spi: add loopback test driver to allow for spi_master regression tests

This driver is submitting lots of distinct spi-messages messages
with all kinds of alignments and length pattern.
Also distinct kinds of transfer pattern tests are implemented
(rx, tx, rx/tx, tx+tx, tx+rx,...)

Right now on a raspberry pi 752 distinct spi_messages are executed
in 13 different scenarios.

Configuration of additional test-pattern is easy, so that when
new bugs in drivers get detected the relevant transfer pattern can
also get added to the test framework, so that such situations are
detected in other drivers as well.

The idea behind this driver is to make it possible to also detect
regressions in spi_master implementations when changes occur.
Potentially these tests could get executed automatically in a
test-server-farm.
Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-loopback-test.c

+/*
+ *  linux/drivers/spi/spi-loopback-test.c
+ *
+ *  (c) Martin Sperl <kernel@martin.sperl.org>
+ *
+ *  Loopback test driver to test several typical spi_message conditions
+ *  that a spi_master driver may encounter
+ *  this can also get used for regression testing
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ */
+
+#include <linux/delay.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/list_sort.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/printk.h>
+#include <linux/spi/spi.h>
+
+#include "spi-test.h"
+
+/* flag to only simulate transfers */
+int simulate_only;
+module_param(simulate_only, int, 0);
+MODULE_PARM_DESC(simulate_only, "if not 0 do not execute the spi message");
+
+/* dump spi messages */
+int dump_messages;
+module_param(dump_messages, int, 0);
+MODULE_PARM_DESC(dump_message,
+		 "=1 dump the basic spi_message_structure, " \
+		 "=2 dump the spi_message_structure including data, " \
+		 "=3 dump the spi_message structure before and after execution");
+/* the device is jumpered for loopback - enabling some rx_buf tests */
+int loopback;
+module_param(loopback, int, 0);
+MODULE_PARM_DESC(loopback,
+		 "if set enable loopback mode, where the rx_buf "	\
+		 "is checked to match tx_buf after the spi_message "	\
+		 "is executed");
+
+/* run only a specific test */
+int run_only_test = -1;
+module_param(run_only_test, int, 0);
+MODULE_PARM_DESC(run_only_test,
+		 "only run the test with this number (0-based !)");
+
+/* the actual tests to execute */
+static struct spi_test spi_tests[] = {
+	{
+		.description	= "tx/rx-transfer - start of page",
+		.fill_option	= FILL_COUNT_8,
+		.iterate_len    = { ITERATE_MAX_LEN },
+		.iterate_tx_align = ITERATE_ALIGN,
+		.iterate_rx_align = ITERATE_ALIGN,
+		.transfers		= {
+			{
+				.len = 1,
+				.tx_buf = TX(0),
+				.rx_buf = RX(0),
+			},
+		},
+	},
+	{
+		.description	= "tx/rx-transfer - crossing PAGE_SIZE",
+		.fill_option	= FILL_COUNT_8,
+		.iterate_len    = { ITERATE_MAX_LEN },
+		.iterate_tx_align = ITERATE_ALIGN,
+		.iterate_rx_align = ITERATE_ALIGN,
+		.transfers		= {
+			{
+				.len = 1,
+				.tx_buf = TX(PAGE_SIZE - 4),
+				.rx_buf = RX(PAGE_SIZE - 4),
+			},
+		},
+	},
+	{
+		.description	= "tx-transfer - only",
+		.fill_option	= FILL_COUNT_8,
+		.iterate_len    = { ITERATE_MAX_LEN },
+		.iterate_tx_align = ITERATE_ALIGN,
+		.transfers		= {
+			{
+				.len = 1,
+				.tx_buf = TX(0),
+			},
+		},
+	},
+	{
+		.description	= "rx-transfer - only",
+		.fill_option	= FILL_COUNT_8,
+		.iterate_len    = { ITERATE_MAX_LEN },
+		.iterate_rx_align = ITERATE_ALIGN,
+		.transfers		= {
+			{
+				.len = 1,
+				.rx_buf = RX(0),
+			},
+		},
+	},
+	{
+		.description	= "two tx-transfers - alter both",
+		.fill_option	= FILL_COUNT_8,
+		.iterate_len    = { ITERATE_LEN },
+		.iterate_tx_align = ITERATE_ALIGN,
+		.iterate_transfer_mask = BIT(0) | BIT(1),
+		.transfers		= {
+			{
+				.len = 1,
+				.tx_buf = TX(0),
+			},
+			{
+				.len = 1,
+				/* this is why we cant use ITERATE_MAX_LEN */
+				.tx_buf = TX(SPI_TEST_MAX_SIZE_HALF),
+			},
+		},
+	},
+	{
+		.description	= "two tx-transfers - alter first",
