amdtp.c 19.2 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
/*
 * Audio and Music Data Transmission Protocol (IEC 61883-6) streams
 * with Common Isochronous Packet (IEC 61883-1) headers
 *
 * Copyright (c) Clemens Ladisch <clemens@ladisch.de>
 * Licensed under the terms of the GNU General Public License, version 2.
 */

#include <linux/device.h>
#include <linux/err.h>
#include <linux/firewire.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <sound/pcm.h>
#include "amdtp.h"

#define TICKS_PER_CYCLE		3072
#define CYCLES_PER_SECOND	8000
#define TICKS_PER_SECOND	(TICKS_PER_CYCLE * CYCLES_PER_SECOND)

#define TRANSFER_DELAY_TICKS	0x2e00 /* 479.17 µs */

23 24
/* isochronous header parameters */
#define ISO_DATA_LENGTH_SHIFT	16
25 26
#define TAG_CIP			1

27
/* common isochronous packet header parameters */
28
#define CIP_EOH			(1u << 31)
29
#define CIP_EOH_MASK		0x80000000
30
#define CIP_FMT_AM		(0x10 << 24)
31 32 33 34 35 36 37 38 39 40 41 42 43 44
#define CIP_FMT_MASK		0x3f000000
#define CIP_SYT_MASK		0x0000ffff
#define CIP_SYT_NO_INFO		0xffff
#define CIP_FDF_MASK		0x00ff0000
#define CIP_FDF_SFC_SHIFT	16

/*
 * Audio and Music transfer protocol specific parameters
 * only "Clock-based rate control mode" is supported
 */
#define AMDTP_FDF_AM824		(0 << (CIP_FDF_SFC_SHIFT + 3))
#define AMDTP_DBS_MASK		0x00ff0000
#define AMDTP_DBS_SHIFT		16
#define AMDTP_DBC_MASK		0x000000ff
45 46 47 48 49

/* TODO: make these configurable */
#define INTERRUPT_INTERVAL	16
#define QUEUE_LENGTH		48

50 51
static void pcm_period_tasklet(unsigned long data);

52
/**
53 54
 * amdtp_stream_init - initialize an AMDTP stream structure
 * @s: the AMDTP stream to initialize
55
 * @unit: the target of the stream
56
 * @dir: the direction of stream
57 58
 * @flags: the packet transmission method to use
 */
59
int amdtp_stream_init(struct amdtp_stream *s, struct fw_unit *unit,
60
		      enum amdtp_stream_direction dir, enum cip_flags flags)
61 62
{
	s->unit = fw_unit_get(unit);
63
	s->direction = dir;
64 65 66
	s->flags = flags;
	s->context = ERR_PTR(-1);
	mutex_init(&s->mutex);
67
	tasklet_init(&s->period_tasklet, pcm_period_tasklet, (unsigned long)s);
68
	s->packet_index = 0;
69 70 71

	return 0;
}
72
EXPORT_SYMBOL(amdtp_stream_init);
73 74

/**
75 76
 * amdtp_stream_destroy - free stream resources
 * @s: the AMDTP stream to destroy
77
 */
78
void amdtp_stream_destroy(struct amdtp_stream *s)
79
{
80
	WARN_ON(amdtp_stream_running(s));
81 82 83
	mutex_destroy(&s->mutex);
	fw_unit_put(s->unit);
}
84
EXPORT_SYMBOL(amdtp_stream_destroy);
85

86
const unsigned int amdtp_syt_intervals[CIP_SFC_COUNT] = {
87 88 89 90 91 92 93 94 95 96
	[CIP_SFC_32000]  =  8,
	[CIP_SFC_44100]  =  8,
	[CIP_SFC_48000]  =  8,
	[CIP_SFC_88200]  = 16,
	[CIP_SFC_96000]  = 16,
	[CIP_SFC_176400] = 32,
	[CIP_SFC_192000] = 32,
};
EXPORT_SYMBOL(amdtp_syt_intervals);

