157,11 +155,12 @@ struct snd_line6_pcm {
 	/* Previously captured frame (for software monitoring) */
 	unsigned char *prev_fbuf;
 
-	/* Size of previously captured frame (for software monitoring) */
+	/* Size of previously captured frame (for software monitoring/sync) */
 	int prev_fsize;
 
 	/* Maximum size of USB packet */
-	int max_packet_size;
+	int max_packet_size_in;
+	int max_packet_size_out;
 
 	/* PCM playback volume (left and right) */
 	int volume_playback[2];
diff --git a/sound/usb/line6/playback.c b/sound/usb/line6/playback.c
index 97ed593..4833c51 100644
--- a/sound/usb/line6/playback.c
+++ b/sound/usb/line6/playback.c
@@ -146,18 +146,20 @@ static int submit_audio_out_urb(struct snd_line6_pcm *line6pcm)
 	int index;
 	int i, urb_size, urb_frames;
 	int ret;
-	const int bytes_per_frame = line6pcm->properties->bytes_per_frame;
+	const int bytes_per_frame =
+		line6pcm->properties->bytes_per_channel *
+		line6pcm->properties->playback_hw.channels_max;
 	const int frame_increment =
 		line6pcm->properties->rates.rats[0].num_min;
 	const int frame_factor =
 		line6pcm->properties->rates.rats[0].den *
-		(USB_INTERVALS_PER_SECOND / LINE6_ISO_INTERVAL);
+		(line6pcm->line6->intervals_per_second / LINE6_ISO_INTERVAL);
 	struct urb *urb_out;
 
-	index =
-	    find_first_zero_bit(&line6pcm->out.active_urbs, LINE6_ISO_BUFFERS);
+	index = find_first_zero_bit(
+		&line6pcm->out.active_urbs, line6pcm->line6->iso_buffers);
 
-	if (index < 0 || index >= LINE6_ISO_BUFFERS) {
+	if (index < 0 || index >= line6pcm->line6->iso_buffers) {
 		dev_err(line6pcm->line6->ifcdev, "no free URB found\n");
 		return -EINVAL;
 	}
@@ -165,6 +167,7 @@ static int submit_audio_out_urb(struct snd_line6_pcm *line6pcm)
 	urb_out = line6pcm->out.urbs[index];
 	urb_size = 0;
 
+	/* TODO: this may not work for LINE6_ISO_PACKETS != 1 */
 	for (i = 0; i < LINE6_ISO_PACKETS; ++i) {
 		/* compute frame size for given sampling rate */
 		int fsize = 0;
@@ -178,9 +181,11 @@ static int submit_audio_out_urb(struct snd_line6_pcm *line6pcm)
 			line6pcm->out.count += frame_increment;
 			n = line6pcm->out.count / frame_factor;
 			line6pcm->out.count -= n * frame_factor;
-			fsize = n * bytes_per_frame;
+			fsize = n;
 		}
 
+		fsize *= bytes_per_frame;
+
 		fout->offset = urb_size;
 		fout->length = fsize;
 		urb_size += fsize;
@@ -195,7 +200,7 @@ static int submit_audio_out_urb(struct snd_line6_pcm *line6pcm)
 	urb_frames = urb_size / bytes_per_frame;
 	urb_out->transfer_buffer =
 	    line6pcm->out.buffer +
-	    index * LINE6_ISO_PACKETS * line6pcm->max_packet_size;
+	    index * LINE6_ISO_PACKETS * line6pcm->max_packet_size_out;
 	urb_out->transfer_buffer_length = urb_size;
 	urb_out->context = line6pcm;
 
@@ -286,7 +291,7 @@ int line6_submit_audio_out_all_urbs(struct snd_line6_pcm *line6pcm)
 {
 	int ret = 0, i;
 
-	for (i = 0; i < LINE6_ISO_BUFFERS; ++i) {
+	for (i = 0; i < line6pcm->line6->iso_buffers; ++i) {
 		ret = submit_audio_out_urb(line6pcm);
 		if (ret < 0)
 			break;
@@ -305,6 +310,9 @@ static void audio_out_callback(struct urb *urb)
 	struct snd_line6_pcm *line6pcm = (struct snd_line6_pcm *)urb->context;
 	struct snd_pcm_substream *substream =
 	    get_substream(line6pcm, SNDRV_PCM_STREAM_PLAYBACK);
+	const int bytes_per_frame =
+		line6pcm->properties->bytes_per_channel *
+		line6pcm->properties->playback_hw.channels_max;
 
