linux/sound/drivers/pcm-indirect2.c
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   1/*
   2 * Helper functions for indirect PCM data transfer to a simple FIFO in
   3 * hardware (small, no possibility to read "hardware io position",
   4 * updating position done by interrupt, ...)
   5 *
   6 *  Copyright (c) by 2007  Joachim Foerster <JOFT@gmx.de>
   7 *
   8 *  Based on "pcm-indirect.h" (alsa-driver-1.0.13) by
   9 *
  10 *  Copyright (c) by Takashi Iwai <tiwai@suse.de>
  11 *                   Jaroslav Kysela <perex@suse.cz>
  12 *
  13 *   This program is free software; you can redistribute it and/or modify
  14 *   it under the terms of the GNU General Public License as published by
  15 *   the Free Software Foundation; either version 2 of the License, or
  16 *   (at your option) any later version.
  17 *
  18 *   This program is distributed in the hope that it will be useful,
  19 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
  20 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21 *   GNU General Public License for more details.
  22 *
  23 *   You should have received a copy of the GNU General Public License
  24 *   along with this program; if not, write to the Free Software
  25 *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  26 */
  27
  28/* snd_printk/d() */
  29#include <sound/core.h>
  30/* struct snd_pcm_substream, struct snd_pcm_runtime, snd_pcm_uframes_t
  31 * snd_pcm_period_elapsed() */
  32#include <sound/pcm.h>
  33
  34#include "pcm-indirect2.h"
  35
  36#ifdef SND_PCM_INDIRECT2_STAT
  37/* jiffies */
  38#include <linux/jiffies.h>
  39
  40void snd_pcm_indirect2_stat(struct snd_pcm_substream *substream,
  41                            struct snd_pcm_indirect2 *rec)
  42{
  43        struct snd_pcm_runtime *runtime = substream->runtime;
  44        int i;
  45        int j;
  46        int k;
  47        int seconds = (rec->lastbytetime - rec->firstbytetime) / HZ;
  48
  49        snd_printk(KERN_DEBUG "STAT: mul_elapsed: %u, mul_elapsed_real: %d, "
  50                   "irq_occured: %d\n",
  51                   rec->mul_elapsed, rec->mul_elapsed_real, rec->irq_occured);
  52        snd_printk(KERN_DEBUG "STAT: min_multiple: %d (irqs/period)\n",
  53                   rec->min_multiple);
  54        snd_printk(KERN_DEBUG "STAT: firstbytetime: %lu, lastbytetime: %lu, "
  55                   "firstzerotime: %lu\n",
  56                 rec->firstbytetime, rec->lastbytetime, rec->firstzerotime);
  57        snd_printk(KERN_DEBUG "STAT: bytes2hw: %u Bytes => (by runtime->rate) "
  58                   "length: %d s\n",
  59                 rec->bytes2hw, rec->bytes2hw / 2 / 2 / runtime->rate);
  60        snd_printk(KERN_DEBUG "STAT: (by measurement) length: %d => "
  61                   "rate: %d Bytes/s = %d Frames/s|Hz\n",
  62                   seconds, rec->bytes2hw / seconds,
  63                   rec->bytes2hw / 2 / 2 / seconds);
  64        snd_printk(KERN_DEBUG
  65                   "STAT: zeros2hw: %u = %d ms ~ %d * %d zero copies\n",
  66                   rec->zeros2hw, ((rec->zeros2hw / 2 / 2) * 1000) /
  67                   runtime->rate,
  68                   rec->zeros2hw / (rec->hw_buffer_size / 2),
  69                   (rec->hw_buffer_size / 2));
  70        snd_printk(KERN_DEBUG "STAT: pointer_calls: %u, lastdifftime: %u\n",
  71                   rec->pointer_calls, rec->lastdifftime);
  72        snd_printk(KERN_DEBUG "STAT: sw_io: %d, sw_data: %d\n", rec->sw_io,
  73                   rec->sw_data);
  74        snd_printk(KERN_DEBUG "STAT: byte_sizes[]:\n");
  75        k = 0;
  76        for (j = 0; j < 8; j++) {
  77                for (i = j * 8; i < (j + 1) * 8; i++)
  78                        if (rec->byte_sizes[i] != 0) {
  79                                snd_printk(KERN_DEBUG "%u: %u",
  80                                           i, rec->byte_sizes[i]);
  81                                k++;
  82                        }
  83                if (((k % 8) == 0) && (k != 0)) {
  84                        snd_printk(KERN_DEBUG "\n");
  85                        k = 0;
  86                }
  87        }
  88        snd_printk(KERN_DEBUG "\n");
  89        snd_printk(KERN_DEBUG "STAT: zero_sizes[]:\n");
  90        for (j = 0; j < 8; j++) {
  91                k = 0;
  92                for (i = j * 8; i < (j + 1) * 8; i++)
  93                        if (rec->zero_sizes[i] != 0)
  94                                snd_printk(KERN_DEBUG "%u: %u",
