Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1893 insertions, 0 deletions

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
new file mode 100644
index 0000000000..8f65349a06
--- /dev/null
+++ b/sound/usb/endpoint.c
@@ -0,0 +1,1893 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ */
+
+#include <linux/gfp.h>
+#include <linux/init.h>
+#include <linux/ratelimit.h>
+#include <linux/usb.h>
+#include <linux/usb/audio.h>
+#include <linux/slab.h>
+
+#include <sound/core.h>
+#include <sound/pcm.h>
+#include <sound/pcm_params.h>
+
+#include "usbaudio.h"
+#include "helper.h"
+#include "card.h"
+#include "endpoint.h"
+#include "pcm.h"
+#include "clock.h"
+#include "quirks.h"
+
+enum {
+	EP_STATE_STOPPED,
+	EP_STATE_RUNNING,
+	EP_STATE_STOPPING,
+};
+
+/* interface refcounting */
+struct snd_usb_iface_ref {
+	unsigned char iface;
+	bool need_setup;
+	int opened;
+	int altset;
+	struct list_head list;
+};
+
+/* clock refcounting */
+struct snd_usb_clock_ref {
+	unsigned char clock;
+	atomic_t locked;
+	int opened;
+	int rate;
+	bool need_setup;
+	struct list_head list;
+};
+
+/*
+ * snd_usb_endpoint is a model that abstracts everything related to an
+ * USB endpoint and its streaming.
+ *
+ * There are functions to activate and deactivate the streaming URBs and
+ * optional callbacks to let the pcm logic handle the actual content of the
+ * packets for playback and record. Thus, the bus streaming and the audio
+ * handlers are fully decoupled.
+ *
+ * There are two different types of endpoints in audio applications.
+ *
+ * SND_USB_ENDPOINT_TYPE_DATA handles full audio data payload for both
+ * inbound and outbound traffic.
+ *
+ * SND_USB_ENDPOINT_TYPE_SYNC endpoints are for inbound traffic only and
+ * expect the payload to carry Q10.14 / Q16.16 formatted sync information
+ * (3 or 4 bytes).
+ *
+ * Each endpoint has to be configured prior to being used by calling
+ * snd_usb_endpoint_set_params().
+ *
+ * The model incorporates a reference counting, so that multiple users
+ * can call snd_usb_endpoint_start() and snd_usb_endpoint_stop(), and
+ * only the first user will effectively start the URBs, and only the last
+ * one to stop it will tear the URBs down again.
+ */
+
+/*
+ * convert a sampling rate into our full speed format (fs/1000 in Q16.16)
+ * this will overflow at approx 524 kHz
+ */
+static inline unsigned get_usb_full_speed_rate(unsigned int rate)
+{
+	return ((rate << 13) + 62) / 125;
+}
+
+/*
+ * convert a sampling rate into USB high speed format (fs/8000 in Q16.16)
+ * this will overflow at approx 4 MHz
+ */
+static inline unsigned get_usb_high_speed_rate(unsigned int rate)
+{
+	return ((rate << 10) + 62) / 125;
+}
+
+/*
+ * release a urb data
+ */
+static void release_urb_ctx(struct snd_urb_ctx *u)
+{
+	if (u->urb && u->buffer_size)
+		usb_free_coherent(u->ep->chip->dev, u->buffer_size,
+				  u->urb->transfer_buffer,
+				  u->urb->transfer_dma);
+	usb_free_urb(u->urb);
+	u->urb = NULL;
+	u->buffer_size = 0;
+}
+
+static const char *usb_error_string(int err)
+{
+	switch (err) {
+	case -ENODEV:
+		return "no device";
+	case -ENOENT:
+		return "endpoint not enabled";
+	case -EPIPE:
+		return "endpoint stalled";
+	case -ENOSPC:
+		return "not enough bandwidth";
+	case -ESHUTDOWN:
+		return "device disabled";
+	case -EHOSTUNREACH:
+		return "device suspended";
+	case -EINVAL:
+	case -EAGAIN:
+	case -EFBIG:
+	case -EMSGSIZE:
+		return "internal error";
+	default:
+		return "unknown error";
+	}
+}
+
+static inline bool ep_state_running(struct snd_usb_endpoint *ep)
+{
+	return atomic_read(&ep->state) == EP_STATE_RUNNING;
+}
+
+static inline bool ep_state_update(struct snd_usb_endpoint *ep, int old, int new)
+{
+	return atomic_try_cmpxchg(&ep->state, &old, new);
+}
+
+/**
+ * snd_usb_endpoint_implicit_feedback_sink: Report endpoint usage type
+ *
+ * @ep: The snd_usb_endpoint
+ *
+ * Determine whether an endpoint is driven by an implicit feedback
+ * data endpoint source.
+ */
+int snd_usb_endpoint_implicit_feedback_sink(struct snd_usb_endpoint *ep)
+{
+	return  ep->implicit_fb_sync && usb_pipeout(ep->pipe);
+}
+
+/*
+ * Return the number of samples to be sent in the next packet
+ * for streaming based on information derived from sync endpoints
+ *
+ * This won't be used for implicit feedback which takes the packet size
+ * returned from the sync source
+ */
+static int slave_next_packet_size(struct snd_usb_endpoint *ep,
+				  unsigned int avail)
+{
+	unsigned long flags;
+	unsigned int phase;
+	int ret;
+
+	if (ep->fill_max)
+		return ep->maxframesize;
+
+	spin_lock_irqsave(&ep->lock, flags);
+	phase = (ep->phase & 0xffff) + (ep->freqm << ep->datainterval);
+	ret = min(phase >> 16, ep->maxframesize);
+	if (avail && ret >= avail)
+		ret = -EAGAIN;
+	else
+		ep->phase = phase;
+	spin_unlock_irqrestore(&ep->lock, flags);
+
+	return ret;
+}
+
+/*
+ * Return the number of samples to be sent in the next packet
+ * for adaptive and synchronous endpoints
+ */
+static int next_packet_size(struct snd_usb_endpoint *ep, unsigned int avail)
+{
+	unsigned int sample_accum;
+	int ret;
+
+	if (ep->fill_max)
+		return ep->maxframesize;
+
+	sample_accum = ep->sample_accum + ep->sample_rem;
+	if (sample_accum >= ep->pps) {
+		sample_accum -= ep->pps;
+		ret = ep->packsize[1];
+	} else {
+		ret = ep->packsize[0];
+	}
+	if (avail && ret >= avail)
+		ret = -EAGAIN;
+	else
+		ep->sample_accum = sample_accum;
+
+	return ret;
+}
+
+/*
+ * snd_usb_endpoint_next_packet_size: Return the number of samples to be sent
+ * in the next packet
+ *
+ * If the size is equal or exceeds @avail, don't proceed but return -EAGAIN
+ * Exception: @avail = 0 for skipping the check.
