xref: /linux/sound/usb/endpoint.c (revision d198b34f3855eee2571dda03eea75a09c7c31480)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  */
4 
5 #include <linux/gfp.h>
6 #include <linux/init.h>
7 #include <linux/ratelimit.h>
8 #include <linux/usb.h>
9 #include <linux/usb/audio.h>
10 #include <linux/slab.h>
11 
12 #include <sound/core.h>
13 #include <sound/pcm.h>
14 #include <sound/pcm_params.h>
15 
16 #include "usbaudio.h"
17 #include "helper.h"
18 #include "card.h"
19 #include "endpoint.h"
20 #include "pcm.h"
21 #include "quirks.h"
22 
23 #define EP_FLAG_RUNNING		1
24 #define EP_FLAG_STOPPING	2
25 
26 /*
27  * snd_usb_endpoint is a model that abstracts everything related to an
28  * USB endpoint and its streaming.
29  *
30  * There are functions to activate and deactivate the streaming URBs and
31  * optional callbacks to let the pcm logic handle the actual content of the
32  * packets for playback and record. Thus, the bus streaming and the audio
33  * handlers are fully decoupled.
34  *
35  * There are two different types of endpoints in audio applications.
36  *
37  * SND_USB_ENDPOINT_TYPE_DATA handles full audio data payload for both
38  * inbound and outbound traffic.
39  *
40  * SND_USB_ENDPOINT_TYPE_SYNC endpoints are for inbound traffic only and
41  * expect the payload to carry Q10.14 / Q16.16 formatted sync information
42  * (3 or 4 bytes).
43  *
44  * Each endpoint has to be configured prior to being used by calling
45  * snd_usb_endpoint_set_params().
46  *
47  * The model incorporates a reference counting, so that multiple users
48  * can call snd_usb_endpoint_start() and snd_usb_endpoint_stop(), and
49  * only the first user will effectively start the URBs, and only the last
50  * one to stop it will tear the URBs down again.
51  */
52 
53 /*
54  * convert a sampling rate into our full speed format (fs/1000 in Q16.16)
55  * this will overflow at approx 524 kHz
56  */
57 static inline unsigned get_usb_full_speed_rate(unsigned int rate)
58 {
59 	return ((rate << 13) + 62) / 125;
60 }
61 
62 /*
63  * convert a sampling rate into USB high speed format (fs/8000 in Q16.16)
64  * this will overflow at approx 4 MHz
65  */
66 static inline unsigned get_usb_high_speed_rate(unsigned int rate)
67 {
68 	return ((rate << 10) + 62) / 125;
69 }
70 
71 /*
72  * release a urb data
73  */
74 static void release_urb_ctx(struct snd_urb_ctx *u)
75 {
76 	if (u->buffer_size)
77 		usb_free_coherent(u->ep->chip->dev, u->buffer_size,
78 				  u->urb->transfer_buffer,
79 				  u->urb->transfer_dma);
80 	usb_free_urb(u->urb);
81 	u->urb = NULL;
82 }
83 
84 static const char *usb_error_string(int err)
85 {
86 	switch (err) {
87 	case -ENODEV:
88 		return "no device";
89 	case -ENOENT:
90 		return "endpoint not enabled";
91 	case -EPIPE:
92 		return "endpoint stalled";
93 	case -ENOSPC:
94 		return "not enough bandwidth";
95 	case -ESHUTDOWN:
96 		return "device disabled";
97 	case -EHOSTUNREACH:
98 		return "device suspended";
99 	case -EINVAL:
100 	case -EAGAIN:
101 	case -EFBIG:
102 	case -EMSGSIZE:
103 		return "internal error";
104 	default:
105 		return "unknown error";
106 	}
107 }
108 
109 /**
110  * snd_usb_endpoint_implicit_feedback_sink: Report endpoint usage type
111  *
112  * @ep: The snd_usb_endpoint
113  *
114  * Determine whether an endpoint is driven by an implicit feedback
115  * data endpoint source.
116  */
117 int snd_usb_endpoint_implicit_feedback_sink(struct snd_usb_endpoint *ep)
118 {
119 	return  ep->sync_master &&
120 		ep->sync_master->type == SND_USB_ENDPOINT_TYPE_DATA &&
121 		ep->type == SND_USB_ENDPOINT_TYPE_DATA &&
122 		usb_pipeout(ep->pipe);
123 }
124 
125 /*
126  * For streaming based on information derived from sync endpoints,
127  * prepare_outbound_urb_sizes() will call next_packet_size() to
128  * determine the number of samples to be sent in the next packet.
129  *
130  * For implicit feedback, next_packet_size() is unused.