  95                                           i, rec->zero_sizes[i]);
  96                        else
  97                                k++;
  98                if (!k)
  99                        snd_printk(KERN_DEBUG "\n");
 100        }
 101        snd_printk(KERN_DEBUG "\n");
 102        snd_printk(KERN_DEBUG "STAT: min_adds[]:\n");
 103        for (j = 0; j < 8; j++) {
 104                if (rec->min_adds[j] != 0)
 105                        snd_printk(KERN_DEBUG "%u: %u", j, rec->min_adds[j]);
 106        }
 107        snd_printk(KERN_DEBUG "\n");
 108        snd_printk(KERN_DEBUG "STAT: mul_adds[]:\n");
 109        for (j = 0; j < 8; j++) {
 110                if (rec->mul_adds[j] != 0)
 111                        snd_printk(KERN_DEBUG "%u: %u", j, rec->mul_adds[j]);
 112        }
 113        snd_printk(KERN_DEBUG "\n");
 114        snd_printk(KERN_DEBUG
 115                   "STAT: zero_times_saved: %d, zero_times_notsaved: %d\n",
 116                   rec->zero_times_saved, rec->zero_times_notsaved);
 117        /* snd_printk(KERN_DEBUG "STAT: zero_times[]\n");
 118        i = 0;
 119        for (j = 0; j < 3750; j++) {
 120                if (rec->zero_times[j] != 0) {
 121                        snd_printk(KERN_DEBUG "%u: %u", j, rec->zero_times[j]);
 122                        i++;
 123                }
 124                if (((i % 8) == 0) && (i != 0))
 125                        snd_printk(KERN_DEBUG "\n");
 126        }
 127        snd_printk(KERN_DEBUG "\n"); */
 128        return;
 129}
 130#endif
 131
 132/*
 133 * _internal_ helper function for playback/capture transfer function
 134 */
 135static void
 136snd_pcm_indirect2_increase_min_periods(struct snd_pcm_substream *substream,
 137                                       struct snd_pcm_indirect2 *rec,
 138                                       int isplay, int iscopy,
 139                                       unsigned int bytes)
 140{
 141        if (rec->min_periods >= 0) {
 142                if (iscopy) {
 143                        rec->sw_io += bytes;
 144                        if (rec->sw_io >= rec->sw_buffer_size)
 145                                rec->sw_io -= rec->sw_buffer_size;
 146                } else if (isplay) {
 147                        /* If application does not write data in multiples of
 148                         * a period, move sw_data to the next correctly aligned
 149                         * position, so that sw_io can converge to it (in the
 150                         * next step).
 151                         */
 152                        if (!rec->check_alignment) {
 153                                if (rec->bytes2hw %
 154                                    snd_pcm_lib_period_bytes(substream)) {
 155                                        unsigned bytes2hw_aligned =
 156                                            (1 +
 157                                             (rec->bytes2hw /
 158                                              snd_pcm_lib_period_bytes
 159                                              (substream))) *
 160                                            snd_pcm_lib_period_bytes
 161                                            (substream);
 162                                        rec->sw_data =
 163                                            bytes2hw_aligned %
 164                                            rec->sw_buffer_size;
 165#ifdef SND_PCM_INDIRECT2_STAT
 166                                        snd_printk(KERN_DEBUG
 167                                                   "STAT: @re-align: aligned "
 168                                                   "bytes2hw to next period "
 169                                                   "size boundary: %d "
 170                                                   "(instead of %d)\n",
 171                                                   bytes2hw_aligned,
 172                                                   rec->bytes2hw);
 173                                        snd_printk(KERN_DEBUG
 174                                                   "STAT: @re-align: sw_data "
 175                                                   "moves to: %d\n",
 176                                                   rec->sw_data);
 177#endif
 178                                }
 179                                rec->check_alignment = 1;
 180                        }
 181                        /* We are at the end and are copying zeros into the
 182                         * fifo.