+		.fill_option	= FILL_COUNT_8,
+		.iterate_len    = { ITERATE_MAX_LEN },
+		.iterate_tx_align = ITERATE_ALIGN,
+		.iterate_transfer_mask = BIT(1),
+		.transfers		= {
+			{
+				.len = 1,
+				.tx_buf = TX(64),
+			},
+			{
+				.len = 1,
+				.tx_buf = TX(0),
+			},
+		},
+	},
+	{
+		.description	= "two tx-transfers - alter second",
+		.fill_option	= FILL_COUNT_8,
+		.iterate_len    = { ITERATE_MAX_LEN },
+		.iterate_tx_align = ITERATE_ALIGN,
+		.iterate_transfer_mask = BIT(0),
+		.transfers		= {
+			{
+				.len = 16,
+				.tx_buf = TX(0),
+			},
+			{
+				.len = 1,
+				.tx_buf = TX(64),
+			},
+		},
+	},
+	{
+		.description	= "two transfers tx then rx - alter both",
+		.fill_option	= FILL_COUNT_8,
+		.iterate_len    = { ITERATE_MAX_LEN },
+		.iterate_tx_align = ITERATE_ALIGN,
+		.iterate_transfer_mask = BIT(0) | BIT(1),
+		.transfers		= {
+			{
+				.len = 1,
+				.tx_buf = TX(0),
+			},
+			{
+				.len = 1,
+				.rx_buf = RX(0),
+			},
+		},
+	},
+	{
+		.description	= "two transfers tx then rx - alter tx",
+		.fill_option	= FILL_COUNT_8,
+		.iterate_len    = { ITERATE_MAX_LEN },
+		.iterate_tx_align = ITERATE_ALIGN,
+		.iterate_transfer_mask = BIT(0),
+		.transfers		= {
+			{
+				.len = 1,
+				.tx_buf = TX(0),
+			},
+			{
+				.len = 1,
+				.rx_buf = RX(0),
+			},
+		},
+	},
+	{
+		.description	= "two transfers tx then rx - alter rx",
+		.fill_option	= FILL_COUNT_8,
+		.iterate_len    = { ITERATE_MAX_LEN },
+		.iterate_tx_align = ITERATE_ALIGN,
+		.iterate_transfer_mask = BIT(1),
+		.transfers		= {
+			{
+				.len = 1,
+				.tx_buf = TX(0),
+			},
+			{
+				.len = 1,
+				.rx_buf = RX(0),
+			},
+		},
+	},
+	{
+		.description	= "two tx+rx transfers - alter both",
+		.fill_option	= FILL_COUNT_8,
+		.iterate_len    = { ITERATE_LEN },
+		.iterate_tx_align = ITERATE_ALIGN,
+		.iterate_transfer_mask = BIT(0) | BIT(1),
+		.transfers		= {
+			{
+				.len = 1,
+				.tx_buf = TX(0),
+				.rx_buf = RX(0),
+			},
+			{
+				.len = 1,
+				/* making sure we align without overwrite
+				 * the reason we can not use ITERATE_MAX_LEN
+				 */
+				.tx_buf = TX(SPI_TEST_MAX_SIZE_HALF),
+				.rx_buf = RX(SPI_TEST_MAX_SIZE_HALF),
+			},
+		},
+	},
+	{
+		.description	= "two tx+rx transfers - alter first",
+		.fill_option	= FILL_COUNT_8,
+		.iterate_len    = { ITERATE_MAX_LEN },
+		.iterate_tx_align = ITERATE_ALIGN,
+		.iterate_transfer_mask = BIT(0),
+		.transfers		= {
+			{
+				.len = 1,
+				/* making sure we align without overwrite */
+				.tx_buf = TX(1024),
+				.rx_buf = RX(1024),
+			},
+			{
+				.len = 1,
+				/* making sure we align without overwrite */
+				.tx_buf = TX(0),
+				.rx_buf = RX(0),
+			},
+		},
+	},
+	{
+		.description	= "two tx+rx transfers - alter second",
+		.fill_option	= FILL_COUNT_8,
+		.iterate_len    = { ITERATE_MAX_LEN },
+		.iterate_tx_align = ITERATE_ALIGN,
+		.iterate_transfer_mask = BIT(0),
+		.transfers		= {
+			{
+				.len = 1,
+				.tx_buf = TX(0),
+				.rx_buf = RX(0),
+			},
+			{
+				.len = 1,
+				/* making sure we align without overwrite */
+				.tx_buf = TX(1024),
+				.rx_buf = RX(1024),
+			},
+		},
+	},
+
+	{ /* end of tests sequence */ }
+};
+
+static int spi_loopback_test_probe(struct spi_device *spi)
+{
+	int ret;
+
+	dev_info(&spi->dev, "Executing spi-loopback-tests\n");
+
+	ret = spi_test_run_tests(spi, spi_tests);
+
+	dev_info(&spi->dev, "Finished spi-loopback-tests with return: %i\n",
+		 ret);
+
+	return ret;
+}
+
+/* non const match table to permit to change via a module parameter */
+static struct of_device_id spi_loopback_test_of_match[] = {
+	{ .compatible	= "linux,spi-loopback-test", },
+	{ }
+};
+
+/* allow to override the compatible string via a module_parameter */
+module_param_string(compatible, spi_loopback_test_of_match[0].compatible,
+		    sizeof(spi_loopback_test_of_match[0].compatible),
+		    0000);
+
+MODULE_DEVICE_TABLE(of, spi_loopback_test_of_match);
+
+static struct spi_driver spi_loopback_test_driver = {
+	.driver = {
+		.name = "spi-loopback-test",
+		.owner = THIS_MODULE,
+		.of_match_table = spi_loopback_test_of_match,