131  */
132 int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep)
133 {
134 	unsigned long flags;
135 	int ret;
136 
137 	if (ep->fill_max)
138 		return ep->maxframesize;
139 
140 	spin_lock_irqsave(&ep->lock, flags);
141 	ep->phase = (ep->phase & 0xffff)
142 		+ (ep->freqm << ep->datainterval);
143 	ret = min(ep->phase >> 16, ep->maxframesize);
144 	spin_unlock_irqrestore(&ep->lock, flags);
145 
146 	return ret;
147 }
148 
149 static void retire_outbound_urb(struct snd_usb_endpoint *ep,
150 				struct snd_urb_ctx *urb_ctx)
151 {
152 	if (ep->retire_data_urb)
153 		ep->retire_data_urb(ep->data_subs, urb_ctx->urb);
154 }
155 
156 static void retire_inbound_urb(struct snd_usb_endpoint *ep,
157 			       struct snd_urb_ctx *urb_ctx)
158 {
159 	struct urb *urb = urb_ctx->urb;
160 
161 	if (unlikely(ep->skip_packets > 0)) {
162 		ep->skip_packets--;
163 		return;
164 	}
165 
166 	if (ep->sync_slave)
167 		snd_usb_handle_sync_urb(ep->sync_slave, ep, urb);
168 
169 	if (ep->retire_data_urb)
170 		ep->retire_data_urb(ep->data_subs, urb);
171 }
172 
173 static void prepare_silent_urb(struct snd_usb_endpoint *ep,
174 			       struct snd_urb_ctx *ctx)
175 {
176 	struct urb *urb = ctx->urb;
177 	unsigned int offs = 0;
178 	unsigned int extra = 0;
179 	__le32 packet_length;
180 	int i;
181 
182 	/* For tx_length_quirk, put packet length at start of packet */
183 	if (ep->chip->tx_length_quirk)
184 		extra = sizeof(packet_length);
185 
186 	for (i = 0; i < ctx->packets; ++i) {
187 		unsigned int offset;
188 		unsigned int length;
189 		int counts;
190 
191 		if (ctx->packet_size[i])
192 			counts = ctx->packet_size[i];
193 		else
194 			counts = snd_usb_endpoint_next_packet_size(ep);
195 
196 		length = counts * ep->stride; /* number of silent bytes */
197 		offset = offs * ep->stride + extra * i;
198 		urb->iso_frame_desc[i].offset = offset;
199 		urb->iso_frame_desc[i].length = length + extra;
200 		if (extra) {
201 			packet_length = cpu_to_le32(length);
202 			memcpy(urb->transfer_buffer + offset,
203 			       &packet_length, sizeof(packet_length));
204 		}
205 		memset(urb->transfer_buffer + offset + extra,
206 		       ep->silence_value, length);
207 		offs += counts;
208 	}
209 
210 	urb->number_of_packets = ctx->packets;
211 	urb->transfer_buffer_length = offs * ep->stride + ctx->packets * extra;
212 }
213 
214 /*
215  * Prepare a PLAYBACK urb for submission to the bus.
216  */
217 static void prepare_outbound_urb(struct snd_usb_endpoint *ep,
218 				 struct snd_urb_ctx *ctx)
219 {
220 	struct urb *urb = ctx->urb;
221 	unsigned char *cp = urb->transfer_buffer;
222 
223 	urb->dev = ep->chip->dev; /* we need to set this at each time */
224 
225 	switch (ep->type) {
226 	case SND_USB_ENDPOINT_TYPE_DATA:
227 		if (ep->prepare_data_urb) {
228 			ep->prepare_data_urb(ep->data_subs, urb);
229 		} else {
230 			/* no data provider, so send silence */
231 			prepare_silent_urb(ep, ctx);
232 		}
233 		break;
234 
235 	case SND_USB_ENDPOINT_TYPE_SYNC:
236 		if (snd_usb_get_speed(ep->chip->dev) >= USB_SPEED_HIGH) {
237 			/*
238 			 * fill the length and offset of each urb descriptor.
239 			 * the fixed 12.13 frequency is passed as 16.16 through the pipe.
240 			 */
241 			urb->iso_frame_desc[0].length = 4;
242 			urb->iso_frame_desc[0].offset = 0;
243 			cp[0] = ep->freqn;
244 			cp[1] = ep->freqn >> 8;
245 			cp[2] = ep->freqn >> 16;
246 			cp[3] = ep->freqn >> 24;
247 		} else {
248 			/*
249 			 * fill the length and offset of each urb descriptor.
250 			 * the fixed 10.14 frequency is passed through the pipe.
251 			 */
252 			urb->iso_frame_desc[0].length = 3;
253 			urb->iso_frame_desc[0].offset = 0;
254 			cp[0] = ep->freqn >> 2;
255 			cp[1] = ep->freqn >> 10;
256 			cp[2] = ep->freqn >> 18;
257 		}
258 
259 		break;
260 	}
261 }
262 
263 /*
264  * Prepare a CAPTURE or SYNC urb for submission to the bus.
265  */
266 static inline void prepare_inbound_urb(struct snd_usb_endpoint *ep,
267 				       struct snd_urb_ctx *urb_ctx)
268 {
269 	int i, offs;
270 	struct urb *urb = urb_ctx->urb;
271 
272 	urb->dev = ep->chip->dev; /* we need to set this at each time */
273 
274 	switch (ep->type) {
275 	case SND_USB_ENDPOINT_TYPE_DATA:
276 		offs = 0;
277 		for (i = 0; i < urb_ctx->packets; i++) {
278 			urb->iso_frame_desc[i].offset = offs;
279 			urb->iso_frame_desc[i].length = ep->curpacksize;
280 			offs += ep->curpacksize;
281 		}
282 
283 		urb->transfer_buffer_length = offs;
284 		urb->number_of_packets = urb_ctx->packets;
285 		break;
286 
287 	case SND_USB_ENDPOINT_TYPE_SYNC:
288 		urb->iso_frame_desc[0].length = min(4u, ep->syncmaxsize);
289 		urb->iso_frame_desc[0].offset = 0;
290 		break;
291 	}
292 }
293 
294 /*
295  * Send output urbs that have been prepared previously. URBs are dequeued
296  * from ep->ready_playback_urbs and in case there there aren't any available
297  * or there are no packets that have been prepared, this function does
298  * nothing.
299  *
300  * The reason why the functionality of sending and preparing URBs is separated
301  * is that host controllers don't guarantee the order in which they return
302  * inbound and outbound packets to their submitters.
303  *
304  * This function is only used for implicit feedback endpoints. For endpoints
305  * driven by dedicated sync endpoints, URBs are immediately re-submitted
306  * from their completion handler.