 183                         * Now, we have to make sure that sw_io is increased
 184                         * until the position of sw_data: Filling the fifo with
 185                         * the first zeros means, the last bytes were played.
 186                         */
 187                        if (rec->sw_io != rec->sw_data) {
 188                                unsigned int diff;
 189                                if (rec->sw_data > rec->sw_io)
 190                                        diff = rec->sw_data - rec->sw_io;
 191                                else
 192                                        diff = (rec->sw_buffer_size -
 193                                                rec->sw_io) +
 194                                                rec->sw_data;
 195                                if (bytes >= diff)
 196                                        rec->sw_io = rec->sw_data;
 197                                else {
 198                                        rec->sw_io += bytes;
 199                                        if (rec->sw_io >= rec->sw_buffer_size)
 200                                                rec->sw_io -=
 201                                                    rec->sw_buffer_size;
 202                                }
 203                        }
 204                }
 205                rec->min_period_count += bytes;
 206                if (rec->min_period_count >= (rec->hw_buffer_size / 2)) {
 207                        rec->min_periods += (rec->min_period_count /
 208                                             (rec->hw_buffer_size / 2));
 209#ifdef SND_PCM_INDIRECT2_STAT
 210                        if ((rec->min_period_count /
 211                             (rec->hw_buffer_size / 2)) > 7)
 212                                snd_printk(KERN_DEBUG
 213                                           "STAT: more than 7 (%d) min_adds "
 214                                           "at once - too big to save!\n",
 215                                           (rec->min_period_count /
 216                                            (rec->hw_buffer_size / 2)));
 217                        else
 218                                rec->min_adds[(rec->min_period_count /
 219                                               (rec->hw_buffer_size / 2))]++;
 220#endif
 221                        rec->min_period_count = (rec->min_period_count %
 222                                                 (rec->hw_buffer_size / 2));
 223                }
 224        } else if (isplay && iscopy)
 225                rec->min_periods = 0;
 226}
 227
 228/*
 229 * helper function for playback/capture pointer callback
 230 */
 231snd_pcm_uframes_t
 232snd_pcm_indirect2_pointer(struct snd_pcm_substream *substream,
 233                          struct snd_pcm_indirect2 *rec)
 234{
 235#ifdef SND_PCM_INDIRECT2_STAT
 236        rec->pointer_calls++;
 237#endif
 238        return bytes_to_frames(substream->runtime, rec->sw_io);
 239}
 240
 241/*
 242 * _internal_ helper function for playback interrupt callback
 243 */
 244static void
 245snd_pcm_indirect2_playback_transfer(struct snd_pcm_substream *substream,
 246                                    struct snd_pcm_indirect2 *rec,
 247                                    snd_pcm_indirect2_copy_t copy,
 248                                    snd_pcm_indirect2_zero_t zero)
 249{
 250        struct snd_pcm_runtime *runtime = substream->runtime;
 251        snd_pcm_uframes_t appl_ptr = runtime->control->appl_ptr;
 252
 253        /* runtime->control->appl_ptr: position where ALSA will write next time
 254         * rec->appl_ptr: position where ALSA was last time
 255         * diff: obviously ALSA wrote that much bytes into the intermediate
 256         * buffer since we checked last time
 257         */
 258        snd_pcm_sframes_t diff = appl_ptr - rec->appl_ptr;
 259
 260        if (diff) {
 261#ifdef SND_PCM_INDIRECT2_STAT
 262                rec->lastdifftime = jiffies;
 263#endif
 264                if (diff < -(snd_pcm_sframes_t) (runtime->boundary / 2))
 265                        diff += runtime->boundary;
 266                /* number of bytes "added" by ALSA increases the number of
 267                 * bytes which are ready to "be transferred to HW"/"played"
 268                 * Then, set rec->appl_ptr to not count bytes twice next time.