+	},
+	.probe = spi_loopback_test_probe,
+};
+
+module_spi_driver(spi_loopback_test_driver);
+
+MODULE_AUTHOR("Martin Sperl <kernel@martin.sperl.org>");
+MODULE_DESCRIPTION("test spi_driver to check core functionality");
+MODULE_LICENSE("GPL");
+
+/*-------------------------------------------------------------------------*/
+
+/* spi_test implementation */
+
+#define RANGE_CHECK(ptr, plen, start, slen) \
+	((ptr >= start) && (ptr + plen <= start + slen))
+
+/* we allocate one page more, to allow for offsets */
+#define SPI_TEST_MAX_SIZE_PLUS (SPI_TEST_MAX_SIZE + PAGE_SIZE)
+
+static void spi_test_print_hex_dump(char *pre, const void *ptr, size_t len)
+{
+	/* limit the hex_dump */
+	if (len < 1024) {
+		print_hex_dump(KERN_INFO, pre,
+			       DUMP_PREFIX_OFFSET, 16, 1,
+			       ptr, len, 0);
+		return;
+	}
+	/* print head */
+	print_hex_dump(KERN_INFO, pre,
+		       DUMP_PREFIX_OFFSET, 16, 1,
+		       ptr, 512, 0);
+	/* print tail */
+	pr_info("%s truncated - continuing at offset %04x\n",
+		pre, len - 512);
+	print_hex_dump(KERN_INFO, pre,
+		       DUMP_PREFIX_OFFSET, 16, 1,
+		       ptr + (len - 512), 512, 0);
+}
+
+static void spi_test_dump_message(struct spi_device *spi,
+				  struct spi_message *msg,
+				  bool dump_data)
+{
+	struct spi_transfer *xfer;
+	int i;
+	u8 b;
+
+	dev_info(&spi->dev, "  spi_msg@%pK\n", msg);
+	if (msg->status)
+		dev_info(&spi->dev, "    status:        %i\n",
+			 msg->status);
+	dev_info(&spi->dev, "    frame_length:  %i\n",
+		 msg->frame_length);
+	dev_info(&spi->dev, "    actual_length: %i\n",
+		 msg->actual_length);
+
+	list_for_each_entry(xfer, &msg->transfers, transfer_list) {
+		dev_info(&spi->dev, "    spi_transfer@%pK\n", xfer);
+		dev_info(&spi->dev, "      len:    %i\n", xfer->len);
+		dev_info(&spi->dev, "      tx_buf: %pK\n", xfer->tx_buf);
+		if (dump_data && xfer->tx_buf)
+			spi_test_print_hex_dump("          TX: ",
+						xfer->tx_buf,
+						xfer->len);
+
+		dev_info(&spi->dev, "      rx_buf: %pK\n", xfer->rx_buf);
+		if (dump_data && xfer->rx_buf)
+			spi_test_print_hex_dump("          RX: ",
+						xfer->rx_buf,
+						xfer->len);
+		/* check for unwritten test pattern on rx_buf */
+		if (xfer->rx_buf) {
+			for (i = 0 ; i < xfer->len ; i++) {
+				b = ((u8 *)xfer->rx_buf)[xfer->len - 1 - i];
+				if (b != SPI_TEST_PATTERN_UNWRITTEN)
+					break;
+			}
+			if (i)
+				dev_info(&spi->dev,
+					 "      rx_buf filled with %02x starts at offset: %i\n",
+					 SPI_TEST_PATTERN_UNWRITTEN,
+					 xfer->len - i);
+		}
+	}
+}
+
+struct rx_ranges {
+	struct list_head list;
+	u8 *start;
+	u8 *end;
+};
+
+int rx_ranges_cmp(void *priv, struct list_head *a, struct list_head *b)
+{
+	struct rx_ranges *rx_a = list_entry(a, struct rx_ranges, list);
+	struct rx_ranges *rx_b = list_entry(b, struct rx_ranges, list);
+
+	if (rx_a->start > rx_b->start)
+		return 1;
+	if (rx_a->start < rx_b->start)
+		return -1;
+	return 0;
+}
+
+static int spi_check_rx_ranges(struct spi_device *spi,
+			       struct spi_message *msg,
+			       void *rx)
+{
+	struct spi_transfer *xfer;
+	struct rx_ranges ranges[SPI_TEST_MAX_TRANSFERS], *r;
+	int i = 0;
+	LIST_HEAD(ranges_list);
+	u8 *addr;
+	int ret = 0;
+
+	/* loop over all transfers to fill in the rx_ranges */
+	list_for_each_entry(xfer, &msg->transfers, transfer_list) {
+		/* if there is no rx, then no check is needed */
+		if (!xfer->rx_buf)
+			continue;
+		/* fill in the rx_range */
+		if (RANGE_CHECK(xfer->rx_buf, xfer->len,
+				rx, SPI_TEST_MAX_SIZE_PLUS)) {
+			ranges[i].start = xfer->rx_buf;
+			ranges[i].end = xfer->rx_buf + xfer->len;
+			list_add(&ranges[i].list, &ranges_list);
+			i++;
+		}
+	}
+
+	/* if no ranges, then we can return and avoid the checks...*/
+	if (!i)
+		return 0;
+
+	/* sort the list */
+	list_sort(NULL, &ranges_list, rx_ranges_cmp);
+
+	/* and iterate over all the rx addresses */
+	for (addr = rx; addr < (u8 *)rx + SPI_TEST_MAX_SIZE_PLUS; addr++) {
+		/* if we are the DO not write pattern,
+		 * then continue with the loop...
