drivers/dma/dmatest.c

   1 /*
   2  * DMA Engine test module
   3  *
   4  * Copyright (C) 2007 Atmel Corporation
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  */
  10 #include <linux/delay.h>
  11 #include <linux/dmaengine.h>
  12 #include <linux/init.h>
  13 #include <linux/kthread.h>
  14 #include <linux/module.h>
  15 #include <linux/moduleparam.h>
  16 #include <linux/random.h>
  17 #include <linux/slab.h>
  18 #include <linux/wait.h>
  19
  20 static unsigned int test_buf_size = 16384;
  21 module_param(test_buf_size, uint, S_IRUGO);
  22 MODULE_PARM_DESC(test_buf_size, "Size of the memcpy test buffer");
  23
  24 static char test_channel[20];
  25 module_param_string(channel, test_channel, sizeof(test_channel), S_IRUGO);
  26 MODULE_PARM_DESC(channel, "Bus ID of the channel to test (default: any)");
  27
  28 static char test_device[20];
  29 module_param_string(device, test_device, sizeof(test_device), S_IRUGO);
  30 MODULE_PARM_DESC(device, "Bus ID of the DMA Engine to test (default: any)");
  31
  32 static unsigned int threads_per_chan = 1;
  33 module_param(threads_per_chan, uint, S_IRUGO);
  34 MODULE_PARM_DESC(threads_per_chan,
  35                 "Number of threads to start per channel (default: 1)");
  36
  37 static unsigned int max_channels;
  38 module_param(max_channels, uint, S_IRUGO);
  39 MODULE_PARM_DESC(max_channels,
  40                 "Maximum number of channels to use (default: all)");
  41
  42 static unsigned int iterations;
  43 module_param(iterations, uint, S_IRUGO);
  44 MODULE_PARM_DESC(iterations,
  45                 "Iterations before stopping test (default: infinite)");
  46
  47 static unsigned int xor_sources = 3;
  48 module_param(xor_sources, uint, S_IRUGO);
  49 MODULE_PARM_DESC(xor_sources,
  50                 "Number of xor source buffers (default: 3)");
  51
  52 static unsigned int pq_sources = 3;
  53 module_param(pq_sources, uint, S_IRUGO);
  54 MODULE_PARM_DESC(pq_sources,
  55                 "Number of p+q source buffers (default: 3)");
  56
  57 /*
  58  * Initialization patterns. All bytes in the source buffer has bit 7
  59  * set, all bytes in the destination buffer has bit 7 cleared.
  60  *
  61  * Bit 6 is set for all bytes which are to be copied by the DMA
  62  * engine. Bit 5 is set for all bytes which are to be overwritten by
  63  * the DMA engine.
  64  *
  65  * The remaining bits are the inverse of a counter which increments by
  66  * one for each byte address.
  67  */
  68 #define PATTERN_SRC             0x80
  69 #define PATTERN_DST             0x00
  70 #define PATTERN_COPY            0x40
  71 #define PATTERN_OVERWRITE       0x20
  72 #define PATTERN_COUNT_MASK      0x1f
  73
  74 struct dmatest_thread {
  75         struct list_head        node;
  76         struct task_struct      *task;
  77         struct dma_chan         *chan;
  78         u8                      **srcs;
  79         u8                      **dsts;
  80         enum dma_transaction_type type;
  81 };
  82
  83 struct dmatest_chan {
  84         struct list_head        node;
  85         struct dma_chan         *chan;
  86         struct list_head        threads;
  87 };
  88
  89 /*
  90  * These are protected by dma_list_mutex since they're only used by
  91  * the DMA filter function callback
  92  */
  93 static LIST_HEAD(dmatest_channels);
  94 static unsigned int nr_channels;
  95
  96 static bool dmatest_match_channel(struct dma_chan *chan)
  97 {
  98         if (test_channel[0] == '\0')
  99                 return true;
 100         return strcmp(dma_chan_name(chan), test_channel) == 0;
 101 }
 102
 103 static bool dmatest_match_device(struct dma_device *device)
 104 {
 105         if (test_device[0] == '\0')
 106                 return true;
 107         return strcmp(dev_name(device->dev), test_device) == 0;
 108 }
 109
 110 static unsigned long dmatest_random(void)
 111 {
 112         unsigned long buf;
 113
 114         get_random_bytes(&buf, sizeof(buf));
 115         return buf;
 116 }
 117
 118 static void dmatest_init_srcs(u8 **bufs, unsigned int start, unsigned int len)
 119 {
 120         unsigned int i;
 121         u8 *buf;
 122
 123         for (; (buf = *bufs); bufs++) {
 124                 for (i = 0; i < start; i++)