97
/**
98 99
 * amdtp_stream_set_parameters - set stream parameters
 * @s: the AMDTP stream to configure
100
 * @rate: the sample rate
101 102 103
 * @pcm_channels: the number of PCM samples in each data block, to be encoded
 *                as AM824 multi-bit linear audio
 * @midi_ports: the number of MIDI ports (i.e., MPX-MIDI Data Channels)
104
 *
105
 * The parameters must be set before the stream is started, and must not be
106 107
 * changed while the stream is running.
 */
108 109 110 111
void amdtp_stream_set_parameters(struct amdtp_stream *s,
				 unsigned int rate,
				 unsigned int pcm_channels,
				 unsigned int midi_ports)
112
{
113 114 115 116 117 118 119 120
	static const unsigned int rates[] = {
		[CIP_SFC_32000]  =  32000,
		[CIP_SFC_44100]  =  44100,
		[CIP_SFC_48000]  =  48000,
		[CIP_SFC_88200]  =  88200,
		[CIP_SFC_96000]  =  96000,
		[CIP_SFC_176400] = 176400,
		[CIP_SFC_192000] = 192000,
121 122 123
	};
	unsigned int sfc;

124
	if (WARN_ON(amdtp_stream_running(s)))
125 126
		return;

127 128
	for (sfc = 0; sfc < CIP_SFC_COUNT; ++sfc)
		if (rates[sfc] == rate)
129
			goto sfc_found;
130
	WARN_ON(1);
131 132 133
	return;

sfc_found:
134 135 136 137 138 139
	s->dual_wire = (s->flags & CIP_HI_DUALWIRE) && sfc > CIP_SFC_96000;
	if (s->dual_wire) {
		sfc -= 2;
		rate /= 2;
		pcm_channels *= 2;
	}
140
	s->sfc = sfc;
141 142 143 144 145
	s->data_block_quadlets = pcm_channels + DIV_ROUND_UP(midi_ports, 8);
	s->pcm_channels = pcm_channels;
	s->midi_ports = midi_ports;

	s->syt_interval = amdtp_syt_intervals[sfc];
146 147 148 149 150 151

	/* default buffering in the device */
	s->transfer_delay = TRANSFER_DELAY_TICKS - TICKS_PER_CYCLE;
	if (s->flags & CIP_BLOCKING)
		/* additional buffering needed to adjust for no-data packets */
		s->transfer_delay += TICKS_PER_SECOND * s->syt_interval / rate;
152
}
153
EXPORT_SYMBOL(amdtp_stream_set_parameters);
154 155

/**
156 157
 * amdtp_stream_get_max_payload - get the stream's packet size
 * @s: the AMDTP stream
158 159
 *
 * This function must not be called before the stream has been configured
160
 * with amdtp_stream_set_parameters().
161
 */
162
unsigned int amdtp_stream_get_max_payload(struct amdtp_stream *s)
163
{
164
	return 8 + s->syt_interval * s->data_block_quadlets * 4;
165
}
166
EXPORT_SYMBOL(amdtp_stream_get_max_payload);
167

168
static void amdtp_write_s16(struct amdtp_stream *s,
169 170
			    struct snd_pcm_substream *pcm,
			    __be32 *buffer, unsigned int frames);
171
static void amdtp_write_s32(struct amdtp_stream *s,
172 173
			    struct snd_pcm_substream *pcm,
			    __be32 *buffer, unsigned int frames);
174
static void amdtp_write_s16_dualwire(struct amdtp_stream *s,
175 176
				     struct snd_pcm_substream *pcm,
				     __be32 *buffer, unsigned int frames);
177
static void amdtp_write_s32_dualwire(struct amdtp_stream *s,
178 179
				     struct snd_pcm_substream *pcm,
				     __be32 *buffer, unsigned int frames);
180 181