 #if USE_CLEAR_BUFFER_WORKAROUND
 	memset(urb->transfer_buffer, 0, urb->transfer_buffer_length);
@@ -313,11 +321,11 @@ static void audio_out_callback(struct urb *urb)
 	line6pcm->out.last_frame = urb->start_frame;
 
 	/* find index of URB */
-	for (index = 0; index < LINE6_ISO_BUFFERS; index++)
+	for (index = 0; index < line6pcm->line6->iso_buffers; index++)
 		if (urb == line6pcm->out.urbs[index])
 			break;
 
-	if (index >= LINE6_ISO_BUFFERS)
+	if (index >= line6pcm->line6->iso_buffers)
 		return;		/* URB has been unlinked asynchronously */
 
 	for (i = 0; i < LINE6_ISO_PACKETS; i++)
@@ -329,7 +337,7 @@ static void audio_out_callback(struct urb *urb)
 		struct snd_pcm_runtime *runtime = substream->runtime;
 
 		line6pcm->out.pos_done +=
-		    length / line6pcm->properties->bytes_per_frame;
+		    length / bytes_per_frame;
 
 		if (line6pcm->out.pos_done >= runtime->buffer_size)
 			line6pcm->out.pos_done -= runtime->buffer_size;
@@ -401,8 +409,13 @@ int line6_create_audio_out_urbs(struct snd_line6_pcm *line6pcm)
 	struct usb_line6 *line6 = line6pcm->line6;
 	int i;
 
+	line6pcm->out.urbs = kzalloc(
+		sizeof(struct urb *) * line6->iso_buffers, GFP_KERNEL);
+	if (line6pcm->out.urbs == NULL)
+		return -ENOMEM;
+
 	/* create audio URBs and fill in constant values: */
-	for (i = 0; i < LINE6_ISO_BUFFERS; ++i) {
+	for (i = 0; i < line6->iso_buffers; ++i) {
 		struct urb *urb;
 
 		/* URB for audio out: */
diff --git a/sound/usb/line6/pod.c b/sound/usb/line6/pod.c
index 45dd348..36e7274 100644
--- a/sound/usb/line6/pod.c
+++ b/sound/usb/line6/pod.c
@@ -83,7 +83,6 @@ struct usb_line6_pod {
 };
 
 #define POD_SYSEX_CODE 3
-#define POD_BYTES_PER_FRAME 6	/* 24bit audio (stereo) */
 
 /* *INDENT-OFF* */
 
@@ -167,7 +166,7 @@ static struct line6_pcm_properties pod_pcm_properties = {
 	.rates = {
 			    .nrats = 1,
 			    .rats = &pod_ratden},
-	.bytes_per_frame = POD_BYTES_PER_FRAME
+	.bytes_per_channel = 3 /* SNDRV_PCM_FMTBIT_S24_3LE */
 };
 
 static const char pod_version_header[] = {
diff --git a/sound/usb/line6/podhd.c b/sound/usb/line6/podhd.c
index 63dcaef..4fc4789 100644
--- a/sound/usb/line6/podhd.c
+++ b/sound/usb/line6/podhd.c
@@ -25,8 +25,6 @@ enum {
 	LINE6_PODHD500_1,
 };
 
-#define PODHD_BYTES_PER_FRAME 6	/* 24bit audio (stereo) */
-
 static struct snd_ratden podhd_ratden = {
 	.num_min = 48000,
 	.num_max = 48000,
@@ -73,7 +71,7 @@ static struct line6_pcm_properties podhd_pcm_properties = {
 	.rates = {
 			    .nrats = 1,
 			    .rats = &podhd_ratden},
-	.bytes_per_frame = PODHD_BYTES_PER_FRAME
+	.bytes_per_channel = 3 /* 24bit audio (stereo) */
 };
 
 /*
diff --git a/sound/usb/line6/toneport.c b/sound/usb/line6/toneport.c
index 6d4c50c..da76e03 100644
--- a/sound/usb/line6/toneport.c
+++ b/sound/usb/line6/toneport.c
@@ -114,7 +114,7 @@ static struct line6_pcm_properties toneport_pcm_properties = {
 	.rates = {
 			    .nrats = 1,
 			    .rats = &toneport_ratden},
-	.bytes_per_frame = 4
+	.bytes_per_channel = 2
 };
 
 static const struct {