307  */
308 static void queue_pending_output_urbs(struct snd_usb_endpoint *ep)
309 {
310 	while (test_bit(EP_FLAG_RUNNING, &ep->flags)) {
311 
312 		unsigned long flags;
313 		struct snd_usb_packet_info *uninitialized_var(packet);
314 		struct snd_urb_ctx *ctx = NULL;
315 		int err, i;
316 
317 		spin_lock_irqsave(&ep->lock, flags);
318 		if (ep->next_packet_read_pos != ep->next_packet_write_pos) {
319 			packet = ep->next_packet + ep->next_packet_read_pos;
320 			ep->next_packet_read_pos++;
321 			ep->next_packet_read_pos %= MAX_URBS;
322 
323 			/* take URB out of FIFO */
324 			if (!list_empty(&ep->ready_playback_urbs))
325 				ctx = list_first_entry(&ep->ready_playback_urbs,
326 					       struct snd_urb_ctx, ready_list);
327 		}
328 		spin_unlock_irqrestore(&ep->lock, flags);
329 
330 		if (ctx == NULL)
331 			return;
332 
333 		list_del_init(&ctx->ready_list);
334 
335 		/* copy over the length information */
336 		for (i = 0; i < packet->packets; i++)
337 			ctx->packet_size[i] = packet->packet_size[i];
338 
339 		/* call the data handler to fill in playback data */
340 		prepare_outbound_urb(ep, ctx);
341 
342 		err = usb_submit_urb(ctx->urb, GFP_ATOMIC);
343 		if (err < 0)
344 			usb_audio_err(ep->chip,
345 				"Unable to submit urb #%d: %d (urb %p)\n",
346 				ctx->index, err, ctx->urb);
347 		else
348 			set_bit(ctx->index, &ep->active_mask);
349 	}
350 }
351 
352 /*
353  * complete callback for urbs
354  */
355 static void snd_complete_urb(struct urb *urb)
356 {
357 	struct snd_urb_ctx *ctx = urb->context;
358 	struct snd_usb_endpoint *ep = ctx->ep;
359 	struct snd_pcm_substream *substream;
360 	unsigned long flags;
361 	int err;
362 
363 	if (unlikely(urb->status == -ENOENT ||		/* unlinked */
364 		     urb->status == -ENODEV ||		/* device removed */
365 		     urb->status == -ECONNRESET ||	/* unlinked */
366 		     urb->status == -ESHUTDOWN))	/* device disabled */
367 		goto exit_clear;
368 	/* device disconnected */
369 	if (unlikely(atomic_read(&ep->chip->shutdown)))
370 		goto exit_clear;
371 
372 	if (unlikely(!test_bit(EP_FLAG_RUNNING, &ep->flags)))
373 		goto exit_clear;
374 
375 	if (usb_pipeout(ep->pipe)) {
376 		retire_outbound_urb(ep, ctx);
377 		/* can be stopped during retire callback */
378 		if (unlikely(!test_bit(EP_FLAG_RUNNING, &ep->flags)))
379 			goto exit_clear;
380 
381 		if (snd_usb_endpoint_implicit_feedback_sink(ep)) {
382 			spin_lock_irqsave(&ep->lock, flags);
383 			list_add_tail(&ctx->ready_list, &ep->ready_playback_urbs);
384 			spin_unlock_irqrestore(&ep->lock, flags);
385 			queue_pending_output_urbs(ep);
386 
387 			goto exit_clear;
388 		}
389 
390 		prepare_outbound_urb(ep, ctx);
391 		/* can be stopped during prepare callback */
392 		if (unlikely(!test_bit(EP_FLAG_RUNNING, &ep->flags)))
393 			goto exit_clear;
394 	} else {
395 		retire_inbound_urb(ep, ctx);
396 		/* can be stopped during retire callback */
397 		if (unlikely(!test_bit(EP_FLAG_RUNNING, &ep->flags)))
398 			goto exit_clear;
399 
400 		prepare_inbound_urb(ep, ctx);
401 	}
402 
403 	err = usb_submit_urb(urb, GFP_ATOMIC);
404 	if (err == 0)
405 		return;
406 
407 	usb_audio_err(ep->chip, "cannot submit urb (err = %d)\n", err);
408 	if (ep->data_subs && ep->data_subs->pcm_substream) {
409 		substream = ep->data_subs->pcm_substream;
410 		snd_pcm_stop_xrun(substream);
411 	}
412 
413 exit_clear:
414 	clear_bit(ctx->index, &ep->active_mask);
415 }
416 
417 /**
418  * snd_usb_add_endpoint: Add an endpoint to an USB audio chip
419  *
420  * @chip: The chip
421  * @alts: The USB host interface
422  * @ep_num: The number of the endpoint to use
423  * @direction: SNDRV_PCM_STREAM_PLAYBACK or SNDRV_PCM_STREAM_CAPTURE
424  * @type: SND_USB_ENDPOINT_TYPE_DATA or SND_USB_ENDPOINT_TYPE_SYNC
425  *
426  * If the requested endpoint has not been added to the given chip before,
427  * a new instance is created. Otherwise, a pointer to the previoulsy
428  * created instance is returned. In case of any error, NULL is returned.
429  *
430  * New endpoints will be added to chip->ep_list and must be freed by
431  * calling snd_usb_endpoint_free().
432  *
433  * For SND_USB_ENDPOINT_TYPE_SYNC, the caller needs to guarantee that
434  * bNumEndpoints > 1 beforehand.