+		 */
+		if (*addr == SPI_TEST_PATTERN_DO_NOT_WRITE)
+			continue;
+
+		/* check if we are inside a range */
+		list_for_each_entry(r, &ranges_list, list) {
+			/* if so then set to end... */
+			if ((addr >= r->start) && (addr < r->end))
+				addr = r->end;
+		}
+		/* second test after a (hopefull) translation */
+		if (*addr == SPI_TEST_PATTERN_DO_NOT_WRITE)
+			continue;
+
+		/* if still not found then something has modified too much */
+		/* we could list the "closest" transfer here... */
+		dev_err(&spi->dev,
+			"loopback strangeness - rx changed outside of allowed range at: %pK\n",
+			addr);
+		/* do not return, only set ret,
+		 * so that we list all addresses
+		 */
+		ret = -ERANGE;
+	}
+
+	return ret;
+}
+
+static int spi_test_check_loopback_result(struct spi_device *spi,
+					  struct spi_message *msg,
+					  void *tx, void *rx)
+{
+	struct spi_transfer *xfer;
+	u8 rxb, txb;
+	size_t i;
+
+	list_for_each_entry(xfer, &msg->transfers, transfer_list) {
+		/* if there is no rx, then no check is needed */
+		if (!xfer->rx_buf)
+			continue;
+		/* so depending on tx_buf we need to handle things */
+		if (xfer->tx_buf) {
+			for (i = 1; i < xfer->len; i++) {
+				txb = ((u8 *)xfer->tx_buf)[i];
+				rxb = ((u8 *)xfer->rx_buf)[i];
+				if (txb != rxb)
+					goto mismatch_error;
+			}
+		} else {
+			/* first byte received */
+			txb = ((u8 *)xfer->rx_buf)[0];
+			/* first byte may be 0 or xff */
+			if (!((txb == 0) || (txb == 0xff))) {
+				dev_err(&spi->dev,
+					"loopback strangeness - we expect 0x00 or 0xff, but not 0x%02x\n",
+					txb);
+				return -EINVAL;
+			}
+			/* check that all bytes are identical */
+			for (i = 1; i < xfer->len; i++) {
+				rxb = ((u8 *)xfer->rx_buf)[i];
+				if (rxb != txb)
+					goto mismatch_error;
+			}
+		}
+	}
+
+	return spi_check_rx_ranges(spi, msg, rx);
+
+mismatch_error:
+	dev_err(&spi->dev,
+		"loopback strangeness - transfer missmatch on byte %04x - expected 0x%02x, but got 0x%02x\n",
+		i, txb, rxb);
+
+	return -EINVAL;
+}
+
+static int spi_test_translate(struct spi_device *spi,
+			      void **ptr, size_t len,
+			      void *tx, void *rx)
+{
+	size_t off;
+
+	/* return on null */
+	if (!*ptr)
+		return 0;
+
+	/* in the MAX_SIZE_HALF case modify the pointer */
+	if (((size_t)*ptr) & SPI_TEST_MAX_SIZE_HALF)
+		/* move the pointer to the correct range */
+		*ptr += (SPI_TEST_MAX_SIZE_PLUS / 2) -
+			SPI_TEST_MAX_SIZE_HALF;
+
+	/* RX range
+	 * - we check against MAX_SIZE_PLUS to allow for automated alignment
+	 */
+	if (RANGE_CHECK(*ptr, len,  RX(0), SPI_TEST_MAX_SIZE_PLUS)) {
+		off = *ptr - RX(0);
+		*ptr = rx + off;
+
+		return 0;
+	}
+
+	/* TX range */
+	if (RANGE_CHECK(*ptr, len,  TX(0), SPI_TEST_MAX_SIZE_PLUS)) {
+		off = *ptr - TX(0);
+		*ptr = tx + off;
+
+		return 0;
+	}
+
+	dev_err(&spi->dev,
+		"PointerRange [%pK:%pK[ not in range [%pK:%pK[ or [%pK:%pK[\n",
+		*ptr, *ptr + len,
+		RX(0), RX(SPI_TEST_MAX_SIZE),
+		TX(0), TX(SPI_TEST_MAX_SIZE));
+
+	return -EINVAL;
+}
+
+static int spi_test_fill_tx(struct spi_device *spi, struct spi_test *test)
+{
+	struct spi_transfer *xfers = test->transfers;
+	u8 *tx_buf;
+	size_t count = 0;
+	int i, j;
+
+#ifdef __BIG_ENDIAN
+#define GET_VALUE_BYTE(value, index, bytes) \
+	(value >> (8 * (bytes - 1 - count % bytes)))
+#else
+#define GET_VALUE_BYTE(value, index, bytes) \
+	(value >> (8 * (count % bytes)))
+#endif
+
+	/* fill all transfers with the pattern requested */
+	for (i = 0; i < test->transfer_count; i++) {
+		/* if tx_buf is NULL then skip */
+		tx_buf = (u8 *)xfers[i].tx_buf;
+		if (!tx_buf)
+			continue;
+		/* modify all the transfers */
+		for (j = 0; j < xfers[i].len; j++, tx_buf++, count++) {
+			/* fill tx */
+			switch (test->fill_option) {
+			case FILL_MEMSET_8:
+				*tx_buf = test->fill_pattern;
+				break;
+			case FILL_MEMSET_16:
+				*tx_buf = GET_VALUE_BYTE(test->fill_pattern,
