diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index 94490d706013..eb459db511f8 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -440,22 +440,19 @@ static void snd_complete_urb(struct urb *urb)
 }
 
 /*
- * Get the existing endpoint object corresponding EP, iface and alt numbers
+ * Get the existing endpoint object corresponding EP
  * Returns NULL if not present.
- * Call inside chip->mutex locking for avoiding the race.
  */
 struct snd_usb_endpoint *
-snd_usb_get_endpoint(struct snd_usb_audio *chip,
-		     int ep_num, int iface, int altsetting)
+snd_usb_get_endpoint(struct snd_usb_audio *chip, int ep_num)
 {
 	struct snd_usb_endpoint *ep;
 
 	list_for_each_entry(ep, &chip->ep_list, list) {
-		if (ep->ep_num == ep_num &&
-		    ep->iface == iface &&
-		    ep->altsetting == altsetting)
+		if (ep->ep_num == ep_num)
 			return ep;
 	}
+
 	return NULL;
 }
 
@@ -466,14 +463,13 @@ snd_usb_get_endpoint(struct snd_usb_audio *chip,
  * snd_usb_add_endpoint: Add an endpoint to an USB audio chip
  *
  * @chip: The chip
- * @alts: The USB host interface
  * @ep_num: The number of the endpoint to use
- * @direction: SNDRV_PCM_STREAM_PLAYBACK or SNDRV_PCM_STREAM_CAPTURE
  * @type: SND_USB_ENDPOINT_TYPE_DATA or SND_USB_ENDPOINT_TYPE_SYNC
  *
  * If the requested endpoint has not been added to the given chip before,
- * a new instance is created. Otherwise, a pointer to the previoulsy
- * created instance is returned. In case of any error, NULL is returned.
+ * a new instance is created.
+ *
+ * Returns zero on success or a negative error code.
  *
  * New endpoints will be added to chip->ep_list and must be freed by
  * calling snd_usb_endpoint_free().
@@ -481,74 +477,59 @@ snd_usb_get_endpoint(struct snd_usb_audio *chip,
  * For SND_USB_ENDPOINT_TYPE_SYNC, the caller needs to guarantee that
  * bNumEndpoints > 1 beforehand.
  */
-struct snd_usb_endpoint *snd_usb_add_endpoint(struct snd_usb_audio *chip,
-					      struct usb_host_interface *alts,
-					      int ep_num, int direction, int type)
+int snd_usb_add_endpoint(struct snd_usb_audio *chip, int ep_num, int type)
 {
 	struct snd_usb_endpoint *ep;
-	int is_playback = direction == SNDRV_PCM_STREAM_PLAYBACK;
-
-	if (WARN_ON(!alts))
-		return NULL;
+	bool is_playback;
 
-	mutex_lock(&chip->mutex);
-
-	ep = snd_usb_get_endpoint(chip, ep_num,
-				  alts->desc.bInterfaceNumber,
-				  alts->desc.bAlternateSetting);
-	if (ep) {
-		usb_audio_dbg(ep->chip, "Re-using EP %x in iface %d,%d\n",
-			      ep_num, ep->iface, ep->altsetting);
-		goto __exit_unlock;
-	}
+	ep = snd_usb_get_endpoint(chip, ep_num);
+	if (ep)
+		return 0;
 
-	usb_audio_dbg(chip, "Creating new %s %s endpoint #%x\n",
-		      is_playback ? "playback" : "capture",
+	usb_audio_dbg(chip, "Creating new %s endpoint #%x\n",
 		      ep_type_name(type),
 		      ep_num);
-
 	ep = kzalloc(sizeof(*ep), GFP_KERNEL);
 	if (!ep)
-		goto __exit_unlock;
+		return -ENOMEM;
 
 	ep->chip = chip;
 	spin_lock_init(&ep->lock);
 	ep->type = type;
 	ep->ep_num = ep_num;
-	ep->iface = alts->desc.bInterfaceNumber;
-	ep->altsetting = alts->desc.bAlternateSetting;
 	INIT_LIST_HEAD(&ep->ready_playback_urbs);
-	ep_num &= USB_ENDPOINT_NUMBER_MASK;
 
+	is_playback = ((ep_num & USB_ENDPOINT_DIR_MASK) == USB_DIR_OUT);
+	ep_num &= USB_ENDPOINT_NUMBER_MASK;
 	if (is_playback)
 		ep->pipe = usb_sndisocpipe(chip->dev, ep_num);
 	else
 		ep->pipe = usb_rcvisocpipe(chip->dev, ep_num);
 
