2 * linux/drivers/spi/spi-loopback-test.c
4 * (c) Martin Sperl <kernel@martin.sperl.org>
6 * Loopback test driver to test several typical spi_message conditions
7 * that a spi_master driver may encounter
8 * this can also get used for regression testing
10 * This program is free software; you can redistribute it and/or modify
11 * it under the terms of the GNU General Public License as published by
12 * the Free Software Foundation; either version 2 of the License, or
13 * (at your option) any later version.
15 * This program is distributed in the hope that it will be useful,
16 * but WITHOUT ANY WARRANTY; without even the implied warranty of
17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 * GNU General Public License for more details.
21 #include <linux/delay.h>
22 #include <linux/kernel.h>
23 #include <linux/ktime.h>
24 #include <linux/list.h>
25 #include <linux/list_sort.h>
26 #include <linux/module.h>
27 #include <linux/of_device.h>
28 #include <linux/printk.h>
29 #include <linux/spi/spi.h>
33 /* flag to only simulate transfers */
35 module_param(simulate_only, int, 0);
36 MODULE_PARM_DESC(simulate_only, "if not 0 do not execute the spi message");
38 /* dump spi messages */
40 module_param(dump_messages, int, 0);
41 MODULE_PARM_DESC(dump_messages,
42 "=1 dump the basic spi_message_structure, " \
43 "=2 dump the spi_message_structure including data, " \
44 "=3 dump the spi_message structure before and after execution");
45 /* the device is jumpered for loopback - enabling some rx_buf tests */
47 module_param(loopback, int, 0);
48 MODULE_PARM_DESC(loopback,
49 "if set enable loopback mode, where the rx_buf " \
50 "is checked to match tx_buf after the spi_message " \
53 /* run only a specific test */
54 int run_only_test = -1;
55 module_param(run_only_test, int, 0);
56 MODULE_PARM_DESC(run_only_test,
57 "only run the test with this number (0-based !)");
59 /* the actual tests to execute */
60 static struct spi_test spi_tests[] = {
62 .description = "tx/rx-transfer - start of page",
63 .fill_option = FILL_COUNT_8,
64 .iterate_len = { ITERATE_MAX_LEN },
65 .iterate_tx_align = ITERATE_ALIGN,
66 .iterate_rx_align = ITERATE_ALIGN,
76 .description = "tx/rx-transfer - crossing PAGE_SIZE",
77 .fill_option = FILL_COUNT_8,
78 .iterate_len = { ITERATE_MAX_LEN },
79 .iterate_tx_align = ITERATE_ALIGN,
80 .iterate_rx_align = ITERATE_ALIGN,
84 .tx_buf = TX(PAGE_SIZE - 4),
85 .rx_buf = RX(PAGE_SIZE - 4),
90 .description = "tx-transfer - only",
91 .fill_option = FILL_COUNT_8,
92 .iterate_len = { ITERATE_MAX_LEN },
93 .iterate_tx_align = ITERATE_ALIGN,
102 .description = "rx-transfer - only",
103 .fill_option = FILL_COUNT_8,
104 .iterate_len = { ITERATE_MAX_LEN },
105 .iterate_rx_align = ITERATE_ALIGN,
114 .description = "two tx-transfers - alter both",
115 .fill_option = FILL_COUNT_8,
116 .iterate_len = { ITERATE_LEN },
117 .iterate_tx_align = ITERATE_ALIGN,
118 .iterate_transfer_mask = BIT(0) | BIT(1),
125 /* this is why we cant use ITERATE_MAX_LEN */
126 .tx_buf = TX(SPI_TEST_MAX_SIZE_HALF),
131 .description = "two tx-transfers - alter first",
132 .fill_option = FILL_COUNT_8,