+ */
+int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep,
+				      struct snd_urb_ctx *ctx, int idx,
+				      unsigned int avail)
+{
+	unsigned int packet;
+
+	packet = ctx->packet_size[idx];
+	if (packet) {
+		if (avail && packet >= avail)
+			return -EAGAIN;
+		return packet;
+	}
+
+	if (ep->sync_source)
+		return slave_next_packet_size(ep, avail);
+	else
+		return next_packet_size(ep, avail);
+}
+
+static void call_retire_callback(struct snd_usb_endpoint *ep,
+				 struct urb *urb)
+{
+	struct snd_usb_substream *data_subs;
+
+	data_subs = READ_ONCE(ep->data_subs);
+	if (data_subs && ep->retire_data_urb)
+		ep->retire_data_urb(data_subs, urb);
+}
+
+static void retire_outbound_urb(struct snd_usb_endpoint *ep,
+				struct snd_urb_ctx *urb_ctx)
+{
+	call_retire_callback(ep, urb_ctx->urb);
+}
+
+static void snd_usb_handle_sync_urb(struct snd_usb_endpoint *ep,
+				    struct snd_usb_endpoint *sender,
+				    const struct urb *urb);
+
+static void retire_inbound_urb(struct snd_usb_endpoint *ep,
+			       struct snd_urb_ctx *urb_ctx)
+{
+	struct urb *urb = urb_ctx->urb;
+	struct snd_usb_endpoint *sync_sink;
+
+	if (unlikely(ep->skip_packets > 0)) {
+		ep->skip_packets--;
+		return;
+	}
+
+	sync_sink = READ_ONCE(ep->sync_sink);
+	if (sync_sink)
+		snd_usb_handle_sync_urb(sync_sink, ep, urb);
+
+	call_retire_callback(ep, urb);
+}
+
+static inline bool has_tx_length_quirk(struct snd_usb_audio *chip)
+{
+	return chip->quirk_flags & QUIRK_FLAG_TX_LENGTH;
+}
+
+static void prepare_silent_urb(struct snd_usb_endpoint *ep,
+			       struct snd_urb_ctx *ctx)
+{
+	struct urb *urb = ctx->urb;
+	unsigned int offs = 0;
+	unsigned int extra = 0;
+	__le32 packet_length;
+	int i;
+
+	/* For tx_length_quirk, put packet length at start of packet */
+	if (has_tx_length_quirk(ep->chip))
+		extra = sizeof(packet_length);
+
+	for (i = 0; i < ctx->packets; ++i) {
+		unsigned int offset;
+		unsigned int length;
+		int counts;
+
+		counts = snd_usb_endpoint_next_packet_size(ep, ctx, i, 0);
+		length = counts * ep->stride; /* number of silent bytes */
+		offset = offs * ep->stride + extra * i;
+		urb->iso_frame_desc[i].offset = offset;
+		urb->iso_frame_desc[i].length = length + extra;
+		if (extra) {
+			packet_length = cpu_to_le32(length);
+			memcpy(urb->transfer_buffer + offset,
+			       &packet_length, sizeof(packet_length));
+		}
+		memset(urb->transfer_buffer + offset + extra,
+		       ep->silence_value, length);
+		offs += counts;
+	}
+
+	urb->number_of_packets = ctx->packets;
+	urb->transfer_buffer_length = offs * ep->stride + ctx->packets * extra;
+	ctx->queued = 0;
+}
+
+/*
+ * Prepare a PLAYBACK urb for submission to the bus.
+ */
+static int prepare_outbound_urb(struct snd_usb_endpoint *ep,
+				struct snd_urb_ctx *ctx,
+				bool in_stream_lock)
+{
+	struct urb *urb = ctx->urb;
+	unsigned char *cp = urb->transfer_buffer;
+	struct snd_usb_substream *data_subs;
+
+	urb->dev = ep->chip->dev; /* we need to set this at each time */
+
+	switch (ep->type) {
+	case SND_USB_ENDPOINT_TYPE_DATA:
+		data_subs = READ_ONCE(ep->data_subs);
+		if (data_subs && ep->prepare_data_urb)
+			return ep->prepare_data_urb(data_subs, urb, in_stream_lock);
+		/* no data provider, so send silence */
+		prepare_silent_urb(ep, ctx);
+		break;
+
+	case SND_USB_ENDPOINT_TYPE_SYNC:
+		if (snd_usb_get_speed(ep->chip->dev) >= USB_SPEED_HIGH) {
+			/*
+			 * fill the length and offset of each urb descriptor.
+			 * the fixed 12.13 frequency is passed as 16.16 through the pipe.
+			 */
+			urb->iso_frame_desc[0].length = 4;
+			urb->iso_frame_desc[0].offset = 0;
+			cp[0] = ep->freqn;
+			cp[1] = ep->freqn >> 8;
+			cp[2] = ep->freqn >> 16;
+			cp[3] = ep->freqn >> 24;
+		} else {
+			/*
+			 * fill the length and offset of each urb descriptor.
+			 * the fixed 10.14 frequency is passed through the pipe.
+			 */
+			urb->iso_frame_desc[0].length = 3;
+			urb->iso_frame_desc[0].offset = 0;
+			cp[0] = ep->freqn >> 2;
+			cp[1] = ep->freqn >> 10;
+			cp[2] = ep->freqn >> 18;
+		}
+
+		break;
+	}
+	return 0;
+}
+
+/*
+ * Prepare a CAPTURE or SYNC urb for submission to the bus.
+ */
+static int prepare_inbound_urb(struct snd_usb_endpoint *ep,
+			       struct snd_urb_ctx *urb_ctx)
+{
+	int i, offs;
+	struct urb *urb = urb_ctx->urb;
+
+	urb->dev = ep->chip->dev; /* we need to set this at each time */
+
+	switch (ep->type) {
+	case SND_USB_ENDPOINT_TYPE_DATA:
+		offs = 0;
+		for (i = 0; i < urb_ctx->packets; i++) {
+			urb->iso_frame_desc[i].offset = offs;
+			urb->iso_frame_desc[i].length = ep->curpacksize;
+			offs += ep->curpacksize;
+		}
+
+		urb->transfer_buffer_length = offs;
+		urb->number_of_packets = urb_ctx->packets;
+		break;
+
+	case SND_USB_ENDPOINT_TYPE_SYNC:
+		urb->iso_frame_desc[0].length = min(4u, ep->syncmaxsize);
+		urb->iso_frame_desc[0].offset = 0;
+		break;
+	}
+	return 0;
+}
+
+/* notify an error as XRUN to the assigned PCM data substream */
+static void notify_xrun(struct snd_usb_endpoint *ep)
+{
+	struct snd_usb_substream *data_subs;
+
+	data_subs = READ_ONCE(ep->data_subs);
+	if (data_subs && data_subs->pcm_substream)
+		snd_pcm_stop_xrun(data_subs->pcm_substream);
+}
+
+static struct snd_usb_packet_info *
+next_packet_fifo_enqueue(struct snd_usb_endpoint *ep)
+{
+	struct snd_usb_packet_info *p;
+
+	p = ep->next_packet + (ep->next_packet_head + ep->next_packet_queued) %
+		ARRAY_SIZE(ep->next_packet);
+	ep->next_packet_queued++;
+	return p;
+}
+
+static struct snd_usb_packet_info *
+next_packet_fifo_dequeue(struct snd_usb_endpoint *ep)
+{
+	struct snd_usb_packet_info *p;
+
+	p = ep->next_packet + ep->next_packet_head;
+	ep->next_packet_head++;
+	ep->next_packet_head %= ARRAY_SIZE(ep->next_packet);
+	ep->next_packet_queued--;
+	return p;
+}
+
+static void push_back_to_ready_list(struct snd_usb_endpoint *ep,
+				    struct snd_urb_ctx *ctx)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&ep->lock, flags);
+	list_add_tail(&ctx->ready_list, &ep->ready_playback_urbs);
+	spin_unlock_irqrestore(&ep->lock, flags);
+}
+
+/*
+ * Send output urbs that have been prepared previously. URBs are dequeued
+ * from ep->ready_playback_urbs and in case there aren't any available
+ * or there are no packets that have been prepared, this function does
+ * nothing.
+ *
+ * The reason why the functionality of sending and preparing URBs is separated
+ * is that host controllers don't guarantee the order in which they return
+ * inbound and outbound packets to their submitters.
+ *
+ * This function is used both for implicit feedback endpoints and in low-
+ * latency playback mode.