 125                         buf[i] = PATTERN_SRC | (~i & PATTERN_COUNT_MASK);
 126                 for ( ; i < start + len; i++)
 127                         buf[i] = PATTERN_SRC | PATTERN_COPY
 128                                 | (~i & PATTERN_COUNT_MASK);
 129                 for ( ; i < test_buf_size; i++)
 130                         buf[i] = PATTERN_SRC | (~i & PATTERN_COUNT_MASK);
 131                 buf++;
 132         }
 133 }
 134
 135 static void dmatest_init_dsts(u8 **bufs, unsigned int start, unsigned int len)
 136 {
 137         unsigned int i;
 138         u8 *buf;
 139
 140         for (; (buf = *bufs); bufs++) {
 141                 for (i = 0; i < start; i++)
 142                         buf[i] = PATTERN_DST | (~i & PATTERN_COUNT_MASK);
 143                 for ( ; i < start + len; i++)
 144                         buf[i] = PATTERN_DST | PATTERN_OVERWRITE
 145                                 | (~i & PATTERN_COUNT_MASK);
 146                 for ( ; i < test_buf_size; i++)
 147                         buf[i] = PATTERN_DST | (~i & PATTERN_COUNT_MASK);
 148         }
 149 }
 150
 151 static void dmatest_mismatch(u8 actual, u8 pattern, unsigned int index,
 152                 unsigned int counter, bool is_srcbuf)
 153 {
 154         u8              diff = actual ^ pattern;
 155         u8              expected = pattern | (~counter & PATTERN_COUNT_MASK);
 156         const char      *thread_name = current->comm;
 157
 158         if (is_srcbuf)
 159                 pr_warning("%s: srcbuf[0x%x] overwritten!"
 160                                 " Expected %02x, got %02x\n",
 161                                 thread_name, index, expected, actual);
 162         else if ((pattern & PATTERN_COPY)
 163                         && (diff & (PATTERN_COPY | PATTERN_OVERWRITE)))
 164                 pr_warning("%s: dstbuf[0x%x] not copied!"
 165                                 " Expected %02x, got %02x\n",
 166                                 thread_name, index, expected, actual);
 167         else if (diff & PATTERN_SRC)
 168                 pr_warning("%s: dstbuf[0x%x] was copied!"
 169                                 " Expected %02x, got %02x\n",
 170                                 thread_name, index, expected, actual);
 171         else
 172                 pr_warning("%s: dstbuf[0x%x] mismatch!"
 173                                 " Expected %02x, got %02x\n",
 174                                 thread_name, index, expected, actual);
 175 }
 176
 177 static unsigned int dmatest_verify(u8 **bufs, unsigned int start,
 178                 unsigned int end, unsigned int counter, u8 pattern,
 179                 bool is_srcbuf)
 180 {
 181         unsigned int i;
 182         unsigned int error_count = 0;
 183         u8 actual;
 184         u8 expected;
 185         u8 *buf;
 186         unsigned int counter_orig = counter;
 187
 188         for (; (buf = *bufs); bufs++) {
 189                 counter = counter_orig;
 190                 for (i = start; i < end; i++) {
 191                         actual = buf[i];
 192                         expected = pattern | (~counter & PATTERN_COUNT_MASK);
 193                         if (actual != expected) {
 194                                 if (error_count < 32)
 195                                         dmatest_mismatch(actual, pattern, i,
 196                                                          counter, is_srcbuf);
 197                                 error_count++;
 198                         }
 199                         counter++;
 200                 }
 201         }
 202
 203         if (error_count > 32)
 204                 pr_warning("%s: %u errors suppressed\n",
 205                         current->comm, error_count - 32);
 206
 207         return error_count;
 208 }
 209
 210 static void dmatest_callback(void *completion)
 211 {
 212         complete(completion);
 213 }
 214
 215 /*
 216  * This function repeatedly tests DMA transfers of various lengths and
 217  * offsets for a given operation type until it is told to exit by
 218  * kthread_stop(). There may be multiple threads running this function
 219  * in parallel for a single channel, and there may be multiple channels
 220  * being tested in parallel.