/**
182 183
 * amdtp_stream_set_pcm_format - set the PCM format
 * @s: the AMDTP stream to configure
184 185
 * @format: the format of the ALSA PCM device
 *
186 187 188
 * The sample format must be set after the other paramters (rate/PCM channels/
 * MIDI) and before the stream is started, and must not be changed while the
 * stream is running.
189
 */
190 191
void amdtp_stream_set_pcm_format(struct amdtp_stream *s,
				 snd_pcm_format_t format)
192
{
193
	if (WARN_ON(amdtp_stream_running(s)))
194 195 196 197 198 199 200
		return;

	switch (format) {
	default:
		WARN_ON(1);
		/* fall through */
	case SNDRV_PCM_FORMAT_S16:
201 202 203 204
		if (s->dual_wire)
			s->transfer_samples = amdtp_write_s16_dualwire;
		else
			s->transfer_samples = amdtp_write_s16;
205 206
		break;
	case SNDRV_PCM_FORMAT_S32:
207 208 209 210
		if (s->dual_wire)
			s->transfer_samples = amdtp_write_s32_dualwire;
		else
			s->transfer_samples = amdtp_write_s32;
211 212 213
		break;
	}
}
214
EXPORT_SYMBOL(amdtp_stream_set_pcm_format);
215

216
/**
217 218
 * amdtp_stream_pcm_prepare - prepare PCM device for running
 * @s: the AMDTP stream
219 220 221
 *
 * This function should be called from the PCM device's .prepare callback.
 */
222
void amdtp_stream_pcm_prepare(struct amdtp_stream *s)
223 224 225 226
{
	tasklet_kill(&s->period_tasklet);
	s->pcm_buffer_pointer = 0;
	s->pcm_period_pointer = 0;
227
	s->pointer_flush = true;
228
}
229
EXPORT_SYMBOL(amdtp_stream_pcm_prepare);
230

231
static unsigned int calculate_data_blocks(struct amdtp_stream *s)
232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263
{
	unsigned int phase, data_blocks;

	if (!cip_sfc_is_base_44100(s->sfc)) {
		/* Sample_rate / 8000 is an integer, and precomputed. */
		data_blocks = s->data_block_state;
	} else {
		phase = s->data_block_state;

		/*
		 * This calculates the number of data blocks per packet so that
		 * 1) the overall rate is correct and exactly synchronized to
		 *    the bus clock, and
		 * 2) packets with a rounded-up number of blocks occur as early
		 *    as possible in the sequence (to prevent underruns of the
		 *    device's buffer).
		 */
		if (s->sfc == CIP_SFC_44100)
			/* 6 6 5 6 5 6 5 ... */
			data_blocks = 5 + ((phase & 1) ^
					   (phase == 0 || phase >= 40));
		else
			/* 12 11 11 11 11 ... or 23 22 22 22 22 ... */
			data_blocks = 11 * (s->sfc >> 1) + (phase == 0);
		if (++phase >= (80 >> (s->sfc >> 1)))
			phase = 0;
		s->data_block_state = phase;
	}

	return data_blocks;
}

264
static unsigned int calculate_syt(struct amdtp_stream *s,
265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295
				  unsigned int cycle)
{
	unsigned int syt_offset, phase, index, syt;

	if (s->last_syt_offset < TICKS_PER_CYCLE) {
		if (!cip_sfc_is_base_44100(s->sfc))
			syt_offset = s->last_syt_offset + s->syt_offset_state;
		else {
		/*
		 * The time, in ticks, of the n'th SYT_INTERVAL sample is:
		 *   n * SYT_INTERVAL * 24576000 / sample_rate
		 * Modulo TICKS_PER_CYCLE, the difference between successive
		 * elements is about 1386.23.  Rounding the results of this
		 * formula to the SYT precision results in a sequence of
		 * differences that begins with:
		 *   1386 1386 1387 1386 1386 1386 1387 1386 1386 1386 1387 ...
		 * This code generates _exactly_ the same sequence.
		 */
			phase = s->syt_offset_state;
			index = phase % 13;
			syt_offset = s->last_syt_offset;
			syt_offset += 1386 + ((index && !(index & 3)) ||
					      phase == 146);
			if (++phase >= 147)
				phase = 0;
			s->syt_offset_state = phase;
		}
	} else
		syt_offset = s->last_syt_offset - TICKS_PER_CYCLE;
	s->last_syt_offset = syt_offset;

296
	if (syt_offset < TICKS_PER_CYCLE) {
297
		syt_offset += s->transfer_delay;
298 299
		syt = (cycle + syt_offset / TICKS_PER_CYCLE) << 12;
		syt += syt_offset % TICKS_PER_CYCLE;
300