+ */
+int snd_usb_queue_pending_output_urbs(struct snd_usb_endpoint *ep,
+				      bool in_stream_lock)
+{
+	bool implicit_fb = snd_usb_endpoint_implicit_feedback_sink(ep);
+
+	while (ep_state_running(ep)) {
+
+		unsigned long flags;
+		struct snd_usb_packet_info *packet;
+		struct snd_urb_ctx *ctx = NULL;
+		int err, i;
+
+		spin_lock_irqsave(&ep->lock, flags);
+		if ((!implicit_fb || ep->next_packet_queued > 0) &&
+		    !list_empty(&ep->ready_playback_urbs)) {
+			/* take URB out of FIFO */
+			ctx = list_first_entry(&ep->ready_playback_urbs,
+					       struct snd_urb_ctx, ready_list);
+			list_del_init(&ctx->ready_list);
+			if (implicit_fb)
+				packet = next_packet_fifo_dequeue(ep);
+		}
+		spin_unlock_irqrestore(&ep->lock, flags);
+
+		if (ctx == NULL)
+			break;
+
+		/* copy over the length information */
+		if (implicit_fb) {
+			for (i = 0; i < packet->packets; i++)
+				ctx->packet_size[i] = packet->packet_size[i];
+		}
+
+		/* call the data handler to fill in playback data */
+		err = prepare_outbound_urb(ep, ctx, in_stream_lock);
+		/* can be stopped during prepare callback */
+		if (unlikely(!ep_state_running(ep)))
+			break;
+		if (err < 0) {
+			/* push back to ready list again for -EAGAIN */
+			if (err == -EAGAIN) {
+				push_back_to_ready_list(ep, ctx);
+				break;
+			}
+
+			if (!in_stream_lock)
+				notify_xrun(ep);
+			return -EPIPE;
+		}
+
+		if (!atomic_read(&ep->chip->shutdown))
+			err = usb_submit_urb(ctx->urb, GFP_ATOMIC);
+		else
+			err = -ENODEV;
+		if (err < 0) {
+			if (!atomic_read(&ep->chip->shutdown)) {
+				usb_audio_err(ep->chip,
+					      "Unable to submit urb #%d: %d at %s\n",
+					      ctx->index, err, __func__);
+				if (!in_stream_lock)
+					notify_xrun(ep);
+			}
+			return -EPIPE;
+		}
+
+		set_bit(ctx->index, &ep->active_mask);
+		atomic_inc(&ep->submitted_urbs);
+	}
+
+	return 0;
+}
+
+/*
+ * complete callback for urbs
+ */
+static void snd_complete_urb(struct urb *urb)
+{
+	struct snd_urb_ctx *ctx = urb->context;
+	struct snd_usb_endpoint *ep = ctx->ep;
+	int err;
+
+	if (unlikely(urb->status == -ENOENT ||		/* unlinked */
+		     urb->status == -ENODEV ||		/* device removed */
+		     urb->status == -ECONNRESET ||	/* unlinked */
+		     urb->status == -ESHUTDOWN))	/* device disabled */
+		goto exit_clear;
+	/* device disconnected */
+	if (unlikely(atomic_read(&ep->chip->shutdown)))
+		goto exit_clear;
+
+	if (unlikely(!ep_state_running(ep)))
+		goto exit_clear;
+
+	if (usb_pipeout(ep->pipe)) {
+		retire_outbound_urb(ep, ctx);
+		/* can be stopped during retire callback */
+		if (unlikely(!ep_state_running(ep)))
+			goto exit_clear;
+
+		/* in low-latency and implicit-feedback modes, push back the
+		 * URB to ready list at first, then process as much as possible
+		 */
+		if (ep->lowlatency_playback ||
+		     snd_usb_endpoint_implicit_feedback_sink(ep)) {
+			push_back_to_ready_list(ep, ctx);
+			clear_bit(ctx->index, &ep->active_mask);
+			snd_usb_queue_pending_output_urbs(ep, false);
+			atomic_dec(&ep->submitted_urbs); /* decrement at last */
+			return;
+		}
+
+		/* in non-lowlatency mode, no error handling for prepare */
+		prepare_outbound_urb(ep, ctx, false);
+		/* can be stopped during prepare callback */
+		if (unlikely(!ep_state_running(ep)))
+			goto exit_clear;
+	} else {
+		retire_inbound_urb(ep, ctx);
+		/* can be stopped during retire callback */
+		if (unlikely(!ep_state_running(ep)))
+			goto exit_clear;
+
+		prepare_inbound_urb(ep, ctx);
+	}
+
+	if (!atomic_read(&ep->chip->shutdown))
+		err = usb_submit_urb(urb, GFP_ATOMIC);
+	else
+		err = -ENODEV;
+	if (err == 0)
+		return;
+
+	if (!atomic_read(&ep->chip->shutdown)) {
+		usb_audio_err(ep->chip, "cannot submit urb (err = %d)\n", err);
+		notify_xrun(ep);
+	}
+
+exit_clear:
+	clear_bit(ctx->index, &ep->active_mask);
+	atomic_dec(&ep->submitted_urbs);
+}
+
+/*
+ * Find or create a refcount object for the given interface
+ *
+ * The objects are released altogether in snd_usb_endpoint_free_all()
+ */
+static struct snd_usb_iface_ref *
+iface_ref_find(struct snd_usb_audio *chip, int iface)
+{
+	struct snd_usb_iface_ref *ip;
+
+	list_for_each_entry(ip, &chip->iface_ref_list, list)
+		if (ip->iface == iface)
+			return ip;
+
+	ip = kzalloc(sizeof(*ip), GFP_KERNEL);
+	if (!ip)
+		return NULL;
+	ip->iface = iface;
+	list_add_tail(&ip->list, &chip->iface_ref_list);
+	return ip;
+}
+
+/* Similarly, a refcount object for clock */
+static struct snd_usb_clock_ref *
+clock_ref_find(struct snd_usb_audio *chip, int clock)
+{
+	struct snd_usb_clock_ref *ref;
+
+	list_for_each_entry(ref, &chip->clock_ref_list, list)
+		if (ref->clock == clock)
+			return ref;
+
+	ref = kzalloc(sizeof(*ref), GFP_KERNEL);
+	if (!ref)
+		return NULL;
+	ref->clock = clock;
+	atomic_set(&ref->locked, 0);
+	list_add_tail(&ref->list, &chip->clock_ref_list);
+	return ref;
+}
+
+/*
+ * Get the existing endpoint object corresponding EP
+ * Returns NULL if not present.
+ */
+struct snd_usb_endpoint *
+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)
+			return ep;
+	}
+
+	return NULL;
+}
+
+#define ep_type_name(type) \
+	(type == SND_USB_ENDPOINT_TYPE_DATA ? "data" : "sync")
+
+/**
+ * snd_usb_add_endpoint: Add an endpoint to an USB audio chip
+ *
+ * @chip: The chip
+ * @ep_num: The number of the endpoint to use
+ * @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.
+ *
+ * Returns zero on success or a negative error code.
+ *
+ * New endpoints will be added to chip->ep_list and freed by
+ * calling snd_usb_endpoint_free_all().
+ *
+ * For SND_USB_ENDPOINT_TYPE_SYNC, the caller needs to guarantee that
+ * bNumEndpoints > 1 beforehand.
+ */
+int snd_usb_add_endpoint(struct snd_usb_audio *chip, int ep_num, int type)
+{
+	struct snd_usb_endpoint *ep;
+	bool is_playback;
+
+	ep = snd_usb_get_endpoint(chip, ep_num);
+	if (ep)
+		return 0;
+
+	usb_audio_dbg(chip, "Creating new %s endpoint #%x\n",
+		      ep_type_name(type),
+		      ep_num);
+	ep = kzalloc(sizeof(*ep), GFP_KERNEL);
+	if (!ep)
+		return -ENOMEM;
+
+	ep->chip = chip;
+	spin_lock_init(&ep->lock);
+	ep->type = type;
+	ep->ep_num = ep_num;
+	INIT_LIST_HEAD(&ep->ready_playback_urbs);
+	atomic_set(&ep->submitted_urbs, 0);
+
+	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);
+
+	list_add_tail(&ep->list, &chip->ep_list);
+	return 0;
+}
+
+/* Set up syncinterval and maxsyncsize for a sync EP */
+static void endpoint_set_syncinterval(struct snd_usb_audio *chip,
+				      struct snd_usb_endpoint *ep)
+{
+	struct usb_host_interface *alts;
+	struct usb_endpoint_descriptor *desc;
+
+	alts = snd_usb_get_host_interface(chip, ep->iface, ep->altsetting);
+	if (!alts)
+		return;
+
+	desc = get_endpoint(alts, ep->ep_idx);
+	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 (desc->bInterval >= 1 && desc->bInterval <= 16)
+		ep->syncinterval = desc->bInterval - 1;
+	else
+		ep->syncinterval = 3;
+
+	ep->syncmaxsize = le16_to_cpu(desc->wMaxPacketSize);
+}
+
+static bool endpoint_compatible(struct snd_usb_endpoint *ep,
+				const struct audioformat *fp,
+				const struct snd_pcm_hw_params *params)
+{
+	if (!ep->opened)
+		return false;
+	if (ep->cur_audiofmt != fp)
+		return false;
+	if (ep->cur_rate != params_rate(params) ||
+	    ep->cur_format != params_format(params) ||
+	    ep->cur_period_frames != params_period_size(params) ||
+	    ep->cur_buffer_periods != params_periods(params))
+		return false;
+	return true;
+}
+
+/*
+ * Check whether the given fp and hw params are compatible with the current
+ * setup of the target EP for implicit feedback sync
+ */
+bool snd_usb_endpoint_compatible(struct snd_usb_audio *chip,
+				 struct snd_usb_endpoint *ep,
+				 const struct audioformat *fp,
+				 const struct snd_pcm_hw_params *params)
+{
+	bool ret;
+
+	mutex_lock(&chip->mutex);
+	ret = endpoint_compatible(ep, fp, params);
+	mutex_unlock(&chip->mutex);
+	return ret;
+}
+
+/*
+ * snd_usb_endpoint_open: Open the endpoint
+ *
+ * Called from hw_params to assign the endpoint to the substream.