 221  *
 222  * Before each test, the source and destination buffer is initialized
 223  * with a known pattern. This pattern is different depending on
 224  * whether it's in an area which is supposed to be copied or
 225  * overwritten, and different in the source and destination buffers.
 226  * So if the DMA engine doesn't copy exactly what we tell it to copy,
 227  * we'll notice.
 228  */
 229 static int dmatest_func(void *data)
 230 {
 231         struct dmatest_thread   *thread = data;
 232         struct dma_chan         *chan;
 233         const char              *thread_name;
 234         unsigned int            src_off, dst_off, len;
 235         unsigned int            error_count;
 236         unsigned int            failed_tests = 0;
 237         unsigned int            total_tests = 0;
 238         dma_cookie_t            cookie;
 239         enum dma_status         status;
 240         enum dma_ctrl_flags     flags;
 241         u8                      pq_coefs[pq_sources + 1];
 242         int                     ret;
 243         int                     src_cnt;
 244         int                     dst_cnt;
 245         int                     i;
 246
 247         thread_name = current->comm;
 248
 249         ret = -ENOMEM;
 250
 251         smp_rmb();
 252         chan = thread->chan;
 253         if (thread->type == DMA_MEMCPY)
 254                 src_cnt = dst_cnt = 1;
 255         else if (thread->type == DMA_XOR) {
 256                 src_cnt = xor_sources | 1; /* force odd to ensure dst = src */
 257                 dst_cnt = 1;
 258         } else if (thread->type == DMA_PQ) {
 259                 src_cnt = pq_sources | 1; /* force odd to ensure dst = src */
 260                 dst_cnt = 2;
 261                 for (i = 0; i < src_cnt; i++)
 262                         pq_coefs[i] = 1;
 263         } else
 264                 goto err_srcs;
 265
 266         thread->srcs = kcalloc(src_cnt+1, sizeof(u8 *), GFP_KERNEL);
 267         if (!thread->srcs)
 268                 goto err_srcs;
 269         for (i = 0; i < src_cnt; i++) {
 270                 thread->srcs[i] = kmalloc(test_buf_size, GFP_KERNEL);
 271                 if (!thread->srcs[i])
 272                         goto err_srcbuf;
 273         }
 274         thread->srcs[i] = NULL;
 275
 276         thread->dsts = kcalloc(dst_cnt+1, sizeof(u8 *), GFP_KERNEL);
 277         if (!thread->dsts)
 278                 goto err_dsts;
 279         for (i = 0; i < dst_cnt; i++) {
 280                 thread->dsts[i] = kmalloc(test_buf_size, GFP_KERNEL);
 281                 if (!thread->dsts[i])
 282                         goto err_dstbuf;
 283         }
 284         thread->dsts[i] = NULL;
 285
 286         set_user_nice(current, 10);
 287
 288         flags = DMA_CTRL_ACK | DMA_COMPL_SKIP_DEST_UNMAP | DMA_PREP_INTERRUPT;
 289
 290         while (!kthread_should_stop()
 291                && !(iterations && total_tests >= iterations)) {
 292                 struct dma_device *dev = chan->device;
 293                 struct dma_async_tx_descriptor *tx = NULL;
 294                 dma_addr_t dma_srcs[src_cnt];
 295                 dma_addr_t dma_dsts[dst_cnt];
 296                 struct completion cmp;
 297                 unsigned long tmo = msecs_to_jiffies(3000);
 298                 u8 align = 0;
 299
 300                 total_tests++;
 301
 302                 /* honor alignment restrictions */
 303                 if (thread->type == DMA_MEMCPY)
 304                         align = dev->copy_align;
 305                 else if (thread->type == DMA_XOR)
 306                         align = dev->xor_align;
 307                 else if (thread->type == DMA_PQ)
 308                         align = dev->pq_align;
 309
 310                 if (1 << align > test_buf_size) {
 311                         pr_err("%u-byte buffer too small for %d-byte alignment\n",
 312                                test_buf_size, 1 << align);
 313                         break;
 314                 }
 315
 316                 len = dmatest_random() % test_buf_size + 1;
 317                 len = (len >> align) << align;
 318                 if (!len)
 319                         len = 1 << align;
 320                 src_off = dmatest_random() % (test_buf_size - len + 1);
 321                 dst_off = dmatest_random() % (test_buf_size - len + 1);
 322
 323                 src_off = (src_off >> align) << align;
 324                 dst_off = (dst_off >> align) << align;