-	if (type == SND_USB_ENDPOINT_TYPE_SYNC) {
-		if (get_endpoint(alts, 1)->bLength >= USB_DT_ENDPOINT_AUDIO_SIZE &&
-		    get_endpoint(alts, 1)->bRefresh >= 1 &&
-		    get_endpoint(alts, 1)->bRefresh <= 9)
-			ep->syncinterval = get_endpoint(alts, 1)->bRefresh;
+	list_add_tail(&ep->list, &chip->ep_list);
+	return 0;
+}
+
+/* Set up syncinterval and maxsyncsize for a sync EP */
+void snd_usb_endpoint_set_syncinterval(struct snd_usb_audio *chip,
+				       struct snd_usb_endpoint *ep,
+				       struct usb_host_interface *alts)
+{
+	struct usb_endpoint_descriptor *desc = get_endpoint(alts, 1);
+
+	if (ep->type == SND_USB_ENDPOINT_TYPE_SYNC) {
+		if (desc->bLength >= USB_DT_ENDPOINT_AUDIO_SIZE &&
+		    desc->bRefresh >= 1 && desc->bRefresh <= 9)
+			ep->syncinterval = desc->bRefresh;
 		else if (snd_usb_get_speed(chip->dev) == USB_SPEED_FULL)
 			ep->syncinterval = 1;
-		else if (get_endpoint(alts, 1)->bInterval >= 1 &&
-			 get_endpoint(alts, 1)->bInterval <= 16)
-			ep->syncinterval = get_endpoint(alts, 1)->bInterval - 1;
+		else if (desc->bInterval >= 1 && desc->bInterval <= 16)
+			ep->syncinterval = desc->bInterval - 1;
 		else
 			ep->syncinterval = 3;
 
-		ep->syncmaxsize = le16_to_cpu(get_endpoint(alts, 1)->wMaxPacketSize);
+		ep->syncmaxsize = le16_to_cpu(desc->wMaxPacketSize);
 	}
-
-	list_add_tail(&ep->list, &chip->ep_list);
-
-	ep->is_implicit_feedback = 0;
-
-__exit_unlock:
-	mutex_unlock(&chip->mutex);
-
-	return ep;
 }
 
 /*
diff --git a/sound/usb/endpoint.h b/sound/usb/endpoint.h
index 61487095a766..76b6de7de991 100644
--- a/sound/usb/endpoint.h
+++ b/sound/usb/endpoint.h
@@ -6,12 +6,9 @@
 #define SND_USB_ENDPOINT_TYPE_SYNC     1
 
 struct snd_usb_endpoint *snd_usb_get_endpoint(struct snd_usb_audio *chip,
-					      int ep_num, int iface,
-					      int altsetting);
+					      int ep_num);
 
-struct snd_usb_endpoint *snd_usb_add_endpoint(struct snd_usb_audio *chip,
-					      struct usb_host_interface *alts,
-					      int ep_num, int direction, int type);
+int snd_usb_add_endpoint(struct snd_usb_audio *chip, int ep_num, int type);
 
 int snd_usb_endpoint_set_params(struct snd_usb_endpoint *ep,
 				snd_pcm_format_t pcm_format,
@@ -34,6 +31,9 @@ void snd_usb_endpoint_free(struct snd_usb_endpoint *ep);
 int snd_usb_endpoint_implicit_feedback_sink(struct snd_usb_endpoint *ep);
 int snd_usb_endpoint_slave_next_packet_size(struct snd_usb_endpoint *ep);
 int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep);
+void snd_usb_endpoint_set_syncinterval(struct snd_usb_audio *chip,
+				       struct snd_usb_endpoint *ep,
+				       struct usb_host_interface *alts);
 
 void snd_usb_handle_sync_urb(struct snd_usb_endpoint *ep,
 			     struct snd_usb_endpoint *sender,
diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index 8ae7d2fdba0d..03b1a02bcff4 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -585,11 +585,7 @@ static int set_sync_endpoint(struct snd_usb_substream *subs,
 	if (!alts)
 		return 0;
 
-	subs->sync_endpoint = snd_usb_add_endpoint(subs->stream->chip,
-						   alts, ep, !subs->direction,
-						   fmt->implicit_fb ?
-						   SND_USB_ENDPOINT_TYPE_DATA :
-						   SND_USB_ENDPOINT_TYPE_SYNC);
+	subs->sync_endpoint = snd_usb_get_endpoint(subs->stream->chip, ep);
 	if (!subs->sync_endpoint) {
 		if (is_playback &&
 		    (fmt->ep_attr & USB_ENDPOINT_SYNCTYPE) == USB_ENDPOINT_SYNC_NONE)
@@ -597,10 +593,14 @@ static int set_sync_endpoint(struct snd_usb_substream *subs,
 		return -EINVAL;
 	}
 