+ * It's reference-counted, and only the first opener is allowed to set up
+ * arbitrary parameters.  The later opener must be compatible with the
+ * former opened parameters.
+ * The endpoint needs to be closed via snd_usb_endpoint_close() later.
+ *
+ * Note that this function doesn't configure the endpoint.  The substream
+ * needs to set it up later via snd_usb_endpoint_set_params() and
+ * snd_usb_endpoint_prepare().
+ */
+struct snd_usb_endpoint *
+snd_usb_endpoint_open(struct snd_usb_audio *chip,
+		      const struct audioformat *fp,
+		      const struct snd_pcm_hw_params *params,
+		      bool is_sync_ep,
+		      bool fixed_rate)
+{
+	struct snd_usb_endpoint *ep;
+	int ep_num = is_sync_ep ? fp->sync_ep : fp->endpoint;
+
+	mutex_lock(&chip->mutex);
+	ep = snd_usb_get_endpoint(chip, ep_num);
+	if (!ep) {
+		usb_audio_err(chip, "Cannot find EP 0x%x to open\n", ep_num);
+		goto unlock;
+	}
+
+	if (!ep->opened) {
+		if (is_sync_ep) {
+			ep->iface = fp->sync_iface;
+			ep->altsetting = fp->sync_altsetting;
+			ep->ep_idx = fp->sync_ep_idx;
+		} else {
+			ep->iface = fp->iface;
+			ep->altsetting = fp->altsetting;
+			ep->ep_idx = fp->ep_idx;
+		}
+		usb_audio_dbg(chip, "Open EP 0x%x, iface=%d:%d, idx=%d\n",
+			      ep_num, ep->iface, ep->altsetting, ep->ep_idx);
+
+		ep->iface_ref = iface_ref_find(chip, ep->iface);
+		if (!ep->iface_ref) {
+			ep = NULL;
+			goto unlock;
+		}
+
+		if (fp->protocol != UAC_VERSION_1) {
+			ep->clock_ref = clock_ref_find(chip, fp->clock);
+			if (!ep->clock_ref) {
+				ep = NULL;
+				goto unlock;
+			}
+			ep->clock_ref->opened++;
+		}
+
+		ep->cur_audiofmt = fp;
+		ep->cur_channels = fp->channels;
+		ep->cur_rate = params_rate(params);
+		ep->cur_format = params_format(params);
+		ep->cur_frame_bytes = snd_pcm_format_physical_width(ep->cur_format) *
+			ep->cur_channels / 8;
+		ep->cur_period_frames = params_period_size(params);
+		ep->cur_period_bytes = ep->cur_period_frames * ep->cur_frame_bytes;
+		ep->cur_buffer_periods = params_periods(params);
+
+		if (ep->type == SND_USB_ENDPOINT_TYPE_SYNC)
+			endpoint_set_syncinterval(chip, ep);
+
+		ep->implicit_fb_sync = fp->implicit_fb;
+		ep->need_setup = true;
+		ep->need_prepare = true;
+		ep->fixed_rate = fixed_rate;
+
+		usb_audio_dbg(chip, "  channels=%d, rate=%d, format=%s, period_bytes=%d, periods=%d, implicit_fb=%d\n",
+			      ep->cur_channels, ep->cur_rate,
+			      snd_pcm_format_name(ep->cur_format),
+			      ep->cur_period_bytes, ep->cur_buffer_periods,
+			      ep->implicit_fb_sync);
+
+	} else {
+		if (WARN_ON(!ep->iface_ref)) {
+			ep = NULL;
+			goto unlock;
+		}
+
+		if (!endpoint_compatible(ep, fp, params)) {
+			usb_audio_err(chip, "Incompatible EP setup for 0x%x\n",
+				      ep_num);
+			ep = NULL;
+			goto unlock;
+		}
+
+		usb_audio_dbg(chip, "Reopened EP 0x%x (count %d)\n",
+			      ep_num, ep->opened);
+	}
+
+	if (!ep->iface_ref->opened++)
+		ep->iface_ref->need_setup = true;
+
+	ep->opened++;
+
+ unlock:
+	mutex_unlock(&chip->mutex);
+	return ep;
+}
+
+/*
+ * snd_usb_endpoint_set_sync: Link data and sync endpoints
+ *
+ * Pass NULL to sync_ep to unlink again
+ */
+void snd_usb_endpoint_set_sync(struct snd_usb_audio *chip,
+			       struct snd_usb_endpoint *data_ep,
+			       struct snd_usb_endpoint *sync_ep)
+{
+	data_ep->sync_source = sync_ep;
+}
+
+/*
+ * Set data endpoint callbacks and the assigned data stream
+ *
+ * Called at PCM trigger and cleanups.
+ * Pass NULL to deactivate each callback.
+ */
+void snd_usb_endpoint_set_callback(struct snd_usb_endpoint *ep,
+				   int (*prepare)(struct snd_usb_substream *subs,
+						  struct urb *urb,
+						  bool in_stream_lock),
+				   void (*retire)(struct snd_usb_substream *subs,
+						  struct urb *urb),
+				   struct snd_usb_substream *data_subs)
+{
+	ep->prepare_data_urb = prepare;
+	ep->retire_data_urb = retire;
+	if (data_subs)
+		ep->lowlatency_playback = data_subs->lowlatency_playback;
+	else
+		ep->lowlatency_playback = false;
+	WRITE_ONCE(ep->data_subs, data_subs);
+}
+
+static int endpoint_set_interface(struct snd_usb_audio *chip,
+				  struct snd_usb_endpoint *ep,
+				  bool set)
+{
+	int altset = set ? ep->altsetting : 0;
+	int err;
+
+	if (ep->iface_ref->altset == altset)
+		return 0;
+
+	usb_audio_dbg(chip, "Setting usb interface %d:%d for EP 0x%x\n",
+		      ep->iface, altset, ep->ep_num);
+	err = usb_set_interface(chip->dev, ep->iface, altset);
+	if (err < 0) {
+		usb_audio_err_ratelimited(
+			chip, "%d:%d: usb_set_interface failed (%d)\n",
+			ep->iface, altset, err);
+		return err;
+	}
+
+	if (chip->quirk_flags & QUIRK_FLAG_IFACE_DELAY)
+		msleep(50);
+	ep->iface_ref->altset = altset;
+	return 0;
+}
+
+/*
+ * snd_usb_endpoint_close: Close the endpoint
+ *
+ * Unreference the already opened endpoint via snd_usb_endpoint_open().
+ */
+void snd_usb_endpoint_close(struct snd_usb_audio *chip,
+			    struct snd_usb_endpoint *ep)
+{
+	mutex_lock(&chip->mutex);
+	usb_audio_dbg(chip, "Closing EP 0x%x (count %d)\n",
+		      ep->ep_num, ep->opened);
+
+	if (!--ep->iface_ref->opened &&
+		!(chip->quirk_flags & QUIRK_FLAG_IFACE_SKIP_CLOSE))
+		endpoint_set_interface(chip, ep, false);
+
+	if (!--ep->opened) {
+		if (ep->clock_ref) {
+			if (!--ep->clock_ref->opened)
+				ep->clock_ref->rate = 0;
+		}
+		ep->iface = 0;
+		ep->altsetting = 0;
+		ep->cur_audiofmt = NULL;
+		ep->cur_rate = 0;
+		ep->iface_ref = NULL;
+		ep->clock_ref = NULL;
+		usb_audio_dbg(chip, "EP 0x%x closed\n", ep->ep_num);
+	}
+	mutex_unlock(&chip->mutex);
+}
+
+/* Prepare for suspening EP, called from the main suspend handler */
+void snd_usb_endpoint_suspend(struct snd_usb_endpoint *ep)
+{
+	ep->need_prepare = true;
+	if (ep->iface_ref)
+		ep->iface_ref->need_setup = true;
+	if (ep->clock_ref)
+		ep->clock_ref->rate = 0;
+}
+
+/*
+ *  wait until all urbs are processed.