435  */
436 struct snd_usb_endpoint *snd_usb_add_endpoint(struct snd_usb_audio *chip,
437 					      struct usb_host_interface *alts,
438 					      int ep_num, int direction, int type)
439 {
440 	struct snd_usb_endpoint *ep;
441 	int is_playback = direction == SNDRV_PCM_STREAM_PLAYBACK;
442 
443 	if (WARN_ON(!alts))
444 		return NULL;
445 
446 	mutex_lock(&chip->mutex);
447 
448 	list_for_each_entry(ep, &chip->ep_list, list) {
449 		if (ep->ep_num == ep_num &&
450 		    ep->iface == alts->desc.bInterfaceNumber &&
451 		    ep->altsetting == alts->desc.bAlternateSetting) {
452 			usb_audio_dbg(ep->chip,
453 				      "Re-using EP %x in iface %d,%d @%p\n",
454 					ep_num, ep->iface, ep->altsetting, ep);
455 			goto __exit_unlock;
456 		}
457 	}
458 
459 	usb_audio_dbg(chip, "Creating new %s %s endpoint #%x\n",
460 		    is_playback ? "playback" : "capture",
461 		    type == SND_USB_ENDPOINT_TYPE_DATA ? "data" : "sync",
462 		    ep_num);
463 
464 	ep = kzalloc(sizeof(*ep), GFP_KERNEL);
465 	if (!ep)
466 		goto __exit_unlock;
467 
468 	ep->chip = chip;
469 	spin_lock_init(&ep->lock);
470 	ep->type = type;
471 	ep->ep_num = ep_num;
472 	ep->iface = alts->desc.bInterfaceNumber;
473 	ep->altsetting = alts->desc.bAlternateSetting;
474 	INIT_LIST_HEAD(&ep->ready_playback_urbs);
475 	ep_num &= USB_ENDPOINT_NUMBER_MASK;
476 
477 	if (is_playback)
478 		ep->pipe = usb_sndisocpipe(chip->dev, ep_num);
479 	else
480 		ep->pipe = usb_rcvisocpipe(chip->dev, ep_num);
481 
482 	if (type == SND_USB_ENDPOINT_TYPE_SYNC) {
483 		if (get_endpoint(alts, 1)->bLength >= USB_DT_ENDPOINT_AUDIO_SIZE &&
484 		    get_endpoint(alts, 1)->bRefresh >= 1 &&
485 		    get_endpoint(alts, 1)->bRefresh <= 9)
486 			ep->syncinterval = get_endpoint(alts, 1)->bRefresh;
487 		else if (snd_usb_get_speed(chip->dev) == USB_SPEED_FULL)
488 			ep->syncinterval = 1;
489 		else if (get_endpoint(alts, 1)->bInterval >= 1 &&
490 			 get_endpoint(alts, 1)->bInterval <= 16)
491 			ep->syncinterval = get_endpoint(alts, 1)->bInterval - 1;
492 		else
493 			ep->syncinterval = 3;
494 
495 		ep->syncmaxsize = le16_to_cpu(get_endpoint(alts, 1)->wMaxPacketSize);
496 	}
497 
498 	list_add_tail(&ep->list, &chip->ep_list);
499 
500 __exit_unlock:
501 	mutex_unlock(&chip->mutex);
502 
503 	return ep;
504 }
505 
506 /*
507  *  wait until all urbs are processed.
508  */
509 static int wait_clear_urbs(struct snd_usb_endpoint *ep)
510 {
511 	unsigned long end_time = jiffies + msecs_to_jiffies(1000);
512 	int alive;
513 
514 	do {
515 		alive = bitmap_weight(&ep->active_mask, ep->nurbs);
516 		if (!alive)
517 			break;
518 
519 		schedule_timeout_uninterruptible(1);
520 	} while (time_before(jiffies, end_time));
521 
522 	if (alive)
523 		usb_audio_err(ep->chip,
524 			"timeout: still %d active urbs on EP #%x\n",
525 			alive, ep->ep_num);
526 	clear_bit(EP_FLAG_STOPPING, &ep->flags);
527 
528 	ep->data_subs = NULL;
529 	ep->sync_slave = NULL;
530 	ep->retire_data_urb = NULL;
531 	ep->prepare_data_urb = NULL;
532 
533 	return 0;
534 }
535 
536 /* sync the pending stop operation;
537  * this function itself doesn't trigger the stop operation
538  */
539 void snd_usb_endpoint_sync_pending_stop(struct snd_usb_endpoint *ep)
540 {
541 	if (ep && test_bit(EP_FLAG_STOPPING, &ep->flags))
542 		wait_clear_urbs(ep);
543 }
544 
545 /*
546  * unlink active urbs.
547  */
548 static int deactivate_urbs(struct snd_usb_endpoint *ep, bool force)
549 {
550 	unsigned int i;
551 
552 	if (!force && atomic_read(&ep->chip->shutdown)) /* to be sure... */
553 		return -EBADFD;
554 
555 	clear_bit(EP_FLAG_RUNNING, &ep->flags);
556 
557 	INIT_LIST_HEAD(&ep->ready_playback_urbs);
558 	ep->next_packet_read_pos = 0;
559 	ep->next_packet_write_pos = 0;
560 
561 	for (i = 0; i < ep->nurbs; i++) {
562 		if (test_bit(i, &ep->active_mask)) {
563 			if (!test_and_set_bit(i, &ep->unlink_mask)) {
564 				struct urb *u = ep->urb[i].urb;
565 				usb_unlink_urb(u);
566 			}
567 		}
568 	}
569 
570 	return 0;
571 }
572 
573 /*
574  * release an endpoint's urbs
575  */
576 static void release_urbs(struct snd_usb_endpoint *ep, int force)
577 {
578 	int i;
579 
580 	/* route incoming urbs to nirvana */
581 	ep->retire_data_urb = NULL;
582 	ep->prepare_data_urb = NULL;
583 
584 	/* stop urbs */
585 	deactivate_urbs(ep, force);
586 	wait_clear_urbs(ep);
587 
588 	for (i = 0; i < ep->nurbs; i++)
589 		release_urb_ctx(&ep->urb[i]);
590 
591 	if (ep->syncbuf)
592 		usb_free_coherent(ep->chip->dev, SYNC_URBS * 4,
593 				  ep->syncbuf, ep->sync_dma);
594 
595 	ep->syncbuf = NULL;
596 	ep->nurbs = 0;
597 }
598 
599 /*
600  * configure a data endpoint
601  */
602 static int data_ep_set_params(struct snd_usb_endpoint *ep,
603 			      snd_pcm_format_t pcm_format,
604 			      unsigned int channels,
605 			      unsigned int period_bytes,
606 			      unsigned int frames_per_period,
607 			      unsigned int periods_per_buffer,
608 			      struct audioformat *fmt,
609 			      struct snd_usb_endpoint *sync_ep)
610 {
611 	unsigned int maxsize, minsize, packs_per_ms, max_packs_per_urb;
612 	unsigned int max_packs_per_period, urbs_per_period, urb_packs;
613 	unsigned int max_urbs, i;
614 	int frame_bits = snd_pcm_format_physical_width(pcm_format) * channels;
615 	int tx_length_quirk = (ep->chip->tx_length_quirk &&
616 			       usb_pipeout(ep->pipe));
617 
618 	if (pcm_format == SNDRV_PCM_FORMAT_DSD_U16_LE && fmt->dsd_dop) {
619 		/*
620 		 * When operating in DSD DOP mode, the size of a sample frame
621 		 * in hardware differs from the actual physical format width
622 		 * because we need to make room for the DOP markers.