 269                 */
 270                rec->sw_ready += (int)frames_to_bytes(runtime, diff);
 271                rec->appl_ptr = appl_ptr;
 272        }
 273        if (rec->hw_ready && (rec->sw_ready <= 0)) {
 274                unsigned int bytes;
 275
 276#ifdef SND_PCM_INDIRECT2_STAT
 277                if (rec->firstzerotime == 0) {
 278                        rec->firstzerotime = jiffies;
 279                        snd_printk(KERN_DEBUG
 280                                   "STAT: @firstzerotime: mul_elapsed: %d, "
 281                                   "min_period_count: %d\n",
 282                                   rec->mul_elapsed, rec->min_period_count);
 283                        snd_printk(KERN_DEBUG
 284                                   "STAT: @firstzerotime: sw_io: %d, "
 285                                   "sw_data: %d, appl_ptr: %u\n",
 286                                   rec->sw_io, rec->sw_data,
 287                                   (unsigned int)appl_ptr);
 288                }
 289                if ((jiffies - rec->firstzerotime) < 3750) {
 290                        rec->zero_times[(jiffies - rec->firstzerotime)]++;
 291                        rec->zero_times_saved++;
 292                } else
 293                        rec->zero_times_notsaved++;
 294#endif
 295                bytes = zero(substream, rec);
 296
 297#ifdef SND_PCM_INDIRECT2_STAT
 298                rec->zeros2hw += bytes;
 299                if (bytes < 64)
 300                        rec->zero_sizes[bytes]++;
 301                else
 302                        snd_printk(KERN_DEBUG
 303                                   "STAT: %d zero Bytes copied to hardware at "
 304                                   "once - too big to save!\n",
 305                                   bytes);
 306#endif
 307                snd_pcm_indirect2_increase_min_periods(substream, rec, 1, 0,
 308                                                       bytes);
 309                return;
 310        }
 311        while (rec->hw_ready && (rec->sw_ready > 0)) {
 312                /* sw_to_end: max. number of bytes that can be read/take from
 313                 * the current position (sw_data) in _one_ step
 314                 */
 315                unsigned int sw_to_end = rec->sw_buffer_size - rec->sw_data;
 316
 317                /* bytes: number of bytes we have available (for reading) */
 318                unsigned int bytes = rec->sw_ready;
 319
 320                if (sw_to_end < bytes)
 321                        bytes = sw_to_end;
 322                if (!bytes)
 323                        break;
 324
 325#ifdef SND_PCM_INDIRECT2_STAT
 326                if (rec->firstbytetime == 0)
 327                        rec->firstbytetime = jiffies;
 328                rec->lastbytetime = jiffies;
 329#endif
 330                /* copy bytes from intermediate buffer position sw_data to the
 331                 * HW and return number of bytes actually written
 332                 * Furthermore, set hw_ready to 0, if the fifo isn't empty
 333                 * now => more could be transferred to fifo
 334                 */
 335                bytes = copy(substream, rec, bytes);
 336                rec->bytes2hw += bytes;
 337
 338#ifdef SND_PCM_INDIRECT2_STAT
 339                if (bytes < 64)
 340                        rec->byte_sizes[bytes]++;
 341                else
 342                        snd_printk(KERN_DEBUG
 343                                   "STAT: %d Bytes copied to hardware at once "
 344                                   "- too big to save!\n",
 345                                   bytes);
 346#endif
 347                /* increase sw_data by the number of actually written bytes
 348                 * (= number of taken bytes from intermediate buffer)
 349                 */
 350                rec->sw_data += bytes;
 351                if (rec->sw_data == rec->sw_buffer_size)
 352                        rec->sw_data = 0;
 353                /* now sw_data is the position where ALSA is going to write
 354                 * in the intermediate buffer next time = position we are going
 355                 * to read from next time
 356                 */
 357
 358                snd_pcm_indirect2_increase_min_periods(substream, rec, 1, 1,
 359                                                       bytes);
 360
 361                /* we read bytes from intermediate buffer, so we need to say
 362                 * that the number of bytes ready for transfer are decreased
 363                 * now
 364                 */
 365                rec->sw_ready -= bytes;