+							 count, 2);
+				break;
+			case FILL_MEMSET_24:
+				*tx_buf = GET_VALUE_BYTE(test->fill_pattern,
+							 count, 3);
+				break;
+			case FILL_MEMSET_32:
+				*tx_buf = GET_VALUE_BYTE(test->fill_pattern,
+							 count, 4);
+				break;
+			case FILL_COUNT_8:
+				*tx_buf = count;
+				break;
+			case FILL_COUNT_16:
+				*tx_buf = GET_VALUE_BYTE(count, count, 2);
+				break;
+			case FILL_COUNT_24:
+				*tx_buf = GET_VALUE_BYTE(count, count, 3);
+				break;
+			case FILL_COUNT_32:
+				*tx_buf = GET_VALUE_BYTE(count, count, 4);
+				break;
+			case FILL_TRANSFER_BYTE_8:
+				*tx_buf = j;
+				break;
+			case FILL_TRANSFER_BYTE_16:
+				*tx_buf = GET_VALUE_BYTE(j, j, 2);
+				break;
+			case FILL_TRANSFER_BYTE_24:
+				*tx_buf = GET_VALUE_BYTE(j, j, 3);
+				break;
+			case FILL_TRANSFER_BYTE_32:
+				*tx_buf = GET_VALUE_BYTE(j, j, 4);
+				break;
+			case FILL_TRANSFER_NUM:
+				*tx_buf = i;
+				break;
+			default:
+				dev_err(&spi->dev,
+					"unsupported fill_option: %i\n",
+					test->fill_option);
+				return -EINVAL;
+			}
+		}
+		/* fill rx_buf with SPI_TEST_PATTERN_UNWRITTEN */
+		if (xfers[i].rx_buf)
+			memset(xfers[i].rx_buf, SPI_TEST_PATTERN_UNWRITTEN,
+			       xfers[i].len);
+	}
+
+	return 0;
+}
+
+static int _spi_test_run_iter(struct spi_device *spi,
+			      struct spi_test *test,
+			      void *tx, void *rx)
+{
+	struct spi_message *msg = &test->msg;
+	struct spi_transfer *x;
+	int i, ret;
+
+	/* initialize message - zero-filled via static initialization */
+	spi_message_init_no_memset(msg);
+
+	/* fill rx with the DO_NOT_WRITE pattern */
+	memset(rx, SPI_TEST_PATTERN_DO_NOT_WRITE, SPI_TEST_MAX_SIZE_PLUS);
+
+	/* add the individual transfers */
+	for (i = 0; i < test->transfer_count; i++) {
+		x = &test->transfers[i];
+
+		/* patch the values of tx_buf */
+		ret = spi_test_translate(spi, (void **)&x->tx_buf, x->len,
+					 (void *)tx, rx);
+		if (ret)
+			return ret;
+
+		/* patch the values of rx_buf */
+		ret = spi_test_translate(spi, &x->rx_buf, x->len,
+					 (void *)tx, rx);
+		if (ret)
+			return ret;
+
+		/* and add it to the list */
+		spi_message_add_tail(x, msg);
+	}
+
+	/* fill in the transfer data */
+	ret = spi_test_fill_tx(spi, test);
+	if (ret)
+		return ret;
+
+	/* and execute */
+	if (test->execute_msg)
+		ret = test->execute_msg(spi, test, tx, rx);
+	else
+		ret = spi_test_execute_msg(spi, test, tx, rx);
+
+	/* handle result */
+	if (ret == test->expected_return)
+		return 0;
+
+	dev_err(&spi->dev,
+		"test failed - test returned %i, but we expect %i\n",
+		ret, test->expected_return);
+
+	if (ret)
+		return ret;
+
+	/* if it is 0, as we expected something else,
+	 * then return something special
+	 */
+	return -EFAULT;
+}
+
+static int spi_test_run_iter(struct spi_device *spi,
+			     const struct spi_test *testtemplate,
+			     void *tx, void *rx,
+			     size_t len,
+			     size_t tx_off,
+			     size_t rx_off
+	)
+{
+	struct spi_test test;
+	int i, tx_count, rx_count;
+
+	/* copy the test template to test */
+	memcpy(&test, testtemplate, sizeof(test));
+
+	/* set up test->transfers to the correct count */
+	if (!test.transfer_count) {
+		for (i = 0;
+		    (i < SPI_TEST_MAX_TRANSFERS) && test.transfers[i].len;
+		    i++) {
+			test.transfer_count++;
+		}
+	}
+
+	/* if iterate_transfer_mask is not set,
+	 * then set it to first transfer only
+	 */
+	if (!(test.iterate_transfer_mask & (BIT(test.transfer_count) - 1)))
+		test.iterate_transfer_mask = 1;
+
+	/* count number of transfers with tx/rx_buf != NULL */
+	for (i = 0; i < test.transfer_count; i++) {
+		if (test.transfers[i].tx_buf)
+			tx_count++;
+		if (test.transfers[i].rx_buf)
+			rx_count++;
+	}
+
+	/* in some iteration cases warn and exit early,
+	 * as there is nothing to do, that has not been tested already...
+	 */
+	if (tx_off && (!tx_count)) {
+		dev_warn_once(&spi->dev,