 325
 326                 dmatest_init_srcs(thread->srcs, src_off, len);
 327                 dmatest_init_dsts(thread->dsts, dst_off, len);
 328
 329                 for (i = 0; i < src_cnt; i++) {
 330                         u8 *buf = thread->srcs[i] + src_off;
 331
 332                         dma_srcs[i] = dma_map_single(dev->dev, buf, len,
 333                                                      DMA_TO_DEVICE);
 334                 }
 335                 /* map with DMA_BIDIRECTIONAL to force writeback/invalidate */
 336                 for (i = 0; i < dst_cnt; i++) {
 337                         dma_dsts[i] = dma_map_single(dev->dev, thread->dsts[i],
 338                                                      test_buf_size,
 339                                                      DMA_BIDIRECTIONAL);
 340                 }
 341
 342
 343                 if (thread->type == DMA_MEMCPY)
 344                         tx = dev->device_prep_dma_memcpy(chan,
 345                                                          dma_dsts[0] + dst_off,
 346                                                          dma_srcs[0], len,
 347                                                          flags);
 348                 else if (thread->type == DMA_XOR)
 349                         tx = dev->device_prep_dma_xor(chan,
 350                                                       dma_dsts[0] + dst_off,
 351                                                       dma_srcs, src_cnt,
 352                                                       len, flags);
 353                 else if (thread->type == DMA_PQ) {
 354                         dma_addr_t dma_pq[dst_cnt];
 355
 356                         for (i = 0; i < dst_cnt; i++)
 357                                 dma_pq[i] = dma_dsts[i] + dst_off;
 358                         tx = dev->device_prep_dma_pq(chan, dma_pq, dma_srcs,
 359                                                      src_cnt, pq_coefs,
 360                                                      len, flags);
 361                 }
 362
 363                 if (!tx) {
 364                         for (i = 0; i < src_cnt; i++)
 365                                 dma_unmap_single(dev->dev, dma_srcs[i], len,
 366                                                  DMA_TO_DEVICE);
 367                         for (i = 0; i < dst_cnt; i++)
 368                                 dma_unmap_single(dev->dev, dma_dsts[i],
 369                                                  test_buf_size,
 370                                                  DMA_BIDIRECTIONAL);
 371                         pr_warning("%s: #%u: prep error with src_off=0x%x "
 372                                         "dst_off=0x%x len=0x%x\n",
 373                                         thread_name, total_tests - 1,
 374                                         src_off, dst_off, len);
 375                         msleep(100);
 376                         failed_tests++;
 377                         continue;
 378                 }
 379
 380                 init_completion(&cmp);
 381                 tx->callback = dmatest_callback;
 382                 tx->callback_param = &cmp;
 383                 cookie = tx->tx_submit(tx);
 384
 385                 if (dma_submit_error(cookie)) {
 386                         pr_warning("%s: #%u: submit error %d with src_off=0x%x "
 387                                         "dst_off=0x%x len=0x%x\n",
 388                                         thread_name, total_tests - 1, cookie,
 389                                         src_off, dst_off, len);
 390                         msleep(100);
 391                         failed_tests++;
 392                         continue;
 393                 }
 394                 dma_async_issue_pending(chan);
 395
 396                 tmo = wait_for_completion_timeout(&cmp, tmo);
 397                 status = dma_async_is_tx_complete(chan, cookie, NULL, NULL);
 398
 399                 if (tmo == 0) {
 400                         pr_warning("%s: #%u: test timed out\n",
 401                                    thread_name, total_tests - 1);
 402                         failed_tests++;
 403                         continue;
 404                 } else if (status != DMA_SUCCESS) {
 405                         pr_warning("%s: #%u: got completion callback,"
 406                                    " but status is \'%s\'\n",
 407                                    thread_name, total_tests - 1,