+ */
+static int wait_clear_urbs(struct snd_usb_endpoint *ep)
+{
+	unsigned long end_time = jiffies + msecs_to_jiffies(1000);
+	int alive;
+
+	if (atomic_read(&ep->state) != EP_STATE_STOPPING)
+		return 0;
+
+	do {
+		alive = atomic_read(&ep->submitted_urbs);
+		if (!alive)
+			break;
+
+		schedule_timeout_uninterruptible(1);
+	} while (time_before(jiffies, end_time));
+
+	if (alive)
+		usb_audio_err(ep->chip,
+			"timeout: still %d active urbs on EP #%x\n",
+			alive, ep->ep_num);
+
+	if (ep_state_update(ep, EP_STATE_STOPPING, EP_STATE_STOPPED)) {
+		ep->sync_sink = NULL;
+		snd_usb_endpoint_set_callback(ep, NULL, NULL, NULL);
+	}
+
+	return 0;
+}
+
+/* sync the pending stop operation;
+ * this function itself doesn't trigger the stop operation
+ */
+void snd_usb_endpoint_sync_pending_stop(struct snd_usb_endpoint *ep)
+{
+	if (ep)
+		wait_clear_urbs(ep);
+}
+
+/*
+ * Stop active urbs
+ *
+ * This function moves the EP to STOPPING state if it's being RUNNING.
+ */
+static int stop_urbs(struct snd_usb_endpoint *ep, bool force, bool keep_pending)
+{
+	unsigned int i;
+	unsigned long flags;
+
+	if (!force && atomic_read(&ep->running))
+		return -EBUSY;
+
+	if (!ep_state_update(ep, EP_STATE_RUNNING, EP_STATE_STOPPING))
+		return 0;
+
+	spin_lock_irqsave(&ep->lock, flags);
+	INIT_LIST_HEAD(&ep->ready_playback_urbs);
+	ep->next_packet_head = 0;
+	ep->next_packet_queued = 0;
+	spin_unlock_irqrestore(&ep->lock, flags);
+
+	if (keep_pending)
+		return 0;
+
+	for (i = 0; i < ep->nurbs; i++) {
+		if (test_bit(i, &ep->active_mask)) {
+			if (!test_and_set_bit(i, &ep->unlink_mask)) {
+				struct urb *u = ep->urb[i].urb;
+				usb_unlink_urb(u);
+			}
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * release an endpoint's urbs
+ */
+static int release_urbs(struct snd_usb_endpoint *ep, bool force)
+{
+	int i, err;
+
+	/* route incoming urbs to nirvana */
+	snd_usb_endpoint_set_callback(ep, NULL, NULL, NULL);
+
+	/* stop and unlink urbs */
+	err = stop_urbs(ep, force, false);
+	if (err)
+		return err;
+
+	wait_clear_urbs(ep);
+
+	for (i = 0; i < ep->nurbs; i++)
+		release_urb_ctx(&ep->urb[i]);
+
+	usb_free_coherent(ep->chip->dev, SYNC_URBS * 4,
+			  ep->syncbuf, ep->sync_dma);
+
+	ep->syncbuf = NULL;
+	ep->nurbs = 0;
+	return 0;
+}
+
+/*
+ * configure a data endpoint
+ */
+static int data_ep_set_params(struct snd_usb_endpoint *ep)
+{
+	struct snd_usb_audio *chip = ep->chip;
+	unsigned int maxsize, minsize, packs_per_ms, max_packs_per_urb;
+	unsigned int max_packs_per_period, urbs_per_period, urb_packs;
+	unsigned int max_urbs, i;
+	const struct audioformat *fmt = ep->cur_audiofmt;
+	int frame_bits = ep->cur_frame_bytes * 8;
+	int tx_length_quirk = (has_tx_length_quirk(chip) &&
+			       usb_pipeout(ep->pipe));
+
+	usb_audio_dbg(chip, "Setting params for data EP 0x%x, pipe 0x%x\n",
+		      ep->ep_num, ep->pipe);
+
+	if (ep->cur_format == SNDRV_PCM_FORMAT_DSD_U16_LE && fmt->dsd_dop) {
+		/*
+		 * When operating in DSD DOP mode, the size of a sample frame
+		 * in hardware differs from the actual physical format width
+		 * because we need to make room for the DOP markers.
+		 */
+		frame_bits += ep->cur_channels << 3;
+	}
+
+	ep->datainterval = fmt->datainterval;
+	ep->stride = frame_bits >> 3;
+
+	switch (ep->cur_format) {
+	case SNDRV_PCM_FORMAT_U8:
+		ep->silence_value = 0x80;
+		break;
+	case SNDRV_PCM_FORMAT_DSD_U8:
+	case SNDRV_PCM_FORMAT_DSD_U16_LE:
+	case SNDRV_PCM_FORMAT_DSD_U32_LE:
+	case SNDRV_PCM_FORMAT_DSD_U16_BE:
+	case SNDRV_PCM_FORMAT_DSD_U32_BE:
+		ep->silence_value = 0x69;
+		break;
+	default:
+		ep->silence_value = 0;
+	}
+
+	/* assume max. frequency is 50% higher than nominal */
+	ep->freqmax = ep->freqn + (ep->freqn >> 1);
+	/* Round up freqmax to nearest integer in order to calculate maximum
+	 * packet size, which must represent a whole number of frames.
+	 * This is accomplished by adding 0x0.ffff before converting the
+	 * Q16.16 format into integer.
+	 * In order to accurately calculate the maximum packet size when
+	 * the data interval is more than 1 (i.e. ep->datainterval > 0),
+	 * multiply by the data interval prior to rounding. For instance,
+	 * a freqmax of 41 kHz will result in a max packet size of 6 (5.125)
+	 * frames with a data interval of 1, but 11 (10.25) frames with a
+	 * data interval of 2.
+	 * (ep->freqmax << ep->datainterval overflows at 8.192 MHz for the
+	 * maximum datainterval value of 3, at USB full speed, higher for
+	 * USB high speed, noting that ep->freqmax is in units of
+	 * frames per packet in Q16.16 format.)
+	 */
+	maxsize = (((ep->freqmax << ep->datainterval) + 0xffff) >> 16) *
+			 (frame_bits >> 3);
+	if (tx_length_quirk)
+		maxsize += sizeof(__le32); /* Space for length descriptor */
+	/* but wMaxPacketSize might reduce this */
+	if (ep->maxpacksize && ep->maxpacksize < maxsize) {
+		/* whatever fits into a max. size packet */
+		unsigned int data_maxsize = maxsize = ep->maxpacksize;
+
+		if (tx_length_quirk)
+			/* Need to remove the length descriptor to calc freq */
+			data_maxsize -= sizeof(__le32);
+		ep->freqmax = (data_maxsize / (frame_bits >> 3))
+				<< (16 - ep->datainterval);
+	}
+
+	if (ep->fill_max)
+		ep->curpacksize = ep->maxpacksize;
+	else
+		ep->curpacksize = maxsize;
+
+	if (snd_usb_get_speed(chip->dev) != USB_SPEED_FULL) {
+		packs_per_ms = 8 >> ep->datainterval;
+		max_packs_per_urb = MAX_PACKS_HS;
+	} else {
+		packs_per_ms = 1;
+		max_packs_per_urb = MAX_PACKS;
+	}
+	if (ep->sync_source && !ep->implicit_fb_sync)
+		max_packs_per_urb = min(max_packs_per_urb,
+					1U << ep->sync_source->syncinterval);
+	max_packs_per_urb = max(1u, max_packs_per_urb >> ep->datainterval);
+
+	/*
+	 * Capture endpoints need to use small URBs because there's no way
+	 * to tell in advance where the next period will end, and we don't
+	 * want the next URB to complete much after the period ends.
+	 *
+	 * Playback endpoints with implicit sync much use the same parameters
+	 * as their corresponding capture endpoint.