+			      "%s: iterate_tx_off configured with tx_buf==NULL - ignoring\n",
+			      test.description);
+		return 0;
+	}
+	if (rx_off && (!rx_count)) {
+		dev_warn_once(&spi->dev,
+			      "%s: iterate_rx_off configured with rx_buf==NULL - ignoring\n",
+			      test.description);
+		return 0;
+	}
+
+	/* write out info */
+	if (!(len || tx_off || rx_off)) {
+		dev_info(&spi->dev, "Running test %s\n", test.description);
+	} else {
+		dev_info(&spi->dev,
+			 "  with iteration values: len = %i, tx_off = %i, rx_off = %i\n",
+			 len, tx_off, rx_off);
+	}
+
+	/* update in the values from iteration values */
+	for (i = 0; i < test.transfer_count; i++) {
+		/* only when bit in transfer mask is set */
+		if (!(test.iterate_transfer_mask & BIT(i)))
+			continue;
+		if (len)
+			test.transfers[i].len = len;
+		if (test.transfers[i].tx_buf)
+			test.transfers[i].tx_buf += tx_off;
+		if (test.transfers[i].tx_buf)
+			test.transfers[i].rx_buf += rx_off;
+	}
+
+	/* and execute */
+	return _spi_test_run_iter(spi, &test, tx, rx);
+}
+
+/**
+ * spi_test_execute_msg - default implementation to run a test
+ *
+ * spi: @spi_device on which to run the @spi_message
+ * test: the test to execute, which already contains @msg
+ * tx:   the tx buffer allocated for the test sequence
+ * rx:   the rx buffer allocated for the test sequence
+ *
+ * Returns: error code of spi_sync as well as basic error checking
+ */
+int spi_test_execute_msg(struct spi_device *spi, struct spi_test *test,
+			 void *tx, void *rx)
+{
+	struct spi_message *msg = &test->msg;
+	int ret = 0;
+	int i;
+
+	/* only if we do not simulate */
+	if (!simulate_only) {
+		/* dump the complete message before and after the transfer */
+		if (dump_messages == 3)
+			spi_test_dump_message(spi, msg, true);
+
+		/* run spi message */
+		ret = spi_sync(spi, msg);
+		if (ret == -ETIMEDOUT) {
+			dev_info(&spi->dev,
+				 "spi-message timed out - reruning...\n");
+			/* rerun after a few explicit schedules */
+			for (i = 0; i < 16; i++)
+				schedule();
+			ret = spi_sync(spi, msg);
+		}
+		if (ret) {
+			dev_err(&spi->dev,
+				"Failed to execute spi_message: %i\n",
+				ret);
+			goto exit;
+		}
+
+		/* do some extra error checks */
+		if (msg->frame_length != msg->actual_length) {
+			dev_err(&spi->dev,
+				"actual length differs from expected\n");
+			ret = -EIO;
+			goto exit;
+		}
+
+		/* run rx-tests when in loopback mode */
+		if (loopback)
+			ret = spi_test_check_loopback_result(spi, msg,
+							     tx, rx);
+	}
+
+	/* if requested or on error dump message (including data) */
+exit:
+	if (dump_messages || ret)
+		spi_test_dump_message(spi, msg,
+				      (dump_messages >= 2) || (ret));
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(spi_test_execute_msg);
+
+/**
+ * spi_test_run_test - run an individual spi_test
+ *                     including all the relevant iterations on:
+ *                     length and buffer alignment
+ *
+ * spi:  the spi_device to send the messages to
+ * test: the test which we need to execute
+ * tx:   the tx buffer allocated for the test sequence
+ * rx:   the rx buffer allocated for the test sequence
+ *
+ * Returns: status code of spi_sync or other failures
+ */
+
+int spi_test_run_test(struct spi_device *spi, const struct spi_test *test,
+		      void *tx, void *rx)
+{
+	int idx_len;
+	size_t len;
+	size_t tx_align, rx_align;
+	int ret;
+
+	/* test for transfer limits */
+	if (test->transfer_count >= SPI_TEST_MAX_TRANSFERS) {
+		dev_err(&spi->dev,
+			"%s: Exceeded max number of transfers with %i\n",
+			test->description, test->transfer_count);
+		return -E2BIG;
+	}
+
+	/* setting up some values in spi_message
+	 * based on some settings in spi_master
+	 * some of this can also get done in the run() method
+	 */
+
+	/* iterate over all the iterable values using macros
+	 * (to make it a bit more readable...