133 .iterate_len = { ITERATE_MAX_LEN },
134 .iterate_tx_align = ITERATE_ALIGN,
135 .iterate_transfer_mask = BIT(0),
148 .description = "two tx-transfers - alter second",
149 .fill_option = FILL_COUNT_8,
150 .iterate_len = { ITERATE_MAX_LEN },
151 .iterate_tx_align = ITERATE_ALIGN,
152 .iterate_transfer_mask = BIT(1),
165 .description = "two transfers tx then rx - alter both",
166 .fill_option = FILL_COUNT_8,
167 .iterate_len = { ITERATE_MAX_LEN },
168 .iterate_tx_align = ITERATE_ALIGN,
169 .iterate_transfer_mask = BIT(0) | BIT(1),
181 .description = "two transfers tx then rx - alter tx",
182 .fill_option = FILL_COUNT_8,
183 .iterate_len = { ITERATE_MAX_LEN },
184 .iterate_tx_align = ITERATE_ALIGN,
185 .iterate_transfer_mask = BIT(0),
198 .description = "two transfers tx then rx - alter rx",
199 .fill_option = FILL_COUNT_8,
200 .iterate_len = { ITERATE_MAX_LEN },
201 .iterate_tx_align = ITERATE_ALIGN,
202 .iterate_transfer_mask = BIT(1),
215 .description = "two tx+rx transfers - alter both",
216 .fill_option = FILL_COUNT_8,
217 .iterate_len = { ITERATE_LEN },
218 .iterate_tx_align = ITERATE_ALIGN,
219 .iterate_transfer_mask = BIT(0) | BIT(1),
227 /* making sure we align without overwrite
228 * the reason we can not use ITERATE_MAX_LEN
230 .tx_buf = TX(SPI_TEST_MAX_SIZE_HALF),
231 .rx_buf = RX(SPI_TEST_MAX_SIZE_HALF),
236 .description = "two tx+rx transfers - alter first",
237 .fill_option = FILL_COUNT_8,
238 .iterate_len = { ITERATE_MAX_LEN },
239 .iterate_tx_align = ITERATE_ALIGN,
240 .iterate_transfer_mask = BIT(0),
244 /* making sure we align without overwrite */
250 /* making sure we align without overwrite */
257 .description = "two tx+rx transfers - alter second",
258 .fill_option = FILL_COUNT_8,
259 .iterate_len = { ITERATE_MAX_LEN },
260 .iterate_tx_align = ITERATE_ALIGN,
261 .iterate_transfer_mask = BIT(1),
270 /* making sure we align without overwrite */
277 .description = "two tx+rx transfers - delay after transfer",
278 .fill_option = FILL_COUNT_8,
279 .iterate_len = { ITERATE_MAX_LEN },
280 .iterate_transfer_mask = BIT(0) | BIT(1),
296 { /* end of tests sequence */ }
299 static int spi_loopback_test_probe(struct spi_device *spi)
303 dev_info(&spi->dev, "Executing spi-loopback-tests\n");
305 ret = spi_test_run_tests(spi, spi_tests);
307 dev_info(&spi->dev, "Finished spi-loopback-tests with return: %i\n",
313 /* non const match table to permit to change via a module parameter */
314 static struct of_device_id spi_loopback_test_of_match[] = {
315 { .compatible = "linux,spi-loopback-test", },
319 /* allow to override the compatible string via a module_parameter */
320 module_param_string(compatible, spi_loopback_test_of_match[0].compatible,
321 sizeof(spi_loopback_test_of_match[0].compatible),
324 MODULE_DEVICE_TABLE(of, spi_loopback_test_of_match);
326 static struct spi_driver spi_loopback_test_driver = {
328 .name = "spi-loopback-test",
329 .owner = THIS_MODULE,
330 .of_match_table = spi_loopback_test_of_match,
332 .probe = spi_loopback_test_probe,
335 module_spi_driver(spi_loopback_test_driver);
337 MODULE_AUTHOR("Martin Sperl <kernel@martin.sperl.org>");