301
		return syt & CIP_SYT_MASK;
302
	} else {
303
		return CIP_SYT_NO_INFO;
304
	}
305 306
}

307
static void amdtp_write_s32(struct amdtp_stream *s,
308 309 310 311 312 313 314 315 316
			    struct snd_pcm_substream *pcm,
			    __be32 *buffer, unsigned int frames)
{
	struct snd_pcm_runtime *runtime = pcm->runtime;
	unsigned int channels, remaining_frames, frame_step, i, c;
	const u32 *src;

	channels = s->pcm_channels;
	src = (void *)runtime->dma_area +
317
			frames_to_bytes(runtime, s->pcm_buffer_pointer);
318 319 320 321 322 323 324 325 326 327 328 329 330 331 332
	remaining_frames = runtime->buffer_size - s->pcm_buffer_pointer;
	frame_step = s->data_block_quadlets - channels;

	for (i = 0; i < frames; ++i) {
		for (c = 0; c < channels; ++c) {
			*buffer = cpu_to_be32((*src >> 8) | 0x40000000);
			src++;
			buffer++;
		}
		buffer += frame_step;
		if (--remaining_frames == 0)
			src = (void *)runtime->dma_area;
	}
}

333
static void amdtp_write_s16(struct amdtp_stream *s,
334 335 336 337 338 339 340 341 342
			    struct snd_pcm_substream *pcm,
			    __be32 *buffer, unsigned int frames)
{
	struct snd_pcm_runtime *runtime = pcm->runtime;
	unsigned int channels, remaining_frames, frame_step, i, c;
	const u16 *src;

	channels = s->pcm_channels;
	src = (void *)runtime->dma_area +
343
			frames_to_bytes(runtime, s->pcm_buffer_pointer);
344 345 346 347 348 349 350 351 352 353 354 355 356 357 358
	remaining_frames = runtime->buffer_size - s->pcm_buffer_pointer;
	frame_step = s->data_block_quadlets - channels;

	for (i = 0; i < frames; ++i) {
		for (c = 0; c < channels; ++c) {
			*buffer = cpu_to_be32((*src << 8) | 0x40000000);
			src++;
			buffer++;
		}
		buffer += frame_step;
		if (--remaining_frames == 0)
			src = (void *)runtime->dma_area;
	}
}

359
static void amdtp_write_s32_dualwire(struct amdtp_stream *s,
360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389
				     struct snd_pcm_substream *pcm,
				     __be32 *buffer, unsigned int frames)
{
	struct snd_pcm_runtime *runtime = pcm->runtime;
	unsigned int channels, frame_adjust_1, frame_adjust_2, i, c;
	const u32 *src;

	channels = s->pcm_channels;
	src = (void *)runtime->dma_area +
			s->pcm_buffer_pointer * (runtime->frame_bits / 8);
	frame_adjust_1 = channels - 1;
	frame_adjust_2 = 1 - (s->data_block_quadlets - channels);

	channels /= 2;
	for (i = 0; i < frames; ++i) {
		for (c = 0; c < channels; ++c) {
			*buffer = cpu_to_be32((*src >> 8) | 0x40000000);
			src++;
			buffer += 2;
		}
		buffer -= frame_adjust_1;
		for (c = 0; c < channels; ++c) {
			*buffer = cpu_to_be32((*src >> 8) | 0x40000000);
			src++;
			buffer += 2;
		}
		buffer -= frame_adjust_2;
	}
}

390
static void amdtp_write_s16_dualwire(struct amdtp_stream *s,
391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420
				     struct snd_pcm_substream *pcm,
				     __be32 *buffer, unsigned int frames)
{
	struct snd_pcm_runtime *runtime = pcm->runtime;
	unsigned int channels, frame_adjust_1, frame_adjust_2, i, c;
	const u16 *src;

	channels = s->pcm_channels;
	src = (void *)runtime->dma_area +
			s->pcm_buffer_pointer * (runtime->frame_bits / 8);
	frame_adjust_1 = channels - 1;
	frame_adjust_2 = 1 - (s->data_block_quadlets - channels);

	channels /= 2;
	for (i = 0; i < frames; ++i) {
		for (c = 0; c < channels; ++c) {
			*buffer = cpu_to_be32((*src << 8) | 0x40000000);
			src++;
			buffer += 2;
		}
		buffer -= frame_adjust_1;
		for (c = 0; c < channels; ++c) {
			*buffer = cpu_to_be32((*src << 8) | 0x40000000);
			src++;
			buffer += 2;
		}
		buffer -= frame_adjust_2;
	}
}