+	 */
+#define FOR_EACH_ITERATE(var, defaultvalue)				\
+	for (idx_##var = -1, var = defaultvalue;			\
+	     ((idx_##var < 0) ||					\
+		     (							\
+			     (idx_##var < SPI_TEST_MAX_ITERATE) &&	\
+			     (var = test->iterate_##var[idx_##var])	\
+		     )							\
+	     );								\
+	     idx_##var++)
+#define FOR_EACH_ALIGNMENT(var)						\
+	for (var = 0;							\
+	    var < (test->iterate_##var ?				\
+			(spi->master->dma_alignment ?			\
+			 spi->master->dma_alignment :			\
+			 test->iterate_##var) :				\
+			1);						\
+	    var++)
+
+	FOR_EACH_ITERATE(len, 0) {
+		FOR_EACH_ALIGNMENT(tx_align) {
+			FOR_EACH_ALIGNMENT(rx_align) {
+				/* and run the iteration */
+				ret = spi_test_run_iter(spi, test,
+							tx, rx,
+							len,
+							tx_align,
+							rx_align);
+				if (ret)
+					return ret;
+			}
+		}
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(spi_test_run_test);
+
+/**
+ * spi_test_run_tests - run an array of spi_messages tests
+ * @spi: the spi device on which to run the tests
+ * @tests: NULL-terminated array of @spi_test
+ *
+ * Returns: status errors as per @spi_test_run_test()
+ */
+
+int spi_test_run_tests(struct spi_device *spi,
+		       struct spi_test *tests)
+{
+	char *rx = NULL, *tx = NULL;
+	int ret = 0, count = 0;
+	struct spi_test *test;
+
+	/* allocate rx/tx buffers of 128kB size without devm
+	 * in the hope that is on a page boundary
+	 */
+	rx = kzalloc(SPI_TEST_MAX_SIZE_PLUS, GFP_KERNEL);
+	if (!rx) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	tx = kzalloc(SPI_TEST_MAX_SIZE_PLUS, GFP_KERNEL);
+	if (!tx) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	/* now run the individual tests in the table */
+	for (test = tests, count = 0; test->description[0];
+	     test++, count++) {
+		/* only run test if requested */
+		if ((run_only_test > -1) && (count != run_only_test))
+			continue;
+		/* run custom implementation */
+		if (test->run_test)
+			ret = test->run_test(spi, test, tx, rx);
+		else
+			ret = spi_test_run_test(spi, test, tx, rx);
+		if (ret)
+			goto out;
+		/* add some delays so that we can easily
+		 * detect the individual tests when using a logic analyzer
+		 * we also add scheduling to avoid potential spi_timeouts...
+		 */
+		mdelay(100);
+		schedule();
+	}
+
+out:
+	kfree(rx);
+	kfree(tx);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(spi_test_run_tests);

drivers/spi/spi-test.h

+/*
+ *  linux/drivers/spi/spi-test.h
+ *
+ *  (c) Martin Sperl <kernel@martin.sperl.org>
+ *
+ *  spi_test definitions
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ */
+
+#include <linux/spi/spi.h>
+
+#define SPI_TEST_MAX_TRANSFERS 4
+#define SPI_TEST_MAX_SIZE (32 * PAGE_SIZE)
+#define SPI_TEST_MAX_ITERATE 16
+
+/* the "dummy" start addresses used in spi_test
+ * these addresses get translated at a later stage
+ */
+#define RX_START	BIT(30)
+#define TX_START	BIT(31)
+#define RX(off)		((void *)(RX_START + off))
+#define TX(off)		((void *)(TX_START + off))
+
+/* some special defines for offsets */
+#define SPI_TEST_MAX_SIZE_HALF	BIT(29)
+
+/* detection pattern for unfinished reads...