 408                                    status == DMA_ERROR ? "error" : "in progress");
 409                         failed_tests++;
 410                         continue;
 411                 }
 412
 413                 /* Unmap by myself (see DMA_COMPL_SKIP_DEST_UNMAP above) */
 414                 for (i = 0; i < dst_cnt; i++)
 415                         dma_unmap_single(dev->dev, dma_dsts[i], test_buf_size,
 416                                          DMA_BIDIRECTIONAL);
 417
 418                 error_count = 0;
 419
 420                 pr_debug("%s: verifying source buffer...\n", thread_name);
 421                 error_count += dmatest_verify(thread->srcs, 0, src_off,
 422                                 0, PATTERN_SRC, true);
 423                 error_count += dmatest_verify(thread->srcs, src_off,
 424                                 src_off + len, src_off,
 425                                 PATTERN_SRC | PATTERN_COPY, true);
 426                 error_count += dmatest_verify(thread->srcs, src_off + len,
 427                                 test_buf_size, src_off + len,
 428                                 PATTERN_SRC, true);
 429
 430                 pr_debug("%s: verifying dest buffer...\n",
 431                                 thread->task->comm);
 432                 error_count += dmatest_verify(thread->dsts, 0, dst_off,
 433                                 0, PATTERN_DST, false);
 434                 error_count += dmatest_verify(thread->dsts, dst_off,
 435                                 dst_off + len, src_off,
 436                                 PATTERN_SRC | PATTERN_COPY, false);
 437                 error_count += dmatest_verify(thread->dsts, dst_off + len,
 438                                 test_buf_size, dst_off + len,
 439                                 PATTERN_DST, false);
 440
 441                 if (error_count) {
 442                         pr_warning("%s: #%u: %u errors with "
 443                                 "src_off=0x%x dst_off=0x%x len=0x%x\n",
 444                                 thread_name, total_tests - 1, error_count,
 445                                 src_off, dst_off, len);
 446                         failed_tests++;
 447                 } else {
 448                         pr_debug("%s: #%u: No errors with "
 449                                 "src_off=0x%x dst_off=0x%x len=0x%x\n",
 450                                 thread_name, total_tests - 1,
 451                                 src_off, dst_off, len);
 452                 }
 453         }
 454
 455         ret = 0;
 456         for (i = 0; thread->dsts[i]; i++)
 457                 kfree(thread->dsts[i]);
 458 err_dstbuf:
 459         kfree(thread->dsts);
 460 err_dsts:
 461         for (i = 0; thread->srcs[i]; i++)
 462                 kfree(thread->srcs[i]);
 463 err_srcbuf:
 464         kfree(thread->srcs);
 465 err_srcs:
 466         pr_notice("%s: terminating after %u tests, %u failures (status %d)\n",
 467                         thread_name, total_tests, failed_tests, ret);
 468
 469         if (iterations > 0)
 470                 while (!kthread_should_stop()) {
 471                         DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wait_dmatest_exit);
 472                         interruptible_sleep_on(&wait_dmatest_exit);
 473                 }
 474
 475         return ret;
 476 }
 477
 478 static void dmatest_cleanup_channel(struct dmatest_chan *dtc)
 479 {
 480         struct dmatest_thread   *thread;
 481         struct dmatest_thread   *_thread;
 482         int                     ret;
 483
 484         list_for_each_entry_safe(thread, _thread, &dtc->threads, node) {
 485                 ret = kthread_stop(thread->task);
 486                 pr_debug("dmatest: thread %s exited with status %d\n",
 487                                 thread->task->comm, ret);
 488                 list_del(&thread->node);
 489                 kfree(thread);
 490         }
 491         kfree(dtc);
 492 }
 493
 494 static int dmatest_add_threads(struct dmatest_chan *dtc, enum dma_transaction_type type)
 495 {
 496         struct dmatest_thread *thread;
 497         struct dma_chan *chan = dtc->chan;
 498         char *op;
 499         unsigned int i;
 500
 501         if (type == DMA_MEMCPY)
 502                 op = "copy";
 503         else if (type == DMA_XOR)
 504                 op = "xor";
 505         else if (type == DMA_PQ)
 506                 op = "pq";
 507         else
 508                 return -EINVAL;