 366        }
 367        return;
 368}
 369
 370/*
 371 * helper function for playback interrupt routine
 372 */
 373void
 374snd_pcm_indirect2_playback_interrupt(struct snd_pcm_substream *substream,
 375                                     struct snd_pcm_indirect2 *rec,
 376                                     snd_pcm_indirect2_copy_t copy,
 377                                     snd_pcm_indirect2_zero_t zero)
 378{
 379#ifdef SND_PCM_INDIRECT2_STAT
 380        rec->irq_occured++;
 381#endif
 382        /* hardware played some bytes, so there is room again (in fifo) */
 383        rec->hw_ready = 1;
 384
 385        /* don't call ack() now, instead call transfer() function directly
 386         * (normally called by ack() )
 387         */
 388        snd_pcm_indirect2_playback_transfer(substream, rec, copy, zero);
 389
 390        if (rec->min_periods >= rec->min_multiple) {
 391#ifdef SND_PCM_INDIRECT2_STAT
 392                if ((rec->min_periods / rec->min_multiple) > 7)
 393                        snd_printk(KERN_DEBUG
 394                                   "STAT: more than 7 (%d) mul_adds - too big "
 395                                   "to save!\n",
 396                                   (rec->min_periods / rec->min_multiple));
 397                else
 398                        rec->mul_adds[(rec->min_periods /
 399                                       rec->min_multiple)]++;
 400                rec->mul_elapsed_real += (rec->min_periods /
 401                                          rec->min_multiple);
 402                rec->mul_elapsed++;
 403#endif
 404                rec->min_periods = (rec->min_periods % rec->min_multiple);
 405                snd_pcm_period_elapsed(substream);
 406        }
 407}
 408
 409/*
 410 * _internal_ helper function for capture interrupt callback
 411 */
 412static void
 413snd_pcm_indirect2_capture_transfer(struct snd_pcm_substream *substream,
 414                                   struct snd_pcm_indirect2 *rec,
 415                                   snd_pcm_indirect2_copy_t copy,
 416                                   snd_pcm_indirect2_zero_t null)
 417{
 418        struct snd_pcm_runtime *runtime = substream->runtime;
 419        snd_pcm_uframes_t appl_ptr = runtime->control->appl_ptr;
 420        snd_pcm_sframes_t diff = appl_ptr - rec->appl_ptr;
 421
 422        if (diff) {
 423#ifdef SND_PCM_INDIRECT2_STAT
 424                rec->lastdifftime = jiffies;
 425#endif
 426                if (diff < -(snd_pcm_sframes_t) (runtime->boundary / 2))
 427                        diff += runtime->boundary;
 428                rec->sw_ready -= frames_to_bytes(runtime, diff);
 429                rec->appl_ptr = appl_ptr;
 430        }
 431        /* if hardware has something, but the intermediate buffer is full
 432         * => skip contents of buffer
 433         */
 434        if (rec->hw_ready && (rec->sw_ready >= (int)rec->sw_buffer_size)) {
 435                unsigned int bytes;
 436
 437#ifdef SND_PCM_INDIRECT2_STAT
 438                if (rec->firstzerotime == 0) {
 439                        rec->firstzerotime = jiffies;
 440                        snd_printk(KERN_DEBUG "STAT: (capture) "
 441                                   "@firstzerotime: mul_elapsed: %d, "
 442                                   "min_period_count: %d\n",
 443                                   rec->mul_elapsed, rec->min_period_count);
 444                        snd_printk(KERN_DEBUG "STAT: (capture) "
 445                                   "@firstzerotime: sw_io: %d, sw_data: %d, "
 446                                   "appl_ptr: %u\n",
 447                                   rec->sw_io, rec->sw_data,
 448                                   (unsigned int)appl_ptr);
 449                }
 450                if ((jiffies - rec->firstzerotime) < 3750) {
 451                        rec->zero_times[(jiffies - rec->firstzerotime)]++;
 452                        rec->zero_times_saved++;
 453                } else
 454                        rec->zero_times_notsaved++;
 455#endif
 456                bytes = null(substream, rec);
 457
 458#ifdef SND_PCM_INDIRECT2_STAT
 459                rec->zeros2hw += bytes;
 460                if (bytes < 64)
 461                        rec->zero_sizes[bytes]++;
 462                else
 463                        snd_printk(KERN_DEBUG
 464                                   "STAT: (capture) %d zero Bytes copied to "
 465                                   "hardware at once - too big to save!\n",
 466                                   bytes);
 467#endif
 468                snd_pcm_indirect2_increase_min_periods(substream, rec, 0, 0,