338 MODULE_DESCRIPTION("test spi_driver to check core functionality");
339 MODULE_LICENSE("GPL");
341 /*-------------------------------------------------------------------------*/
343 /* spi_test implementation */
345 #define RANGE_CHECK(ptr, plen, start, slen) \
346 ((ptr >= start) && (ptr + plen <= start + slen))
348 /* we allocate one page more, to allow for offsets */
349 #define SPI_TEST_MAX_SIZE_PLUS (SPI_TEST_MAX_SIZE + PAGE_SIZE)
351 static void spi_test_print_hex_dump(char *pre, const void *ptr, size_t len)
353 /* limit the hex_dump */
355 print_hex_dump(KERN_INFO, pre,
356 DUMP_PREFIX_OFFSET, 16, 1,
361 print_hex_dump(KERN_INFO, pre,
362 DUMP_PREFIX_OFFSET, 16, 1,
365 pr_info("%s truncated - continuing at offset %04zx\n",
367 print_hex_dump(KERN_INFO, pre,
368 DUMP_PREFIX_OFFSET, 16, 1,
369 ptr + (len - 512), 512, 0);
372 static void spi_test_dump_message(struct spi_device *spi,
373 struct spi_message *msg,
376 struct spi_transfer *xfer;
380 dev_info(&spi->dev, " spi_msg@%pK\n", msg);
382 dev_info(&spi->dev, " status: %i\n",
384 dev_info(&spi->dev, " frame_length: %i\n",
386 dev_info(&spi->dev, " actual_length: %i\n",
389 list_for_each_entry(xfer, &msg->transfers, transfer_list) {
390 dev_info(&spi->dev, " spi_transfer@%pK\n", xfer);
391 dev_info(&spi->dev, " len: %i\n", xfer->len);
392 dev_info(&spi->dev, " tx_buf: %pK\n", xfer->tx_buf);
393 if (dump_data && xfer->tx_buf)
394 spi_test_print_hex_dump(" TX: ",
398 dev_info(&spi->dev, " rx_buf: %pK\n", xfer->rx_buf);
399 if (dump_data && xfer->rx_buf)
400 spi_test_print_hex_dump(" RX: ",
403 /* check for unwritten test pattern on rx_buf */
405 for (i = 0 ; i < xfer->len ; i++) {
406 b = ((u8 *)xfer->rx_buf)[xfer->len - 1 - i];
407 if (b != SPI_TEST_PATTERN_UNWRITTEN)
412 " rx_buf filled with %02x starts at offset: %i\n",
413 SPI_TEST_PATTERN_UNWRITTEN,
420 struct list_head list;
425 static int rx_ranges_cmp(void *priv, struct list_head *a, struct list_head *b)
427 struct rx_ranges *rx_a = list_entry(a, struct rx_ranges, list);
428 struct rx_ranges *rx_b = list_entry(b, struct rx_ranges, list);
430 if (rx_a->start > rx_b->start)
432 if (rx_a->start < rx_b->start)
437 static int spi_check_rx_ranges(struct spi_device *spi,
438 struct spi_message *msg,
441 struct spi_transfer *xfer;
442 struct rx_ranges ranges[SPI_TEST_MAX_TRANSFERS], *r;
444 LIST_HEAD(ranges_list);
448 /* loop over all transfers to fill in the rx_ranges */
449 list_for_each_entry(xfer, &msg->transfers, transfer_list) {
450 /* if there is no rx, then no check is needed */
453 /* fill in the rx_range */
454 if (RANGE_CHECK(xfer->rx_buf, xfer->len,
455 rx, SPI_TEST_MAX_SIZE_PLUS)) {
456 ranges[i].start = xfer->rx_buf;
457 ranges[i].end = xfer->rx_buf + xfer->len;
458 list_add(&ranges[i].list, &ranges_list);
463 /* if no ranges, then we can return and avoid the checks...*/
468 list_sort(NULL, &ranges_list, rx_ranges_cmp);
470 /* and iterate over all the rx addresses */
471 for (addr = rx; addr < (u8 *)rx + SPI_TEST_MAX_SIZE_PLUS; addr++) {
472 /* if we are the DO not write pattern,
473 * then continue with the loop...