623 		 */
624 		frame_bits += channels << 3;
625 	}
626 
627 	ep->datainterval = fmt->datainterval;
628 	ep->stride = frame_bits >> 3;
629 
630 	switch (pcm_format) {
631 	case SNDRV_PCM_FORMAT_U8:
632 		ep->silence_value = 0x80;
633 		break;
634 	case SNDRV_PCM_FORMAT_DSD_U8:
635 	case SNDRV_PCM_FORMAT_DSD_U16_LE:
636 	case SNDRV_PCM_FORMAT_DSD_U32_LE:
637 	case SNDRV_PCM_FORMAT_DSD_U16_BE:
638 	case SNDRV_PCM_FORMAT_DSD_U32_BE:
639 		ep->silence_value = 0x69;
640 		break;
641 	default:
642 		ep->silence_value = 0;
643 	}
644 
645 	/* assume max. frequency is 50% higher than nominal */
646 	ep->freqmax = ep->freqn + (ep->freqn >> 1);
647 	/* Round up freqmax to nearest integer in order to calculate maximum
648 	 * packet size, which must represent a whole number of frames.
649 	 * This is accomplished by adding 0x0.ffff before converting the
650 	 * Q16.16 format into integer.
651 	 * In order to accurately calculate the maximum packet size when
652 	 * the data interval is more than 1 (i.e. ep->datainterval > 0),
653 	 * multiply by the data interval prior to rounding. For instance,
654 	 * a freqmax of 41 kHz will result in a max packet size of 6 (5.125)
655 	 * frames with a data interval of 1, but 11 (10.25) frames with a
656 	 * data interval of 2.
657 	 * (ep->freqmax << ep->datainterval overflows at 8.192 MHz for the
658 	 * maximum datainterval value of 3, at USB full speed, higher for
659 	 * USB high speed, noting that ep->freqmax is in units of
660 	 * frames per packet in Q16.16 format.)
661 	 */
662 	maxsize = (((ep->freqmax << ep->datainterval) + 0xffff) >> 16) *
663 			 (frame_bits >> 3);
664 	if (tx_length_quirk)
665 		maxsize += sizeof(__le32); /* Space for length descriptor */
666 	/* but wMaxPacketSize might reduce this */
667 	if (ep->maxpacksize && ep->maxpacksize < maxsize) {
668 		/* whatever fits into a max. size packet */
669 		unsigned int data_maxsize = maxsize = ep->maxpacksize;
670 
671 		if (tx_length_quirk)
672 			/* Need to remove the length descriptor to calc freq */
673 			data_maxsize -= sizeof(__le32);
674 		ep->freqmax = (data_maxsize / (frame_bits >> 3))
675 				<< (16 - ep->datainterval);
676 	}
677 
678 	if (ep->fill_max)
679 		ep->curpacksize = ep->maxpacksize;
680 	else
681 		ep->curpacksize = maxsize;
682 
683 	if (snd_usb_get_speed(ep->chip->dev) != USB_SPEED_FULL) {
684 		packs_per_ms = 8 >> ep->datainterval;
685 		max_packs_per_urb = MAX_PACKS_HS;
686 	} else {
687 		packs_per_ms = 1;
688 		max_packs_per_urb = MAX_PACKS;
689 	}
690 	if (sync_ep && !snd_usb_endpoint_implicit_feedback_sink(ep))
691 		max_packs_per_urb = min(max_packs_per_urb,
692 					1U << sync_ep->syncinterval);
693 	max_packs_per_urb = max(1u, max_packs_per_urb >> ep->datainterval);
694 
695 	/*
696 	 * Capture endpoints need to use small URBs because there's no way
697 	 * to tell in advance where the next period will end, and we don't
698 	 * want the next URB to complete much after the period ends.
699 	 *
700 	 * Playback endpoints with implicit sync much use the same parameters
701 	 * as their corresponding capture endpoint.
702 	 */
703 	if (usb_pipein(ep->pipe) ||
704 			snd_usb_endpoint_implicit_feedback_sink(ep)) {
705 
706 		urb_packs = packs_per_ms;
707 		/*
708 		 * Wireless devices can poll at a max rate of once per 4ms.
709 		 * For dataintervals less than 5, increase the packet count to
710 		 * allow the host controller to use bursting to fill in the
711 		 * gaps.
712 		 */
713 		if (snd_usb_get_speed(ep->chip->dev) == USB_SPEED_WIRELESS) {
714 			int interval = ep->datainterval;
715 			while (interval < 5) {
716 				urb_packs <<= 1;
717 				++interval;
718 			}
719 		}
720 		/* make capture URBs <= 1 ms and smaller than a period */
721 		urb_packs = min(max_packs_per_urb, urb_packs);
722 		while (urb_packs > 1 && urb_packs * maxsize >= period_bytes)
723 			urb_packs >>= 1;
724 		ep->nurbs = MAX_URBS;
725 
726 	/*
727 	 * Playback endpoints without implicit sync are adjusted so that
728 	 * a period fits as evenly as possible in the smallest number of
729 	 * URBs.  The total number of URBs is adjusted to the size of the
730 	 * ALSA buffer, subject to the MAX_URBS and MAX_QUEUE limits.