 469                                                       bytes);
 470                /* report an overrun */
 471                rec->sw_io = SNDRV_PCM_POS_XRUN;
 472                return;
 473        }
 474        while (rec->hw_ready && (rec->sw_ready < (int)rec->sw_buffer_size)) {
 475                /* sw_to_end: max. number of bytes that we can write to the
 476                 *  intermediate buffer (until it's end)
 477                 */
 478                size_t sw_to_end = rec->sw_buffer_size - rec->sw_data;
 479
 480                /* bytes: max. number of bytes, which may be copied to the
 481                 *  intermediate buffer without overflow (in _one_ step)
 482                 */
 483                size_t bytes = rec->sw_buffer_size - rec->sw_ready;
 484
 485                /* limit number of bytes (for transfer) by available room in
 486                 * the intermediate buffer
 487                 */
 488                if (sw_to_end < bytes)
 489                        bytes = sw_to_end;
 490                if (!bytes)
 491                        break;
 492
 493#ifdef SND_PCM_INDIRECT2_STAT
 494                if (rec->firstbytetime == 0)
 495                        rec->firstbytetime = jiffies;
 496                rec->lastbytetime = jiffies;
 497#endif
 498                /* copy bytes from the intermediate buffer (position sw_data)
 499                 * to the HW at most and return number of bytes actually copied
 500                 * from HW
 501                 * Furthermore, set hw_ready to 0, if the fifo is empty now.
 502                 */
 503                bytes = copy(substream, rec, bytes);
 504                rec->bytes2hw += bytes;
 505
 506#ifdef SND_PCM_INDIRECT2_STAT
 507                if (bytes < 64)
 508                        rec->byte_sizes[bytes]++;
 509                else
 510                        snd_printk(KERN_DEBUG
 511                                   "STAT: (capture) %d Bytes copied to "
 512                                   "hardware at once - too big to save!\n",
 513                                   bytes);
 514#endif
 515                /* increase sw_data by the number of actually copied bytes from
 516                 * HW
 517                 */
 518                rec->sw_data += bytes;
 519                if (rec->sw_data == rec->sw_buffer_size)
 520                        rec->sw_data = 0;
 521
 522                snd_pcm_indirect2_increase_min_periods(substream, rec, 0, 1,
 523                                                       bytes);
 524
 525                /* number of bytes in the intermediate buffer, which haven't
 526                 * been fetched by ALSA yet.
 527                 */
 528                rec->sw_ready += bytes;
 529        }
 530        return;
 531}
 532
 533/*
 534 * helper function for capture interrupt routine
 535 */
 536void
 537snd_pcm_indirect2_capture_interrupt(struct snd_pcm_substream *substream,
 538                                    struct snd_pcm_indirect2 *rec,
 539                                    snd_pcm_indirect2_copy_t copy,
 540                                    snd_pcm_indirect2_zero_t null)
 541{
 542#ifdef SND_PCM_INDIRECT2_STAT
 543        rec->irq_occured++;
 544#endif
 545        /* hardware recorded some bytes, so there is something to read from the
 546         * record fifo:
 547         */
 548        rec->hw_ready = 1;
 549
 550        /* don't call ack() now, instead call transfer() function directly
 551         * (normally called by ack() )
 552         */
 553        snd_pcm_indirect2_capture_transfer(substream, rec, copy, null);
 554
 555        if (rec->min_periods >= rec->min_multiple) {
 556
 557#ifdef SND_PCM_INDIRECT2_STAT
 558                if ((rec->min_periods / rec->min_multiple) > 7)
 559                        snd_printk(KERN_DEBUG
 560                                   "STAT: more than 7 (%d) mul_adds - "
 561                                   "too big to save!\n",
 562                                   (rec->min_periods / rec->min_multiple));
 563                else
 564                        rec->mul_adds[(rec->min_periods /
 565                                       rec->min_multiple)]++;
 566                rec->mul_elapsed_real += (rec->min_periods /
 567                                          rec->min_multiple);
 568                rec->mul_elapsed++;
 569#endif
 570                rec->min_periods = (rec->min_periods % rec->min_multiple);
 571                snd_pcm_period_elapsed(substream);
 572        }
 573}
 574
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