+ * - 0x00 or 0xff could be valid levels for tx_buf = NULL,
+ * so we do not use either of them
+ */
+#define SPI_TEST_PATTERN_UNWRITTEN 0xAA
+#define SPI_TEST_PATTERN_DO_NOT_WRITE 0x55
+#define SPI_TEST_CHECK_DO_NOT_WRITE 64
+
+/**
+ * struct spi_test - describes a specific (set of) tests to execute
+ *
+ * @description:      description of the test
+ *
+ * @msg:              a template @spi_message usedfor the default settings
+ * @transfers:        array of @spi_transfers that are part of the
+ *                    resulting spi_message. The first transfer with len == 0
+ *                    signifies the end of the list
+ * @transfer_count:   normally computed number of transfers with len > 0
+ *
+ * @run_test:         run a specific spi_test - this allows to override
+ *                    the default implementation of @spi_test_run_transfer
+ *                    either to add some custom filters for a specific test
+ *                    or to effectively run some very custom tests...
+ * @execute_msg:      run the spi_message for real - this allows to override
+ *                    @spi_test_execute_msg to apply final modifications
+ *                    on the spi_message
+ * @expected_return:  the expected return code - in some cases we want to
+ *                    test also for error conditions
+ *
+ * @iterate_len:      list of length to iterate on (in addition to the
+ *                    explicitly set @spi_transfer.len)
+ * @iterate_tx_align: change the alignment of @spi_transfer.tx_buf
+ *                    for all values in the below range if set.
+ *                    the ranges are:
+ *                    [0 : @spi_master.dma_alignment[ if set
+ *                    [0 : iterate_tx_align[ if unset
+ * @iterate_rx_align: change the alignment of @spi_transfer.rx_buf
+ *                    see @iterate_tx_align for details
+ * @iterate_transfer_mask: the bitmask of transfers to which the iterations
+ *                         apply - if 0, then it applies to all transfer
+ *
+ * @fill_option:      define the way how tx_buf is filled
+ * @fill_pattern:     fill pattern to apply to the tx_buf
+ *                    (used in some of the @fill_options)
+ */
+
+struct spi_test {
+	char description[64];
+	struct spi_message msg;
+	struct spi_transfer transfers[SPI_TEST_MAX_TRANSFERS];
+	unsigned int transfer_count;
+	int (*run_test)(struct spi_device *spi, struct spi_test *test,
+			void *tx, void *rx);
+	int (*execute_msg)(struct spi_device *spi, struct spi_test *test,
+			   void *tx, void *rx);
+	int expected_return;
+	/* iterate over all the non-zero values */
+	int iterate_len[SPI_TEST_MAX_ITERATE];
+	int iterate_tx_align;
+	int iterate_rx_align;
+	u32 iterate_transfer_mask;
+	/* the tx-fill operation */
+	u32 fill_option;
+#define FILL_MEMSET_8	0	/* just memset with 8 bit */
+#define FILL_MEMSET_16	1	/* just memset with 16 bit */
+#define FILL_MEMSET_24	2	/* just memset with 24 bit */
+#define FILL_MEMSET_32	3	/* just memset with 32 bit */
+#define FILL_COUNT_8	4	/* fill with a 8 byte counter */
+#define FILL_COUNT_16	5	/* fill with a 16 bit counter */
+#define FILL_COUNT_24	6	/* fill with a 24 bit counter */
+#define FILL_COUNT_32	7	/* fill with a 32 bit counter */
+#define FILL_TRANSFER_BYTE_8  8	/* fill with the transfer byte - 8 bit */
+#define FILL_TRANSFER_BYTE_16 9	/* fill with the transfer byte - 16 bit */
+#define FILL_TRANSFER_BYTE_24 10 /* fill with the transfer byte - 24 bit */
+#define FILL_TRANSFER_BYTE_32 11 /* fill with the transfer byte - 32 bit */
+#define FILL_TRANSFER_NUM     16 /* fill with the transfer number */
+	u32 fill_pattern;
+};
+
+/* default implementation for @spi_test.run_test */
+int spi_test_run_test(struct spi_device *spi,
+		      const struct spi_test *test,
+		      void *tx, void *rx);
+
+/* default implementation for @spi_test.execute_msg */
+int spi_test_execute_msg(struct spi_device *spi,
+			 struct spi_test *test,
+			 void *tx, void *rx);
+
+/* function to execute a set of tests */
+int spi_test_run_tests(struct spi_device *spi,
+		       struct spi_test *tests);
+
+/* some of the default @spi_transfer.len to test */
+#define ITERATE_LEN 16, 32, 64, 128, 256, 1024, PAGE_SIZE, 65536
+
+#define ITERATE_MAX_LEN ITERATE_LEN, SPI_TEST_MAX_SIZE
+
+/* the default alignment to test */
+#define ITERATE_ALIGN sizeof(int)