+	subs->sync_endpoint->iface = fmt->sync_iface;
+	subs->sync_endpoint->altsetting = fmt->sync_altsetting;
 	subs->sync_endpoint->is_implicit_feedback = fmt->implicit_fb;
 
 	subs->data_endpoint->sync_master = subs->sync_endpoint;
 
+	snd_usb_endpoint_set_syncinterval(subs->stream->chip, subs->sync_endpoint, alts);
+
 	if (!subs->sync_endpoint->use_count &&
 	    (subs->data_endpoint->iface != subs->sync_endpoint->iface ||
 	     subs->data_endpoint->altsetting != subs->sync_endpoint->altsetting)) {
@@ -641,8 +641,7 @@ static int set_format(struct snd_usb_substream *subs, struct audioformat *fmt)
 
 	/* shared EP with implicit fb */
 	if (fmt->implicit_fb && !subs->need_setup_fmt) {
-		ep = snd_usb_get_endpoint(subs->stream->chip, fmt->endpoint,
-					  fmt->iface, fmt->altsetting);
+		ep = snd_usb_get_endpoint(subs->stream->chip, fmt->endpoint);
 		if (ep && ep->use_count > 0)
 			goto add_data_ep;
 	}
@@ -688,12 +687,12 @@ static int set_format(struct snd_usb_substream *subs, struct audioformat *fmt)
  add_data_ep:
 	subs->interface = fmt->iface;
 	subs->altset_idx = fmt->altset_idx;
-	subs->data_endpoint = snd_usb_add_endpoint(subs->stream->chip,
-						   alts, fmt->endpoint, subs->direction,
-						   SND_USB_ENDPOINT_TYPE_DATA);
-
+	subs->data_endpoint = snd_usb_get_endpoint(subs->stream->chip,
+						   fmt->endpoint);
 	if (!subs->data_endpoint)
 		return -EINVAL;
+	subs->data_endpoint->iface = fmt->iface;
+	subs->data_endpoint->altsetting = fmt->altsetting;
 
 	err = set_sync_endpoint(subs, fmt);
 	if (err < 0)
@@ -1294,15 +1293,13 @@ static int apply_hw_constraint_from_sync(struct snd_pcm_runtime *runtime,
 
 	subs->fixed_hw = 0;
 	list_for_each_entry(fp, &subs->fmt_list, list) {
-		ep = snd_usb_get_endpoint(chip, fp->endpoint, fp->iface,
-					  fp->altsetting);
+		ep = snd_usb_get_endpoint(chip, fp->endpoint);
 		if (ep && ep->cur_rate)
 			goto found;
 		if (!fp->implicit_fb)
 			continue;
 		/* for the implicit fb, check the sync ep as well */
-		ep = snd_usb_get_endpoint(chip, fp->sync_ep, fp->sync_iface,
-					  fp->sync_altsetting);
+		ep = snd_usb_get_endpoint(chip, fp->sync_ep);
 		if (ep && ep->cur_rate)
 			goto found;
 	}
diff --git a/sound/usb/stream.c b/sound/usb/stream.c
index 7087ee2c8174..816fd3e5aada 100644
--- a/sound/usb/stream.c
+++ b/sound/usb/stream.c
@@ -1206,6 +1206,22 @@ static int __snd_usb_parse_audio_interface(struct snd_usb_audio *chip,
 			kfree(pd);
 			return err;
 		}
+
+		/* add endpoints */
+		err = snd_usb_add_endpoint(chip, fp->endpoint,
+					   SND_USB_ENDPOINT_TYPE_DATA);
+		if (err < 0)
+			return err;
+
+		if (fp->sync_ep) {
+			err = snd_usb_add_endpoint(chip, fp->sync_ep,
+						   fp->implicit_fb ?
+						   SND_USB_ENDPOINT_TYPE_DATA :
+						   SND_USB_ENDPOINT_TYPE_SYNC);
+			if (err < 0)
+				return err;
+		}
+
 		/* try to set the interface... */
 		usb_set_interface(chip->dev, iface_no, altno);
 		snd_usb_init_pitch(chip, iface_no, alts, fp);