475 if (*addr == SPI_TEST_PATTERN_DO_NOT_WRITE)
478 /* check if we are inside a range */
479 list_for_each_entry(r, &ranges_list, list) {
480 /* if so then set to end... */
481 if ((addr >= r->start) && (addr < r->end))
484 /* second test after a (hopefull) translation */
485 if (*addr == SPI_TEST_PATTERN_DO_NOT_WRITE)
488 /* if still not found then something has modified too much */
489 /* we could list the "closest" transfer here... */
491 "loopback strangeness - rx changed outside of allowed range at: %pK\n",
493 /* do not return, only set ret,
494 * so that we list all addresses
502 static int spi_test_check_elapsed_time(struct spi_device *spi,
503 struct spi_test *test)
506 unsigned long long estimated_time = 0;
507 unsigned long long delay_usecs = 0;
509 for (i = 0; i < test->transfer_count; i++) {
510 struct spi_transfer *xfer = test->transfers + i;
511 unsigned long long nbits = (unsigned long long)BITS_PER_BYTE *
514 delay_usecs += xfer->delay_usecs;
517 estimated_time += div_u64(nbits * NSEC_PER_SEC, xfer->speed_hz);
520 estimated_time += delay_usecs * NSEC_PER_USEC;
521 if (test->elapsed_time < estimated_time) {
523 "elapsed time %lld ns is shorter than minimam estimated time %lld ns\n",
524 test->elapsed_time, estimated_time);
532 static int spi_test_check_loopback_result(struct spi_device *spi,
533 struct spi_message *msg,
536 struct spi_transfer *xfer;
541 /* checks rx_buffer pattern are valid with loopback or without */
542 ret = spi_check_rx_ranges(spi, msg, rx);
546 /* if we run without loopback, then return now */
550 /* if applicable to transfer check that rx_buf is equal to tx_buf */
551 list_for_each_entry(xfer, &msg->transfers, transfer_list) {
552 /* if there is no rx, then no check is needed */
553 if (!xfer->len || !xfer->rx_buf)
555 /* so depending on tx_buf we need to handle things */
557 for (i = 0; i < xfer->len; i++) {
558 txb = ((u8 *)xfer->tx_buf)[i];
559 rxb = ((u8 *)xfer->rx_buf)[i];
564 /* first byte received */
565 txb = ((u8 *)xfer->rx_buf)[0];
566 /* first byte may be 0 or xff */
567 if (!((txb == 0) || (txb == 0xff))) {
569 "loopback strangeness - we expect 0x00 or 0xff, but not 0x%02x\n",
573 /* check that all bytes are identical */
574 for (i = 1; i < xfer->len; i++) {
575 rxb = ((u8 *)xfer->rx_buf)[i];
586 "loopback strangeness - transfer mismatch on byte %04zx - expected 0x%02x, but got 0x%02x\n",
592 static int spi_test_translate(struct spi_device *spi,
593 void **ptr, size_t len,
602 /* in the MAX_SIZE_HALF case modify the pointer */
603 if (((size_t)*ptr) & SPI_TEST_MAX_SIZE_HALF)
604 /* move the pointer to the correct range */
605 *ptr += (SPI_TEST_MAX_SIZE_PLUS / 2) -
606 SPI_TEST_MAX_SIZE_HALF;
609 * - we check against MAX_SIZE_PLUS to allow for automated alignment
611 if (RANGE_CHECK(*ptr, len, RX(0), SPI_TEST_MAX_SIZE_PLUS)) {
619 if (RANGE_CHECK(*ptr, len, TX(0), SPI_TEST_MAX_SIZE_PLUS)) {
627 "PointerRange [%pK:%pK[ not in range [%pK:%pK[ or [%pK:%pK[\n",
629 RX(0), RX(SPI_TEST_MAX_SIZE),
630 TX(0), TX(SPI_TEST_MAX_SIZE));
635 static int spi_test_fill_pattern(struct spi_device *spi,
636 struct spi_test *test)
638 struct spi_transfer *xfers = test->transfers;
644 #define GET_VALUE_BYTE(value, index, bytes) \
645 (value >> (8 * (bytes - 1 - count % bytes)))
647 #define GET_VALUE_BYTE(value, index, bytes) \
648 (value >> (8 * (count % bytes)))
651 /* fill all transfers with the pattern requested */
652 for (i = 0; i < test->transfer_count; i++) {
653 /* fill rx_buf with SPI_TEST_PATTERN_UNWRITTEN */
655 memset(xfers[i].rx_buf, SPI_TEST_PATTERN_UNWRITTEN,
657 /* if tx_buf is NULL then skip */
658 tx_buf = (u8 *)xfers[i].tx_buf;
661 /* modify all the transfers */
662 for (j = 0; j < xfers[i].len; j++, tx_buf++, count++) {
664 switch (test->fill_option) {