421
static void amdtp_fill_pcm_silence(struct amdtp_stream *s,
422 423 424 425 426 427 428 429 430 431 432
				   __be32 *buffer, unsigned int frames)
{
	unsigned int i, c;

	for (i = 0; i < frames; ++i) {
		for (c = 0; c < s->pcm_channels; ++c)
			buffer[c] = cpu_to_be32(0x40000000);
		buffer += s->data_block_quadlets;
	}
}

433
static void amdtp_fill_midi(struct amdtp_stream *s,
434 435 436 437 438 439 440 441 442
			    __be32 *buffer, unsigned int frames)
{
	unsigned int i;

	for (i = 0; i < frames; ++i)
		buffer[s->pcm_channels + i * s->data_block_quadlets] =
						cpu_to_be32(0x80000000);
}

443
static void queue_out_packet(struct amdtp_stream *s, unsigned int cycle)
444 445
{
	__be32 *buffer;
446
	unsigned int index, data_blocks, syt, ptr;
447 448 449 450
	struct snd_pcm_substream *pcm;
	struct fw_iso_packet packet;
	int err;

451 452 453 454
	if (s->packet_index < 0)
		return;
	index = s->packet_index;

455
	/* this module generate empty packet for 'no data' */
456
	syt = calculate_syt(s, cycle);
457
	if (!(s->flags & CIP_BLOCKING))
458
		data_blocks = calculate_data_blocks(s);
459
	else if (syt != CIP_SYT_NO_INFO)
460 461 462
		data_blocks = s->syt_interval;
	else
		data_blocks = 0;
463

464
	buffer = s->buffer.packets[index].buffer;
465
	buffer[0] = cpu_to_be32(ACCESS_ONCE(s->source_node_id_field) |
466
				(s->data_block_quadlets << AMDTP_DBS_SHIFT) |
467 468
				s->data_block_counter);
	buffer[1] = cpu_to_be32(CIP_EOH | CIP_FMT_AM | AMDTP_FDF_AM824 |
469
				(s->sfc << CIP_FDF_SFC_SHIFT) | syt);
470 471 472 473 474 475 476 477 478 479 480 481 482
	buffer += 2;

	pcm = ACCESS_ONCE(s->pcm);
	if (pcm)
		s->transfer_samples(s, pcm, buffer, data_blocks);
	else
		amdtp_fill_pcm_silence(s, buffer, data_blocks);
	if (s->midi_ports)
		amdtp_fill_midi(s, buffer, data_blocks);

	s->data_block_counter = (s->data_block_counter + data_blocks) & 0xff;

	packet.payload_length = 8 + data_blocks * 4 * s->data_block_quadlets;
483
	packet.interrupt = IS_ALIGNED(index + 1, INTERRUPT_INTERVAL);
484 485 486 487 488 489
	packet.skip = 0;
	packet.tag = TAG_CIP;
	packet.sy = 0;
	packet.header_length = 0;

	err = fw_iso_context_queue(s->context, &packet, &s->buffer.iso_buffer,
490 491
				   s->buffer.packets[index].offset);
	if (err < 0) {
492
		dev_err(&s->unit->device, "queueing error: %d\n", err);
493
		s->packet_index = -1;
494
		amdtp_stream_pcm_abort(s);
495 496
		return;
	}
497

498 499 500
	if (++index >= QUEUE_LENGTH)
		index = 0;
	s->packet_index = index;
501 502

	if (pcm) {
503 504 505
		if (s->dual_wire)
			data_blocks *= 2;