 509
 510         for (i = 0; i < threads_per_chan; i++) {
 511                 thread = kzalloc(sizeof(struct dmatest_thread), GFP_KERNEL);
 512                 if (!thread) {
 513                         pr_warning("dmatest: No memory for %s-%s%u\n",
 514                                    dma_chan_name(chan), op, i);
 515
 516                         break;
 517                 }
 518                 thread->chan = dtc->chan;
 519                 thread->type = type;
 520                 smp_wmb();
 521                 thread->task = kthread_run(dmatest_func, thread, "%s-%s%u",
 522                                 dma_chan_name(chan), op, i);
 523                 if (IS_ERR(thread->task)) {
 524                         pr_warning("dmatest: Failed to run thread %s-%s%u\n",
 525                                         dma_chan_name(chan), op, i);
 526                         kfree(thread);
 527                         break;
 528                 }
 529
 530                 /* srcbuf and dstbuf are allocated by the thread itself */
 531
 532                 list_add_tail(&thread->node, &dtc->threads);
 533         }
 534
 535         return i;
 536 }
 537
 538 static int dmatest_add_channel(struct dma_chan *chan)
 539 {
 540         struct dmatest_chan     *dtc;
 541         struct dma_device       *dma_dev = chan->device;
 542         unsigned int            thread_count = 0;
 543         int cnt;
 544
 545         dtc = kmalloc(sizeof(struct dmatest_chan), GFP_KERNEL);
 546         if (!dtc) {
 547                 pr_warning("dmatest: No memory for %s\n", dma_chan_name(chan));
 548                 return -ENOMEM;
 549         }
 550
 551         dtc->chan = chan;
 552         INIT_LIST_HEAD(&dtc->threads);
 553
 554         if (dma_has_cap(DMA_MEMCPY, dma_dev->cap_mask)) {
 555                 cnt = dmatest_add_threads(dtc, DMA_MEMCPY);
 556                 thread_count += cnt > 0 ? cnt : 0;
 557         }
 558         if (dma_has_cap(DMA_XOR, dma_dev->cap_mask)) {
 559                 cnt = dmatest_add_threads(dtc, DMA_XOR);
 560                 thread_count += cnt > 0 ? cnt : 0;
 561         }
 562         if (dma_has_cap(DMA_PQ, dma_dev->cap_mask)) {
 563                 cnt = dmatest_add_threads(dtc, DMA_PQ);
 564                 thread_count += cnt > 0 ?: 0;
 565         }
 566
 567         pr_info("dmatest: Started %u threads using %s\n",
 568                 thread_count, dma_chan_name(chan));
 569
 570         list_add_tail(&dtc->node, &dmatest_channels);
 571         nr_channels++;
 572
 573         return 0;
 574 }
 575
 576 static bool filter(struct dma_chan *chan, void *param)
 577 {
 578         if (!dmatest_match_channel(chan) || !dmatest_match_device(chan->device))
 579                 return false;
 580         else
 581                 return true;
 582 }
 583
 584 static int __init dmatest_init(void)
 585 {
 586         dma_cap_mask_t mask;
 587         struct dma_chan *chan;
 588         int err = 0;
 589
 590         dma_cap_zero(mask);
 591         dma_cap_set(DMA_MEMCPY, mask);
 592         for (;;) {
 593                 chan = dma_request_channel(mask, filter, NULL);
 594                 if (chan) {
 595                         err = dmatest_add_channel(chan);
 596                         if (err) {
 597                                 dma_release_channel(chan);
 598                                 break; /* add_channel failed, punt */
 599                         }
 600                 } else
 601                         break; /* no more channels available */
 602                 if (max_channels && nr_channels >= max_channels)
 603                         break; /* we have all we need */
 604         }
 605
 606         return err;
 607 }
 608 /* when compiled-in wait for drivers to load first */
 609 late_initcall(dmatest_init);
 610
 611 static void __exit dmatest_exit(void)
 612 {
 613         struct dmatest_chan *dtc, *_dtc;
 614         struct dma_chan *chan;
 615
 616         list_for_each_entry_safe(dtc, _dtc, &dmatest_channels, node) {
 617                 list_del(&dtc->node);
 618                 chan = dtc->chan;
 619                 dmatest_cleanup_channel(dtc);
 620                 pr_debug("dmatest: dropped channel %s\n",
 621                          dma_chan_name(chan));
 622                 dma_release_channel(chan);
 623         }
 624 }
 625 module_exit(dmatest_exit);
 626
 627 MODULE_AUTHOR("Haavard Skinnemoen <hskinnemoen@atmel.com>");
 628 MODULE_LICENSE("GPL v2");