666 *tx_buf = test->fill_pattern;
669 *tx_buf = GET_VALUE_BYTE(test->fill_pattern,
673 *tx_buf = GET_VALUE_BYTE(test->fill_pattern,
677 *tx_buf = GET_VALUE_BYTE(test->fill_pattern,
684 *tx_buf = GET_VALUE_BYTE(count, count, 2);
687 *tx_buf = GET_VALUE_BYTE(count, count, 3);
690 *tx_buf = GET_VALUE_BYTE(count, count, 4);
692 case FILL_TRANSFER_BYTE_8:
695 case FILL_TRANSFER_BYTE_16:
696 *tx_buf = GET_VALUE_BYTE(j, j, 2);
698 case FILL_TRANSFER_BYTE_24:
699 *tx_buf = GET_VALUE_BYTE(j, j, 3);
701 case FILL_TRANSFER_BYTE_32:
702 *tx_buf = GET_VALUE_BYTE(j, j, 4);
704 case FILL_TRANSFER_NUM:
709 "unsupported fill_option: %i\n",
719 static int _spi_test_run_iter(struct spi_device *spi,
720 struct spi_test *test,
723 struct spi_message *msg = &test->msg;
724 struct spi_transfer *x;
727 /* initialize message - zero-filled via static initialization */
728 spi_message_init_no_memset(msg);
730 /* fill rx with the DO_NOT_WRITE pattern */
731 memset(rx, SPI_TEST_PATTERN_DO_NOT_WRITE, SPI_TEST_MAX_SIZE_PLUS);
733 /* add the individual transfers */
734 for (i = 0; i < test->transfer_count; i++) {
735 x = &test->transfers[i];
737 /* patch the values of tx_buf */
738 ret = spi_test_translate(spi, (void **)&x->tx_buf, x->len,
743 /* patch the values of rx_buf */
744 ret = spi_test_translate(spi, &x->rx_buf, x->len,
749 /* and add it to the list */
750 spi_message_add_tail(x, msg);
753 /* fill in the transfer buffers with pattern */
754 ret = spi_test_fill_pattern(spi, test);
759 if (test->execute_msg)
760 ret = test->execute_msg(spi, test, tx, rx);
762 ret = spi_test_execute_msg(spi, test, tx, rx);
765 if (ret == test->expected_return)
769 "test failed - test returned %i, but we expect %i\n",
770 ret, test->expected_return);
775 /* if it is 0, as we expected something else,
776 * then return something special
781 static int spi_test_run_iter(struct spi_device *spi,
782 const struct spi_test *testtemplate,
789 struct spi_test test;
790 int i, tx_count, rx_count;
792 /* copy the test template to test */
793 memcpy(&test, testtemplate, sizeof(test));
795 /* if iterate_transfer_mask is not set,
796 * then set it to first transfer only
798 if (!(test.iterate_transfer_mask & (BIT(test.transfer_count) - 1)))
799 test.iterate_transfer_mask = 1;
801 /* count number of transfers with tx/rx_buf != NULL */
802 rx_count = tx_count = 0;
803 for (i = 0; i < test.transfer_count; i++) {
804 if (test.transfers[i].tx_buf)
806 if (test.transfers[i].rx_buf)
810 /* in some iteration cases warn and exit early,
811 * as there is nothing to do, that has not been tested already...
813 if (tx_off && (!tx_count)) {
814 dev_warn_once(&spi->dev,
815 "%s: iterate_tx_off configured with tx_buf==NULL - ignoring\n",
819 if (rx_off && (!rx_count)) {
820 dev_warn_once(&spi->dev,
821 "%s: iterate_rx_off configured with rx_buf==NULL - ignoring\n",
827 if (!(len || tx_off || rx_off)) {
828 dev_info(&spi->dev, "Running test %s\n", test.description);
831 " with iteration values: len = %zu, tx_off = %zu, rx_off = %zu\n",
832 len, tx_off, rx_off);
835 /* update in the values from iteration values */
836 for (i = 0; i < test.transfer_count; i++) {
837 /* only when bit in transfer mask is set */
838 if (!(test.iterate_transfer_mask & BIT(i)))
840 test.transfers[i].len = len;
841 if (test.transfers[i].tx_buf)
842 test.transfers[i].tx_buf += tx_off;
843 if (test.transfers[i].tx_buf)
844 test.transfers[i].rx_buf += rx_off;
848 return _spi_test_run_iter(spi, &test, tx, rx);
852 * spi_test_execute_msg - default implementation to run a test
854 * spi: @spi_device on which to run the @spi_message
855 * test: the test to execute, which already contains @msg
856 * tx: the tx buffer allocated for the test sequence
857 * rx: the rx buffer allocated for the test sequence