+	 */
+	if (usb_pipein(ep->pipe) || ep->implicit_fb_sync) {
+
+		/* make capture URBs <= 1 ms and smaller than a period */
+		urb_packs = min(max_packs_per_urb, packs_per_ms);
+		while (urb_packs > 1 && urb_packs * maxsize >= ep->cur_period_bytes)
+			urb_packs >>= 1;
+		ep->nurbs = MAX_URBS;
+
+	/*
+	 * Playback endpoints without implicit sync are adjusted so that
+	 * a period fits as evenly as possible in the smallest number of
+	 * URBs.  The total number of URBs is adjusted to the size of the
+	 * ALSA buffer, subject to the MAX_URBS and MAX_QUEUE limits.
+	 */
+	} else {
+		/* determine how small a packet can be */
+		minsize = (ep->freqn >> (16 - ep->datainterval)) *
+				(frame_bits >> 3);
+		/* with sync from device, assume it can be 12% lower */
+		if (ep->sync_source)
+			minsize -= minsize >> 3;
+		minsize = max(minsize, 1u);
+
+		/* how many packets will contain an entire ALSA period? */
+		max_packs_per_period = DIV_ROUND_UP(ep->cur_period_bytes, minsize);
+
+		/* how many URBs will contain a period? */
+		urbs_per_period = DIV_ROUND_UP(max_packs_per_period,
+				max_packs_per_urb);
+		/* how many packets are needed in each URB? */
+		urb_packs = DIV_ROUND_UP(max_packs_per_period, urbs_per_period);
+
+		/* limit the number of frames in a single URB */
+		ep->max_urb_frames = DIV_ROUND_UP(ep->cur_period_frames,
+						  urbs_per_period);
+
+		/* try to use enough URBs to contain an entire ALSA buffer */
+		max_urbs = min((unsigned) MAX_URBS,
+				MAX_QUEUE * packs_per_ms / urb_packs);
+		ep->nurbs = min(max_urbs, urbs_per_period * ep->cur_buffer_periods);
+	}
+
+	/* allocate and initialize data urbs */
+	for (i = 0; i < ep->nurbs; i++) {
+		struct snd_urb_ctx *u = &ep->urb[i];
+		u->index = i;
+		u->ep = ep;
+		u->packets = urb_packs;
+		u->buffer_size = maxsize * u->packets;
+
+		if (fmt->fmt_type == UAC_FORMAT_TYPE_II)
+			u->packets++; /* for transfer delimiter */
+		u->urb = usb_alloc_urb(u->packets, GFP_KERNEL);
+		if (!u->urb)
+			goto out_of_memory;
+
+		u->urb->transfer_buffer =
+			usb_alloc_coherent(chip->dev, u->buffer_size,
+					   GFP_KERNEL, &u->urb->transfer_dma);
+		if (!u->urb->transfer_buffer)
+			goto out_of_memory;
+		u->urb->pipe = ep->pipe;
+		u->urb->transfer_flags = URB_NO_TRANSFER_DMA_MAP;
+		u->urb->interval = 1 << ep->datainterval;
+		u->urb->context = u;
+		u->urb->complete = snd_complete_urb;
+		INIT_LIST_HEAD(&u->ready_list);
+	}
+
+	return 0;
+
+out_of_memory:
+	release_urbs(ep, false);
+	return -ENOMEM;
+}
+
+/*
+ * configure a sync endpoint
+ */
+static int sync_ep_set_params(struct snd_usb_endpoint *ep)
+{
+	struct snd_usb_audio *chip = ep->chip;
+	int i;
+
+	usb_audio_dbg(chip, "Setting params for sync EP 0x%x, pipe 0x%x\n",
+		      ep->ep_num, ep->pipe);
+
+	ep->syncbuf = usb_alloc_coherent(chip->dev, SYNC_URBS * 4,
+					 GFP_KERNEL, &ep->sync_dma);
+	if (!ep->syncbuf)
+		return -ENOMEM;
+
+	ep->nurbs = SYNC_URBS;
+	for (i = 0; i < SYNC_URBS; i++) {
+		struct snd_urb_ctx *u = &ep->urb[i];
+		u->index = i;
+		u->ep = ep;
+		u->packets = 1;
+		u->urb = usb_alloc_urb(1, GFP_KERNEL);
+		if (!u->urb)
+			goto out_of_memory;
+		u->urb->transfer_buffer = ep->syncbuf + i * 4;
+		u->urb->transfer_dma = ep->sync_dma + i * 4;
+		u->urb->transfer_buffer_length = 4;
+		u->urb->pipe = ep->pipe;
+		u->urb->transfer_flags = URB_NO_TRANSFER_DMA_MAP;
+		u->urb->number_of_packets = 1;
+		u->urb->interval = 1 << ep->syncinterval;
+		u->urb->context = u;
+		u->urb->complete = snd_complete_urb;
+	}
+
+	return 0;
+
+out_of_memory:
+	release_urbs(ep, false);
+	return -ENOMEM;
+}
+
+/* update the rate of the referred clock; return the actual rate */
+static int update_clock_ref_rate(struct snd_usb_audio *chip,
+				 struct snd_usb_endpoint *ep)
+{
+	struct snd_usb_clock_ref *clock = ep->clock_ref;
+	int rate = ep->cur_rate;
+
+	if (!clock || clock->rate == rate)
+		return rate;
+	if (clock->rate) {
+		if (atomic_read(&clock->locked))
+			return clock->rate;
+		if (clock->rate != rate) {
+			usb_audio_err(chip, "Mismatched sample rate %d vs %d for EP 0x%x\n",
+				      clock->rate, rate, ep->ep_num);
+			return clock->rate;
+		}
+	}
+	clock->rate = rate;
+	clock->need_setup = true;
+	return rate;
+}
+
+/*
+ * snd_usb_endpoint_set_params: configure an snd_usb_endpoint
+ *
+ * It's called either from hw_params callback.
+ * Determine the number of URBs to be used on this endpoint.
+ * An endpoint must be configured before it can be started.
+ * An endpoint that is already running can not be reconfigured.
+ */
+int snd_usb_endpoint_set_params(struct snd_usb_audio *chip,
+				struct snd_usb_endpoint *ep)
+{
+	const struct audioformat *fmt = ep->cur_audiofmt;
+	int err = 0;
+
+	mutex_lock(&chip->mutex);
+	if (!ep->need_setup)
+		goto unlock;
+
+	/* release old buffers, if any */
+	err = release_urbs(ep, false);
+	if (err < 0)
+		goto unlock;
+
+	ep->datainterval = fmt->datainterval;
+	ep->maxpacksize = fmt->maxpacksize;
+	ep->fill_max = !!(fmt->attributes & UAC_EP_CS_ATTR_FILL_MAX);
+
+	if (snd_usb_get_speed(chip->dev) == USB_SPEED_FULL) {
+		ep->freqn = get_usb_full_speed_rate(ep->cur_rate);
+		ep->pps = 1000 >> ep->datainterval;
+	} else {
+		ep->freqn = get_usb_high_speed_rate(ep->cur_rate);
+		ep->pps = 8000 >> ep->datainterval;
+	}
+
+	ep->sample_rem = ep->cur_rate % ep->pps;
+	ep->packsize[0] = ep->cur_rate / ep->pps;
+	ep->packsize[1] = (ep->cur_rate + (ep->pps - 1)) / ep->pps;
+
+	/* calculate the frequency in 16.16 format */
+	ep->freqm = ep->freqn;
+	ep->freqshift = INT_MIN;
+
+	ep->phase = 0;
+
+	switch (ep->type) {
+	case  SND_USB_ENDPOINT_TYPE_DATA:
+		err = data_ep_set_params(ep);
+		break;
+	case  SND_USB_ENDPOINT_TYPE_SYNC:
+		err = sync_ep_set_params(ep);
+		break;
+	default:
+		err = -EINVAL;
+	}
+
+	usb_audio_dbg(chip, "Set up %d URBS, ret=%d\n", ep->nurbs, err);
+
+	if (err < 0)
+		goto unlock;
+
+	/* some unit conversions in runtime */
+	ep->maxframesize = ep->maxpacksize / ep->cur_frame_bytes;
+	ep->curframesize = ep->curpacksize / ep->cur_frame_bytes;
+
+	err = update_clock_ref_rate(chip, ep);
+	if (err >= 0) {
+		ep->need_setup = false;
+		err = 0;
+	}
+
+ unlock:
+	mutex_unlock(&chip->mutex);
+	return err;
+}
+
+static int init_sample_rate(struct snd_usb_audio *chip,
+			    struct snd_usb_endpoint *ep)
+{
+	struct snd_usb_clock_ref *clock = ep->clock_ref;
+	int rate, err;
+
+	rate = update_clock_ref_rate(chip, ep);
+	if (rate < 0)
+		return rate;
+	if (clock && !clock->need_setup)
+		return 0;
+
+	if (!ep->fixed_rate) {
+		err = snd_usb_init_sample_rate(chip, ep->cur_audiofmt, rate);
+		if (err < 0) {
+			if (clock)
+				clock->rate = 0; /* reset rate */
+			return err;
+		}
+	}
+
+	if (clock)
+		clock->need_setup = false;
+	return 0;
+}
+
+/*
+ * snd_usb_endpoint_prepare: Prepare the endpoint
+ *
+ * This function sets up the EP to be fully usable state.