731 	 */
732 	} else {
733 		/* determine how small a packet can be */
734 		minsize = (ep->freqn >> (16 - ep->datainterval)) *
735 				(frame_bits >> 3);
736 		/* with sync from device, assume it can be 12% lower */
737 		if (sync_ep)
738 			minsize -= minsize >> 3;
739 		minsize = max(minsize, 1u);
740 
741 		/* how many packets will contain an entire ALSA period? */
742 		max_packs_per_period = DIV_ROUND_UP(period_bytes, minsize);
743 
744 		/* how many URBs will contain a period? */
745 		urbs_per_period = DIV_ROUND_UP(max_packs_per_period,
746 				max_packs_per_urb);
747 		/* how many packets are needed in each URB? */
748 		urb_packs = DIV_ROUND_UP(max_packs_per_period, urbs_per_period);
749 
750 		/* limit the number of frames in a single URB */
751 		ep->max_urb_frames = DIV_ROUND_UP(frames_per_period,
752 					urbs_per_period);
753 
754 		/* try to use enough URBs to contain an entire ALSA buffer */
755 		max_urbs = min((unsigned) MAX_URBS,
756 				MAX_QUEUE * packs_per_ms / urb_packs);
757 		ep->nurbs = min(max_urbs, urbs_per_period * periods_per_buffer);
758 	}
759 
760 	/* allocate and initialize data urbs */
761 	for (i = 0; i < ep->nurbs; i++) {
762 		struct snd_urb_ctx *u = &ep->urb[i];
763 		u->index = i;
764 		u->ep = ep;
765 		u->packets = urb_packs;
766 		u->buffer_size = maxsize * u->packets;
767 
768 		if (fmt->fmt_type == UAC_FORMAT_TYPE_II)
769 			u->packets++; /* for transfer delimiter */
770 		u->urb = usb_alloc_urb(u->packets, GFP_KERNEL);
771 		if (!u->urb)
772 			goto out_of_memory;
773 
774 		u->urb->transfer_buffer =
775 			usb_alloc_coherent(ep->chip->dev, u->buffer_size,
776 					   GFP_KERNEL, &u->urb->transfer_dma);
777 		if (!u->urb->transfer_buffer)
778 			goto out_of_memory;
779 		u->urb->pipe = ep->pipe;
780 		u->urb->transfer_flags = URB_NO_TRANSFER_DMA_MAP;
781 		u->urb->interval = 1 << ep->datainterval;
782 		u->urb->context = u;
783 		u->urb->complete = snd_complete_urb;
784 		INIT_LIST_HEAD(&u->ready_list);
785 	}
786 
787 	return 0;
788 
789 out_of_memory:
790 	release_urbs(ep, 0);
791 	return -ENOMEM;
792 }
793 
794 /*
795  * configure a sync endpoint
796  */
797 static int sync_ep_set_params(struct snd_usb_endpoint *ep)
798 {
799 	int i;
800 
801 	ep->syncbuf = usb_alloc_coherent(ep->chip->dev, SYNC_URBS * 4,
802 					 GFP_KERNEL, &ep->sync_dma);
803 	if (!ep->syncbuf)
804 		return -ENOMEM;
805 
806 	for (i = 0; i < SYNC_URBS; i++) {
807 		struct snd_urb_ctx *u = &ep->urb[i];
808 		u->index = i;
809 		u->ep = ep;
810 		u->packets = 1;
811 		u->urb = usb_alloc_urb(1, GFP_KERNEL);
812 		if (!u->urb)
813 			goto out_of_memory;
814 		u->urb->transfer_buffer = ep->syncbuf + i * 4;
815 		u->urb->transfer_dma = ep->sync_dma + i * 4;
816 		u->urb->transfer_buffer_length = 4;
817 		u->urb->pipe = ep->pipe;
818 		u->urb->transfer_flags = URB_NO_TRANSFER_DMA_MAP;
819 		u->urb->number_of_packets = 1;
820 		u->urb->interval = 1 << ep->syncinterval;
821 		u->urb->context = u;
822 		u->urb->complete = snd_complete_urb;
823 	}
824 
825 	ep->nurbs = SYNC_URBS;
826 
827 	return 0;
828 
829 out_of_memory:
830 	release_urbs(ep, 0);
831 	return -ENOMEM;
832 }
833 
834 /**
835  * snd_usb_endpoint_set_params: configure an snd_usb_endpoint
836  *
837  * @ep: the snd_usb_endpoint to configure
838  * @pcm_format: the audio fomat.
839  * @channels: the number of audio channels.
840  * @period_bytes: the number of bytes in one alsa period.
841  * @period_frames: the number of frames in one alsa period.
842  * @buffer_periods: the number of periods in one alsa buffer.
843  * @rate: the frame rate.
844  * @fmt: the USB audio format information
845  * @sync_ep: the sync endpoint to use, if any
846  *
847  * Determine the number of URBs to be used on this endpoint.
848  * An endpoint must be configured before it can be started.
849  * An endpoint that is already running can not be reconfigured.
850  */
851 int snd_usb_endpoint_set_params(struct snd_usb_endpoint *ep,
852 				snd_pcm_format_t pcm_format,
853 				unsigned int channels,
854 				unsigned int period_bytes,
855 				unsigned int period_frames,
856 				unsigned int buffer_periods,
857 				unsigned int rate,
858 				struct audioformat *fmt,
859 				struct snd_usb_endpoint *sync_ep)
860 {
861 	int err;
862 
863 	if (ep->use_count != 0) {
864 		usb_audio_warn(ep->chip,
865 			 "Unable to change format on ep #%x: already in use\n",
866 			 ep->ep_num);
867 		return -EBUSY;
868 	}
869 
870 	/* release old buffers, if any */
871 	release_urbs(ep, 0);
872 
873 	ep->datainterval = fmt->datainterval;
874 	ep->maxpacksize = fmt->maxpacksize;
875 	ep->fill_max = !!(fmt->attributes & UAC_EP_CS_ATTR_FILL_MAX);
876 
877 	if (snd_usb_get_speed(ep->chip->dev) == USB_SPEED_FULL)
878 		ep->freqn = get_usb_full_speed_rate(rate);
879 	else
880 		ep->freqn = get_usb_high_speed_rate(rate);
881 
882 	/* calculate the frequency in 16.16 format */
883 	ep->freqm = ep->freqn;
884 	ep->freqshift = INT_MIN;
885 
886 	ep->phase = 0;
887 
888 	switch (ep->type) {
889 	case  SND_USB_ENDPOINT_TYPE_DATA:
890 		err = data_ep_set_params(ep, pcm_format, channels,
891 					 period_bytes, period_frames,
892 					 buffer_periods, fmt, sync_ep);
893 		break;
894 	case  SND_USB_ENDPOINT_TYPE_SYNC:
895 		err = sync_ep_set_params(ep);
896 		break;
897 	default:
898 		err = -EINVAL;
899 	}
900 
901 	usb_audio_dbg(ep->chip,
902 		"Setting params for ep #%x (type %d, %d urbs), ret=%d\n",
903 		ep->ep_num, ep->type, ep->nurbs, err);
904 
905 	return err;
906 }
907 
908 /**
909  * snd_usb_endpoint_start: start an snd_usb_endpoint
910  *
911  * @ep: the endpoint to start
912  *
913  * A call to this function will increment the use count of the endpoint.