859 * Returns: error code of spi_sync as well as basic error checking
861 int spi_test_execute_msg(struct spi_device *spi, struct spi_test *test,
864 struct spi_message *msg = &test->msg;
868 /* only if we do not simulate */
869 if (!simulate_only) {
872 /* dump the complete message before and after the transfer */
873 if (dump_messages == 3)
874 spi_test_dump_message(spi, msg, true);
877 /* run spi message */
878 ret = spi_sync(spi, msg);
879 test->elapsed_time = ktime_to_ns(ktime_sub(ktime_get(), start));
880 if (ret == -ETIMEDOUT) {
882 "spi-message timed out - reruning...\n");
883 /* rerun after a few explicit schedules */
884 for (i = 0; i < 16; i++)
886 ret = spi_sync(spi, msg);
890 "Failed to execute spi_message: %i\n",
895 /* do some extra error checks */
896 if (msg->frame_length != msg->actual_length) {
898 "actual length differs from expected\n");
903 /* run rx-buffer tests */
904 ret = spi_test_check_loopback_result(spi, msg, tx, rx);
908 ret = spi_test_check_elapsed_time(spi, test);
911 /* if requested or on error dump message (including data) */
913 if (dump_messages || ret)
914 spi_test_dump_message(spi, msg,
915 (dump_messages >= 2) || (ret));
919 EXPORT_SYMBOL_GPL(spi_test_execute_msg);
922 * spi_test_run_test - run an individual spi_test
923 * including all the relevant iterations on:
924 * length and buffer alignment
926 * spi: the spi_device to send the messages to
927 * test: the test which we need to execute
928 * tx: the tx buffer allocated for the test sequence
929 * rx: the rx buffer allocated for the test sequence
931 * Returns: status code of spi_sync or other failures
934 int spi_test_run_test(struct spi_device *spi, const struct spi_test *test,
939 size_t tx_align, rx_align;
942 /* test for transfer limits */
943 if (test->transfer_count >= SPI_TEST_MAX_TRANSFERS) {
945 "%s: Exceeded max number of transfers with %i\n",
946 test->description, test->transfer_count);
950 /* setting up some values in spi_message
951 * based on some settings in spi_master
952 * some of this can also get done in the run() method
955 /* iterate over all the iterable values using macros
956 * (to make it a bit more readable...
958 #define FOR_EACH_ALIGNMENT(var) \
960 var < (test->iterate_##var ? \
961 (spi->master->dma_alignment ? \
962 spi->master->dma_alignment : \
963 test->iterate_##var) : \
967 for (idx_len = 0; idx_len < SPI_TEST_MAX_ITERATE &&
968 (len = test->iterate_len[idx_len]) != -1; idx_len++) {
969 FOR_EACH_ALIGNMENT(tx_align) {
970 FOR_EACH_ALIGNMENT(rx_align) {
971 /* and run the iteration */
972 ret = spi_test_run_iter(spi, test,
985 EXPORT_SYMBOL_GPL(spi_test_run_test);
988 * spi_test_run_tests - run an array of spi_messages tests
989 * @spi: the spi device on which to run the tests
990 * @tests: NULL-terminated array of @spi_test
992 * Returns: status errors as per @spi_test_run_test()
995 int spi_test_run_tests(struct spi_device *spi,
996 struct spi_test *tests)
998 char *rx = NULL, *tx = NULL;
999 int ret = 0, count = 0;
1000 struct spi_test *test;
1002 /* allocate rx/tx buffers of 128kB size without devm
1003 * in the hope that is on a page boundary
1005 rx = kzalloc(SPI_TEST_MAX_SIZE_PLUS, GFP_KERNEL);
1011 tx = kzalloc(SPI_TEST_MAX_SIZE_PLUS, GFP_KERNEL);
1017 /* now run the individual tests in the table */
1018 for (test = tests, count = 0; test->description[0];
1020 /* only run test if requested */
1021 if ((run_only_test > -1) && (count != run_only_test))
1023 /* run custom implementation */
1025 ret = test->run_test(spi, test, tx, rx);
1027 ret = spi_test_run_test(spi, test, tx, rx);
1030 /* add some delays so that we can easily
1031 * detect the individual tests when using a logic analyzer
1032 * we also add scheduling to avoid potential spi_timeouts...
1043 EXPORT_SYMBOL_GPL(spi_test_run_tests);