+ * It's called either from prepare callback.
+ * The function checks need_setup flag, and performs nothing unless needed,
+ * so it's safe to call this multiple times.
+ *
+ * This returns zero if unchanged, 1 if the configuration has changed,
+ * or a negative error code.
+ */
+int snd_usb_endpoint_prepare(struct snd_usb_audio *chip,
+			     struct snd_usb_endpoint *ep)
+{
+	bool iface_first;
+	int err = 0;
+
+	mutex_lock(&chip->mutex);
+	if (WARN_ON(!ep->iface_ref))
+		goto unlock;
+	if (!ep->need_prepare)
+		goto unlock;
+
+	/* If the interface has been already set up, just set EP parameters */
+	if (!ep->iface_ref->need_setup) {
+		/* sample rate setup of UAC1 is per endpoint, and we need
+		 * to update at each EP configuration
+		 */
+		if (ep->cur_audiofmt->protocol == UAC_VERSION_1) {
+			err = init_sample_rate(chip, ep);
+			if (err < 0)
+				goto unlock;
+		}
+		goto done;
+	}
+
+	/* Need to deselect altsetting at first */
+	endpoint_set_interface(chip, ep, false);
+
+	/* Some UAC1 devices (e.g. Yamaha THR10) need the host interface
+	 * to be set up before parameter setups
+	 */
+	iface_first = ep->cur_audiofmt->protocol == UAC_VERSION_1;
+	/* Workaround for devices that require the interface setup at first like UAC1 */
+	if (chip->quirk_flags & QUIRK_FLAG_SET_IFACE_FIRST)
+		iface_first = true;
+	if (iface_first) {
+		err = endpoint_set_interface(chip, ep, true);
+		if (err < 0)
+			goto unlock;
+	}
+
+	err = snd_usb_init_pitch(chip, ep->cur_audiofmt);
+	if (err < 0)
+		goto unlock;
+
+	err = init_sample_rate(chip, ep);
+	if (err < 0)
+		goto unlock;
+
+	err = snd_usb_select_mode_quirk(chip, ep->cur_audiofmt);
+	if (err < 0)
+		goto unlock;
+
+	/* for UAC2/3, enable the interface altset here at last */
+	if (!iface_first) {
+		err = endpoint_set_interface(chip, ep, true);
+		if (err < 0)
+			goto unlock;
+	}
+
+	ep->iface_ref->need_setup = false;
+
+ done:
+	ep->need_prepare = false;
+	err = 1;
+
+unlock:
+	mutex_unlock(&chip->mutex);
+	return err;
+}
+
+/* get the current rate set to the given clock by any endpoint */
+int snd_usb_endpoint_get_clock_rate(struct snd_usb_audio *chip, int clock)
+{
+	struct snd_usb_clock_ref *ref;
+	int rate = 0;
+
+	if (!clock)
+		return 0;
+	mutex_lock(&chip->mutex);
+	list_for_each_entry(ref, &chip->clock_ref_list, list) {
+		if (ref->clock == clock) {
+			rate = ref->rate;
+			break;
+		}
+	}
+	mutex_unlock(&chip->mutex);
+	return rate;
+}
+
+/**
+ * snd_usb_endpoint_start: start an snd_usb_endpoint
+ *
+ * @ep: the endpoint to start
+ *
+ * A call to this function will increment the running count of the endpoint.
+ * In case it is not already running, the URBs for this endpoint will be
+ * submitted. Otherwise, this function does nothing.
+ *
+ * Must be balanced to calls of snd_usb_endpoint_stop().
+ *
+ * Returns an error if the URB submission failed, 0 in all other cases.
+ */
+int snd_usb_endpoint_start(struct snd_usb_endpoint *ep)
+{
+	bool is_playback = usb_pipeout(ep->pipe);
+	int err;
+	unsigned int i;
+
+	if (atomic_read(&ep->chip->shutdown))
+		return -EBADFD;
+
+	if (ep->sync_source)
+		WRITE_ONCE(ep->sync_source->sync_sink, ep);
+
+	usb_audio_dbg(ep->chip, "Starting %s EP 0x%x (running %d)\n",
+		      ep_type_name(ep->type), ep->ep_num,
+		      atomic_read(&ep->running));
+
+	/* already running? */
+	if (atomic_inc_return(&ep->running) != 1)
+		return 0;
+
+	if (ep->clock_ref)
+		atomic_inc(&ep->clock_ref->locked);
+
+	ep->active_mask = 0;
+	ep->unlink_mask = 0;
+	ep->phase = 0;
+	ep->sample_accum = 0;
+
+	snd_usb_endpoint_start_quirk(ep);
+
+	/*
+	 * If this endpoint has a data endpoint as implicit feedback source,
+	 * don't start the urbs here. Instead, mark them all as available,
+	 * wait for the record urbs to return and queue the playback urbs
+	 * from that context.
+	 */
+
+	if (!ep_state_update(ep, EP_STATE_STOPPED, EP_STATE_RUNNING))
+		goto __error;
+
+	if (snd_usb_endpoint_implicit_feedback_sink(ep) &&
+	    !(ep->chip->quirk_flags & QUIRK_FLAG_PLAYBACK_FIRST)) {
+		usb_audio_dbg(ep->chip, "No URB submission due to implicit fb sync\n");
+		i = 0;
+		goto fill_rest;
+	}
+
+	for (i = 0; i < ep->nurbs; i++) {
+		struct urb *urb = ep->urb[i].urb;
+
+		if (snd_BUG_ON(!urb))
+			goto __error;
+
+		if (is_playback)
+			err = prepare_outbound_urb(ep, urb->context, true);
+		else
+			err = prepare_inbound_urb(ep, urb->context);
+		if (err < 0) {
+			/* stop filling at applptr */
+			if (err == -EAGAIN)
+				break;
+			usb_audio_dbg(ep->chip,
+				      "EP 0x%x: failed to prepare urb: %d\n",
+				      ep->ep_num, err);
+			goto __error;
+		}
+
+		if (!atomic_read(&ep->chip->shutdown))
+			err = usb_submit_urb(urb, GFP_ATOMIC);
+		else
+			err = -ENODEV;
+		if (err < 0) {
+			if (!atomic_read(&ep->chip->shutdown))
+				usb_audio_err(ep->chip,
+					      "cannot submit urb %d, error %d: %s\n",
+					      i, err, usb_error_string(err));
+			goto __error;
+		}
+		set_bit(i, &ep->active_mask);
+		atomic_inc(&ep->submitted_urbs);
+	}
+
+	if (!i) {
+		usb_audio_dbg(ep->chip, "XRUN at starting EP 0x%x\n",
+			      ep->ep_num);
+		goto __error;
+	}
+
+	usb_audio_dbg(ep->chip, "%d URBs submitted for EP 0x%x\n",
+		      i, ep->ep_num);
+
+ fill_rest:
+	/* put the remaining URBs to ready list */
+	if (is_playback) {
+		for (; i < ep->nurbs; i++)
+			push_back_to_ready_list(ep, ep->urb + i);
+	}
+
+	return 0;
+
+__error:
+	snd_usb_endpoint_stop(ep, false);
+	return -EPIPE;
+}
+
+/**
+ * snd_usb_endpoint_stop: stop an snd_usb_endpoint
+ *
+ * @ep: the endpoint to stop (may be NULL)
+ * @keep_pending: keep in-flight URBs
+ *
+ * A call to this function will decrement the running count of the endpoint.