914  * In case it is not already running, the URBs for this endpoint will be
915  * submitted. Otherwise, this function does nothing.
916  *
917  * Must be balanced to calls of snd_usb_endpoint_stop().
918  *
919  * Returns an error if the URB submission failed, 0 in all other cases.
920  */
921 int snd_usb_endpoint_start(struct snd_usb_endpoint *ep)
922 {
923 	int err;
924 	unsigned int i;
925 
926 	if (atomic_read(&ep->chip->shutdown))
927 		return -EBADFD;
928 
929 	/* already running? */
930 	if (++ep->use_count != 1)
931 		return 0;
932 
933 	/* just to be sure */
934 	deactivate_urbs(ep, false);
935 
936 	ep->active_mask = 0;
937 	ep->unlink_mask = 0;
938 	ep->phase = 0;
939 
940 	snd_usb_endpoint_start_quirk(ep);
941 
942 	/*
943 	 * If this endpoint has a data endpoint as implicit feedback source,
944 	 * don't start the urbs here. Instead, mark them all as available,
945 	 * wait for the record urbs to return and queue the playback urbs
946 	 * from that context.
947 	 */
948 
949 	set_bit(EP_FLAG_RUNNING, &ep->flags);
950 
951 	if (snd_usb_endpoint_implicit_feedback_sink(ep)) {
952 		for (i = 0; i < ep->nurbs; i++) {
953 			struct snd_urb_ctx *ctx = ep->urb + i;
954 			list_add_tail(&ctx->ready_list, &ep->ready_playback_urbs);
955 		}
956 
957 		return 0;
958 	}
959 
960 	for (i = 0; i < ep->nurbs; i++) {
961 		struct urb *urb = ep->urb[i].urb;
962 
963 		if (snd_BUG_ON(!urb))
964 			goto __error;
965 
966 		if (usb_pipeout(ep->pipe)) {
967 			prepare_outbound_urb(ep, urb->context);
968 		} else {
969 			prepare_inbound_urb(ep, urb->context);
970 		}
971 
972 		err = usb_submit_urb(urb, GFP_ATOMIC);
973 		if (err < 0) {
974 			usb_audio_err(ep->chip,
975 				"cannot submit urb %d, error %d: %s\n",
976 				i, err, usb_error_string(err));
977 			goto __error;
978 		}
979 		set_bit(i, &ep->active_mask);
980 	}
981 
982 	return 0;
983 
984 __error:
985 	clear_bit(EP_FLAG_RUNNING, &ep->flags);
986 	ep->use_count--;
987 	deactivate_urbs(ep, false);
988 	return -EPIPE;
989 }
990 
991 /**
992  * snd_usb_endpoint_stop: stop an snd_usb_endpoint
993  *
994  * @ep: the endpoint to stop (may be NULL)
995  *
996  * A call to this function will decrement the use count of the endpoint.
997  * In case the last user has requested the endpoint stop, the URBs will
998  * actually be deactivated.
999  *
1000  * Must be balanced to calls of snd_usb_endpoint_start().
1001  *
1002  * The caller needs to synchronize the pending stop operation via
1003  * snd_usb_endpoint_sync_pending_stop().
1004  */
1005 void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep)
1006 {
1007 	if (!ep)
1008 		return;
1009 
1010 	if (snd_BUG_ON(ep->use_count == 0))
1011 		return;
1012 
1013 	if (--ep->use_count == 0) {
1014 		deactivate_urbs(ep, false);
1015 		set_bit(EP_FLAG_STOPPING, &ep->flags);
1016 	}
1017 }
1018 
1019 /**
1020  * snd_usb_endpoint_deactivate: deactivate an snd_usb_endpoint
1021  *
1022  * @ep: the endpoint to deactivate
1023  *
1024  * If the endpoint is not currently in use, this functions will
1025  * deactivate its associated URBs.
1026  *
1027  * In case of any active users, this functions does nothing.
1028  */
1029 void snd_usb_endpoint_deactivate(struct snd_usb_endpoint *ep)
1030 {
1031 	if (!ep)
1032 		return;
1033 
1034 	if (ep->use_count != 0)
1035 		return;
1036 
1037 	deactivate_urbs(ep, true);
1038 	wait_clear_urbs(ep);
1039 }
1040 
1041 /**
1042  * snd_usb_endpoint_release: Tear down an snd_usb_endpoint
1043  *
1044  * @ep: the endpoint to release
1045  *
1046  * This function does not care for the endpoint's use count but will tear
1047  * down all the streaming URBs immediately.
1048  */
1049 void snd_usb_endpoint_release(struct snd_usb_endpoint *ep)
1050 {
1051 	release_urbs(ep, 1);
1052 }
1053 
1054 /**
1055  * snd_usb_endpoint_free: Free the resources of an snd_usb_endpoint
1056  *
1057  * @ep: the endpoint to free
1058  *
1059  * This free all resources of the given ep.
1060  */
1061 void snd_usb_endpoint_free(struct snd_usb_endpoint *ep)
1062 {
1063 	kfree(ep);
1064 }
1065 
1066 /**
1067  * snd_usb_handle_sync_urb: parse an USB sync packet
1068  *
1069  * @ep: the endpoint to handle the packet
1070  * @sender: the sending endpoint
1071  * @urb: the received packet
1072  *
1073  * This function is called from the context of an endpoint that received
1074  * the packet and is used to let another endpoint object handle the payload.