506 507 508 509 510 511 512 513
		ptr = s->pcm_buffer_pointer + data_blocks;
		if (ptr >= pcm->runtime->buffer_size)
			ptr -= pcm->runtime->buffer_size;
		ACCESS_ONCE(s->pcm_buffer_pointer) = ptr;

		s->pcm_period_pointer += data_blocks;
		if (s->pcm_period_pointer >= pcm->runtime->period_size) {
			s->pcm_period_pointer -= pcm->runtime->period_size;
514
			s->pointer_flush = false;
515
			tasklet_hi_schedule(&s->period_tasklet);
516 517 518 519
		}
	}
}

520 521
static void pcm_period_tasklet(unsigned long data)
{
522
	struct amdtp_stream *s = (void *)data;
523 524 525 526 527 528
	struct snd_pcm_substream *pcm = ACCESS_ONCE(s->pcm);

	if (pcm)
		snd_pcm_period_elapsed(pcm);
}

529
static void out_packet_callback(struct fw_iso_context *context, u32 cycle,
530
			size_t header_length, void *header, void *private_data)
531
{
532
	struct amdtp_stream *s = private_data;
533 534 535 536 537 538 539 540 541 542 543
	unsigned int i, packets = header_length / 4;

	/*
	 * Compute the cycle of the last queued packet.
	 * (We need only the four lowest bits for the SYT, so we can ignore
	 * that bits 0-11 must wrap around at 3072.)
	 */
	cycle += QUEUE_LENGTH - packets;

	for (i = 0; i < packets; ++i)
		queue_out_packet(s, ++cycle);
544
	fw_iso_context_queue_flush(s->context);
545 546
}

547
static int queue_initial_skip_packets(struct amdtp_stream *s)
548 549 550 551 552 553 554 555
{
	struct fw_iso_packet skip_packet = {
		.skip = 1,
	};
	unsigned int i;
	int err;

	for (i = 0; i < QUEUE_LENGTH; ++i) {
556
		skip_packet.interrupt = IS_ALIGNED(s->packet_index + 1,
557 558 559 560
						   INTERRUPT_INTERVAL);
		err = fw_iso_context_queue(s->context, &skip_packet, NULL, 0);
		if (err < 0)
			return err;
561 562
		if (++s->packet_index >= QUEUE_LENGTH)
			s->packet_index = 0;
563 564 565 566 567 568
	}

	return 0;
}

/**
569 570
 * amdtp_stream_start - start transferring packets
 * @s: the AMDTP stream to start
571 572 573 574
 * @channel: the isochronous channel on the bus
 * @speed: firewire speed code
 *
 * The stream cannot be started until it has been configured with
575 576
 * amdtp_stream_set_parameters() and it must be started before any PCM or MIDI
 * device can be started.
577
 */
578
int amdtp_stream_start(struct amdtp_stream *s, int channel, int speed)
579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595
{
	static const struct {
		unsigned int data_block;
		unsigned int syt_offset;
	} initial_state[] = {
		[CIP_SFC_32000]  = {  4, 3072 },
		[CIP_SFC_48000]  = {  6, 1024 },
		[CIP_SFC_96000]  = { 12, 1024 },
		[CIP_SFC_192000] = { 24, 1024 },
		[CIP_SFC_44100]  = {  0,   67 },
		[CIP_SFC_88200]  = {  0,   67 },
		[CIP_SFC_176400] = {  0,   67 },
	};
	int err;

	mutex_lock(&s->mutex);

596
	if (WARN_ON(amdtp_stream_running(s) ||
597 598 599 600 601 602 603 604 605 606
		    (!s->pcm_channels && !s->midi_ports))) {
		err = -EBADFD;
		goto err_unlock;
	}

	s->data_block_state = initial_state[s->sfc].data_block;
	s->syt_offset_state = initial_state[s->sfc].syt_offset;
	s->last_syt_offset = TICKS_PER_CYCLE;

	err = iso_packets_buffer_init(&s->buffer, s->unit, QUEUE_LENGTH,
607
				      amdtp_stream_get_max_payload(s),
608 609 610 611 612 613 614 615 616 617 618 619
				      DMA_TO_DEVICE);
	if (err < 0)
		goto err_unlock;

	s->context = fw_iso_context_create(fw_parent_device(s->unit)->card,
					   FW_ISO_CONTEXT_TRANSMIT,
					   channel, speed, 0,
					   out_packet_callback, s);
	if (IS_ERR(s->context)) {
		err = PTR_ERR(s->context);
		if (err == -EBUSY)
			dev_err(&s->unit->device,
620
				"no free stream on this controller\n");
621 622 623
		goto err_buffer;
	}