+ * In case the last user has requested the endpoint stop, the URBs will
+ * actually be deactivated.
+ *
+ * Must be balanced to calls of snd_usb_endpoint_start().
+ *
+ * The caller needs to synchronize the pending stop operation via
+ * snd_usb_endpoint_sync_pending_stop().
+ */
+void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep, bool keep_pending)
+{
+	if (!ep)
+		return;
+
+	usb_audio_dbg(ep->chip, "Stopping %s EP 0x%x (running %d)\n",
+		      ep_type_name(ep->type), ep->ep_num,
+		      atomic_read(&ep->running));
+
+	if (snd_BUG_ON(!atomic_read(&ep->running)))
+		return;
+
+	if (!atomic_dec_return(&ep->running)) {
+		if (ep->sync_source)
+			WRITE_ONCE(ep->sync_source->sync_sink, NULL);
+		stop_urbs(ep, false, keep_pending);
+		if (ep->clock_ref)
+			atomic_dec(&ep->clock_ref->locked);
+
+		if (ep->chip->quirk_flags & QUIRK_FLAG_FORCE_IFACE_RESET &&
+		    usb_pipeout(ep->pipe)) {
+			ep->need_prepare = true;
+			if (ep->iface_ref)
+				ep->iface_ref->need_setup = true;
+		}
+	}
+}
+
+/**
+ * snd_usb_endpoint_release: Tear down an snd_usb_endpoint
+ *
+ * @ep: the endpoint to release
+ *
+ * This function does not care for the endpoint's running count but will tear
+ * down all the streaming URBs immediately.
+ */
+void snd_usb_endpoint_release(struct snd_usb_endpoint *ep)
+{
+	release_urbs(ep, true);
+}
+
+/**
+ * snd_usb_endpoint_free_all: Free the resources of an snd_usb_endpoint
+ * @chip: The chip
+ *
+ * This free all endpoints and those resources
+ */
+void snd_usb_endpoint_free_all(struct snd_usb_audio *chip)
+{
+	struct snd_usb_endpoint *ep, *en;
+	struct snd_usb_iface_ref *ip, *in;
+	struct snd_usb_clock_ref *cp, *cn;
+
+	list_for_each_entry_safe(ep, en, &chip->ep_list, list)
+		kfree(ep);
+
+	list_for_each_entry_safe(ip, in, &chip->iface_ref_list, list)
+		kfree(ip);
+
+	list_for_each_entry_safe(cp, cn, &chip->clock_ref_list, list)
+		kfree(cp);
+}
+
+/*
+ * snd_usb_handle_sync_urb: parse an USB sync packet
+ *
+ * @ep: the endpoint to handle the packet
+ * @sender: the sending endpoint
+ * @urb: the received packet
+ *
+ * This function is called from the context of an endpoint that received
+ * the packet and is used to let another endpoint object handle the payload.
+ */
+static void snd_usb_handle_sync_urb(struct snd_usb_endpoint *ep,
+				    struct snd_usb_endpoint *sender,
+				    const struct urb *urb)
+{
+	int shift;
+	unsigned int f;
+	unsigned long flags;
+
+	snd_BUG_ON(ep == sender);
+
+	/*
+	 * In case the endpoint is operating in implicit feedback mode, prepare
+	 * a new outbound URB that has the same layout as the received packet
+	 * and add it to the list of pending urbs. queue_pending_output_urbs()
+	 * will take care of them later.
+	 */
+	if (snd_usb_endpoint_implicit_feedback_sink(ep) &&
+	    atomic_read(&ep->running)) {
+
+		/* implicit feedback case */
+		int i, bytes = 0;
+		struct snd_urb_ctx *in_ctx;
+		struct snd_usb_packet_info *out_packet;
+
+		in_ctx = urb->context;
+
+		/* Count overall packet size */
+		for (i = 0; i < in_ctx->packets; i++)
+			if (urb->iso_frame_desc[i].status == 0)
+				bytes += urb->iso_frame_desc[i].actual_length;
+
+		/*
+		 * skip empty packets. At least M-Audio's Fast Track Ultra stops
+		 * streaming once it received a 0-byte OUT URB
+		 */
+		if (bytes == 0)
+			return;
+
+		spin_lock_irqsave(&ep->lock, flags);
+		if (ep->next_packet_queued >= ARRAY_SIZE(ep->next_packet)) {
+			spin_unlock_irqrestore(&ep->lock, flags);
+			usb_audio_err(ep->chip,
+				      "next package FIFO overflow EP 0x%x\n",
+				      ep->ep_num);
+			notify_xrun(ep);
+			return;
+		}
+
+		out_packet = next_packet_fifo_enqueue(ep);
+
+		/*
+		 * Iterate through the inbound packet and prepare the lengths
+		 * for the output packet. The OUT packet we are about to send
+		 * will have the same amount of payload bytes per stride as the
+		 * IN packet we just received. Since the actual size is scaled
+		 * by the stride, use the sender stride to calculate the length
+		 * in case the number of channels differ between the implicitly
+		 * fed-back endpoint and the synchronizing endpoint.
+		 */
+
+		out_packet->packets = in_ctx->packets;
+		for (i = 0; i < in_ctx->packets; i++) {
+			if (urb->iso_frame_desc[i].status == 0)
+				out_packet->packet_size[i] =
+					urb->iso_frame_desc[i].actual_length / sender->stride;
+			else
+				out_packet->packet_size[i] = 0;
+		}
+
+		spin_unlock_irqrestore(&ep->lock, flags);
+		snd_usb_queue_pending_output_urbs(ep, false);
+
+		return;
+	}
+
+	/*
+	 * process after playback sync complete
+	 *
+	 * Full speed devices report feedback values in 10.14 format as samples
+	 * per frame, high speed devices in 16.16 format as samples per
+	 * microframe.
+	 *
+	 * Because the Audio Class 1 spec was written before USB 2.0, many high
+	 * speed devices use a wrong interpretation, some others use an
+	 * entirely different format.
+	 *
+	 * Therefore, we cannot predict what format any particular device uses
+	 * and must detect it automatically.
+	 */
+
+	if (urb->iso_frame_desc[0].status != 0 ||
+	    urb->iso_frame_desc[0].actual_length < 3)
+		return;
+
+	f = le32_to_cpup(urb->transfer_buffer);
+	if (urb->iso_frame_desc[0].actual_length == 3)
+		f &= 0x00ffffff;
+	else
+		f &= 0x0fffffff;
+
+	if (f == 0)
+		return;
+
+	if (unlikely(sender->tenor_fb_quirk)) {
+		/*
+		 * Devices based on Tenor 8802 chipsets (TEAC UD-H01
+		 * and others) sometimes change the feedback value
+		 * by +/- 0x1.0000.
+		 */
+		if (f < ep->freqn - 0x8000)
+			f += 0xf000;
+		else if (f > ep->freqn + 0x8000)
+			f -= 0xf000;
+	} else if (unlikely(ep->freqshift == INT_MIN)) {
+		/*
+		 * The first time we see a feedback value, determine its format
+		 * by shifting it left or right until it matches the nominal
+		 * frequency value.  This assumes that the feedback does not
+		 * differ from the nominal value more than +50% or -25%.
+		 */
+		shift = 0;
+		while (f < ep->freqn - ep->freqn / 4) {
+			f <<= 1;
+			shift++;
+		}
+		while (f > ep->freqn + ep->freqn / 2) {
+			f >>= 1;
+			shift--;
+		}
+		ep->freqshift = shift;
+	} else if (ep->freqshift >= 0)
+		f <<= ep->freqshift;
+	else
+		f >>= -ep->freqshift;
+
+	if (likely(f >= ep->freqn - ep->freqn / 8 && f <= ep->freqmax)) {
+		/*
+		 * If the frequency looks valid, set it.
+		 * This value is referred to in prepare_playback_urb().
+		 */
+		spin_lock_irqsave(&ep->lock, flags);
+		ep->freqm = f;
+		spin_unlock_irqrestore(&ep->lock, flags);
+	} else {
+		/*
+		 * Out of range; maybe the shift value is wrong.
+		 * Reset it so that we autodetect again the next time.
+		 */
+		ep->freqshift = INT_MIN;
+	}
+}
+