1075  */
1076 void snd_usb_handle_sync_urb(struct snd_usb_endpoint *ep,
1077 			     struct snd_usb_endpoint *sender,
1078 			     const struct urb *urb)
1079 {
1080 	int shift;
1081 	unsigned int f;
1082 	unsigned long flags;
1083 
1084 	snd_BUG_ON(ep == sender);
1085 
1086 	/*
1087 	 * In case the endpoint is operating in implicit feedback mode, prepare
1088 	 * a new outbound URB that has the same layout as the received packet
1089 	 * and add it to the list of pending urbs. queue_pending_output_urbs()
1090 	 * will take care of them later.
1091 	 */
1092 	if (snd_usb_endpoint_implicit_feedback_sink(ep) &&
1093 	    ep->use_count != 0) {
1094 
1095 		/* implicit feedback case */
1096 		int i, bytes = 0;
1097 		struct snd_urb_ctx *in_ctx;
1098 		struct snd_usb_packet_info *out_packet;
1099 
1100 		in_ctx = urb->context;
1101 
1102 		/* Count overall packet size */
1103 		for (i = 0; i < in_ctx->packets; i++)
1104 			if (urb->iso_frame_desc[i].status == 0)
1105 				bytes += urb->iso_frame_desc[i].actual_length;
1106 
1107 		/*
1108 		 * skip empty packets. At least M-Audio's Fast Track Ultra stops
1109 		 * streaming once it received a 0-byte OUT URB
1110 		 */
1111 		if (bytes == 0)
1112 			return;
1113 
1114 		spin_lock_irqsave(&ep->lock, flags);
1115 		out_packet = ep->next_packet + ep->next_packet_write_pos;
1116 
1117 		/*
1118 		 * Iterate through the inbound packet and prepare the lengths
1119 		 * for the output packet. The OUT packet we are about to send
1120 		 * will have the same amount of payload bytes per stride as the
1121 		 * IN packet we just received. Since the actual size is scaled
1122 		 * by the stride, use the sender stride to calculate the length
1123 		 * in case the number of channels differ between the implicitly
1124 		 * fed-back endpoint and the synchronizing endpoint.
1125 		 */
1126 
1127 		out_packet->packets = in_ctx->packets;
1128 		for (i = 0; i < in_ctx->packets; i++) {
1129 			if (urb->iso_frame_desc[i].status == 0)
1130 				out_packet->packet_size[i] =
1131 					urb->iso_frame_desc[i].actual_length / sender->stride;
1132 			else
1133 				out_packet->packet_size[i] = 0;
1134 		}
1135 
1136 		ep->next_packet_write_pos++;
1137 		ep->next_packet_write_pos %= MAX_URBS;
1138 		spin_unlock_irqrestore(&ep->lock, flags);
1139 		queue_pending_output_urbs(ep);
1140 
1141 		return;
1142 	}
1143 
1144 	/*
1145 	 * process after playback sync complete
1146 	 *
1147 	 * Full speed devices report feedback values in 10.14 format as samples
1148 	 * per frame, high speed devices in 16.16 format as samples per
1149 	 * microframe.
1150 	 *
1151 	 * Because the Audio Class 1 spec was written before USB 2.0, many high
1152 	 * speed devices use a wrong interpretation, some others use an
1153 	 * entirely different format.
1154 	 *
1155 	 * Therefore, we cannot predict what format any particular device uses
1156 	 * and must detect it automatically.
1157 	 */
1158 
1159 	if (urb->iso_frame_desc[0].status != 0 ||
1160 	    urb->iso_frame_desc[0].actual_length < 3)
1161 		return;
1162 
1163 	f = le32_to_cpup(urb->transfer_buffer);
1164 	if (urb->iso_frame_desc[0].actual_length == 3)
1165 		f &= 0x00ffffff;
1166 	else
1167 		f &= 0x0fffffff;
1168 
1169 	if (f == 0)
1170 		return;
1171 
1172 	if (unlikely(sender->tenor_fb_quirk)) {
1173 		/*
1174 		 * Devices based on Tenor 8802 chipsets (TEAC UD-H01
1175 		 * and others) sometimes change the feedback value
1176 		 * by +/- 0x1.0000.
1177 		 */
1178 		if (f < ep->freqn - 0x8000)
1179 			f += 0xf000;
1180 		else if (f > ep->freqn + 0x8000)
1181 			f -= 0xf000;
1182 	} else if (unlikely(ep->freqshift == INT_MIN)) {
1183 		/*
1184 		 * The first time we see a feedback value, determine its format
1185 		 * by shifting it left or right until it matches the nominal
1186 		 * frequency value.  This assumes that the feedback does not
1187 		 * differ from the nominal value more than +50% or -25%.
1188 		 */
1189 		shift = 0;
1190 		while (f < ep->freqn - ep->freqn / 4) {
1191 			f <<= 1;
1192 			shift++;
1193 		}
1194 		while (f > ep->freqn + ep->freqn / 2) {
1195 			f >>= 1;
1196 			shift--;
1197 		}
1198 		ep->freqshift = shift;
1199 	} else if (ep->freqshift >= 0)
1200 		f <<= ep->freqshift;
1201 	else
1202 		f >>= -ep->freqshift;
1203 
1204 	if (likely(f >= ep->freqn - ep->freqn / 8 && f <= ep->freqmax)) {
1205 		/*
1206 		 * If the frequency looks valid, set it.
1207 		 * This value is referred to in prepare_playback_urb().
1208 		 */
1209 		spin_lock_irqsave(&ep->lock, flags);
1210 		ep->freqm = f;
1211 		spin_unlock_irqrestore(&ep->lock, flags);
1212 	} else {
1213 		/*
1214 		 * Out of range; maybe the shift value is wrong.
1215 		 * Reset it so that we autodetect again the next time.
1216 		 */
1217 		ep->freqshift = INT_MIN;
1218 	}
1219 }
1220 
1221