624
	amdtp_stream_update(s);
625

626
	s->packet_index = 0;
627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649
	s->data_block_counter = 0;
	err = queue_initial_skip_packets(s);
	if (err < 0)
		goto err_context;

	err = fw_iso_context_start(s->context, -1, 0, 0);
	if (err < 0)
		goto err_context;

	mutex_unlock(&s->mutex);

	return 0;

err_context:
	fw_iso_context_destroy(s->context);
	s->context = ERR_PTR(-1);
err_buffer:
	iso_packets_buffer_destroy(&s->buffer, s->unit);
err_unlock:
	mutex_unlock(&s->mutex);

	return err;
}
650
EXPORT_SYMBOL(amdtp_stream_start);
651

652
/**
653 654
 * amdtp_stream_pcm_pointer - get the PCM buffer position
 * @s: the AMDTP stream that transports the PCM data
655 656 657
 *
 * Returns the current buffer position, in frames.
 */
658
unsigned long amdtp_stream_pcm_pointer(struct amdtp_stream *s)
659
{
660 661 662 663 664
	/* this optimization is allowed to be racy */
	if (s->pointer_flush)
		fw_iso_context_flush_completions(s->context);
	else
		s->pointer_flush = true;
665 666 667

	return ACCESS_ONCE(s->pcm_buffer_pointer);
}
668
EXPORT_SYMBOL(amdtp_stream_pcm_pointer);
669

670
/**
671 672
 * amdtp_stream_update - update the stream after a bus reset
 * @s: the AMDTP stream
673
 */
674
void amdtp_stream_update(struct amdtp_stream *s)
675 676 677 678
{
	ACCESS_ONCE(s->source_node_id_field) =
		(fw_parent_device(s->unit)->card->node_id & 0x3f) << 24;
}
679
EXPORT_SYMBOL(amdtp_stream_update);
680 681

/**
682 683
 * amdtp_stream_stop - stop sending packets
 * @s: the AMDTP stream to stop
684 685 686 687
 *
 * All PCM and MIDI devices of the stream must be stopped before the stream
 * itself can be stopped.
 */
688
void amdtp_stream_stop(struct amdtp_stream *s)
689 690 691
{
	mutex_lock(&s->mutex);

692
	if (!amdtp_stream_running(s)) {
693 694 695 696
		mutex_unlock(&s->mutex);
		return;
	}

697
	tasklet_kill(&s->period_tasklet);
698 699 700 701 702 703 704
	fw_iso_context_stop(s->context);
	fw_iso_context_destroy(s->context);
	s->context = ERR_PTR(-1);
	iso_packets_buffer_destroy(&s->buffer, s->unit);

	mutex_unlock(&s->mutex);
}
705
EXPORT_SYMBOL(amdtp_stream_stop);
706 707

/**
708
 * amdtp_stream_pcm_abort - abort the running PCM device
709 710 711 712 713
 * @s: the AMDTP stream about to be stopped
 *
 * If the isochronous stream needs to be stopped asynchronously, call this
 * function first to stop the PCM device.
 */
714
void amdtp_stream_pcm_abort(struct amdtp_stream *s)
715 716 717 718 719 720 721 722 723 724 725
{
	struct snd_pcm_substream *pcm;

	pcm = ACCESS_ONCE(s->pcm);
	if (pcm) {
		snd_pcm_stream_lock_irq(pcm);
		if (snd_pcm_running(pcm))
			snd_pcm_stop(pcm, SNDRV_PCM_STATE_XRUN);
		snd_pcm_stream_unlock_irq(pcm);
	}
}
726
EXPORT_SYMBOL(amdtp_stream_pcm_abort);