mtd-utils: Add nand flash bit errors test

Basically a user space port of the mtd speed test kernel module.
In addition to the module parameters, the utility can resture
the block contents after test and allows setting the maxium writes
for the test.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
Signed-off-by: Richard Weinberger <richard@nod.at>

2 files changed, 521 insertions, 1 deletions

diff --git a/tests/mtd-tests/Makemodule.am b/tests/mtd-tests/Makemodule.am
index ac40697..38b419f 100644
--- a/tests/mtd-tests/Makemodule.am
+++ b/tests/mtd-tests/Makemodule.am
@@ -10,8 +10,12 @@ flash_speed_SOURCES = tests/mtd-tests/flash_speed.c
 flash_speed_LDADD = libmtd.a
 flash_speed_CPPFLAGS = $(AM_CPPFLAGS)
 
+nandbiterrs_SOURCES = tests/mtd-tests/nandbiterrs.c
+nandbiterrs_LDADD = libmtd.a
+nandbiterrs_CPPFLAGS = $(AM_CPPFLAGS)
+
 MTDTEST_BINS = \
-	flash_torture flash_stress flash_speed
+	flash_torture flash_stress flash_speed nandbiterrs
 
 if INSTALL_TESTS
 pkglibexec_PROGRAMS += $(MTDTEST_BINS)
diff --git a/tests/mtd-tests/nandbiterrs.c b/tests/mtd-tests/nandbiterrs.c
new file mode 100644
index 0000000..6acbfee
--- /dev/null
+++ b/tests/mtd-tests/nandbiterrs.c
@@ -0,0 +1,516 @@
+/*
+ * Copyright © 2012 NetCommWireless
+ * Iwo Mergler <Iwo.Mergler@netcommwireless.com.au>
+ *
+ * Copyright © 2015 sigma star gmbh
+ * David Oberhollenzer <david.oberhollenzer@sigma-star.at>
+ *
+ * Test for multi-bit error recovery on a NAND page. This mostly tests the
+ * ECC controller / driver.
+ *
+ * There are two test modes:
+ *
+ *	0 - artificially inserting bit errors until the ECC fails
+ *	    This is the default method and fairly quick. It should
+ *	    be independent of the quality of the FLASH.
+ *
+ *	1 - re-writing the same pattern repeatedly until the ECC fails.
+ *	    This method relies on the physics of NAND FLASH to eventually
+ *	    generate '0' bits if '1' has been written sufficient times.
+ *	    Depending on the NAND, the first bit errors will appear after
+ *	    1000 or more writes and then will usually snowball, reaching the
+ *	    limits of the ECC quickly.
+ *
+ *	    The test stops after 10000 cycles, should your FLASH be
+ *	    exceptionally good and not generate bit errors before that. Try
+ *	    a different page in that case.
+ *
+ * Please note that neither of these tests will significantly 'use up' any
+ * FLASH endurance. Only a maximum of two erase operations will be performed.
+ *
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; see the file COPYING. If not, write to the Free Software
+ * Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+#define PROGRAM_NAME "nandbiterrs"
+
+#include <mtd/mtd-user.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+#include <string.h>
+#include <stdlib.h>
+#include <libmtd.h>
+#include <getopt.h>
+#include <stdio.h>
+#include <fcntl.h>
+
+#include "common.h"
+
+/* We don't expect more than this many correctable bit errors per page. */
+#define MAXBITS 512
+
+#define KEEP_CONTENTS 0x01
+#define MODE_INCREMENTAL 0x02
+#define MODE_OVERWRITE 0x04
+
+static int peb = -1, page = -1, max_overwrite = -1, seed = -1;
+static const char *mtddev;
+
+static unsigned char *wbuffer, *rbuffer, *old_data;
+static int fd, pagesize, pagecount, flags;
+static struct mtd_dev_info mtd;
+static libmtd_t mtd_desc;
+
+static const struct option options[] = {
+	{ "help", no_argument, NULL, 'h' },
+	{ "keep", no_argument, NULL, 'k' },
+	{ "peb", required_argument, NULL, 'b' },
+	{ "page", required_argument, NULL, 'p' },
+	{ "seed", required_argument, NULL, 's' },
+	{ "writes", required_argument, NULL, 'w' },
+	{ "incremental", no_argument, NULL, 'i' },
+	{ "overwrite", no_argument, NULL, 'o' },
+	{ NULL, 0, NULL, 0 },
+};
+
+static void usage(int status)
+{
+	fputs(
+	"Usage: "PROGRAM_NAME" [OPTIONS] <device>\n\n"
+	"Common options:\n"
+	"  -h, --help          Display this help output\n"
+	"  -k, --keep          Restore existing contents after test\n"
+	"  -b, --peb <num>     Use this physical erase block\n"
+	"  -p, --page <num>    Use this page within the erase block\n"
+	"  -s, --seed <num>    Specify seed for PRNG\n\n"
+	"Options controling test mode:\n"
+	"  -i, --incremental   Manually insert bit errors until ECC fails\n"
+	"  -o, --overwrite     Rewrite page until bits flip and ECC fails\n\n"
+	"Test mode specific options:\n"
+	"  -w, --writes <num>  Number of writes (default 10000)\n",
+	status==EXIT_SUCCESS ? stdout : stderr);
+	exit(status);
+}
+
+static long read_num(int opt, const char *arg)
+{
+	char *end;
+	long num;
+
+	num = strtol(arg, &end, 0);
+
+	if (!end || *end != '\0') {
+		fprintf(stderr, "-%c: expected integer argument\n", opt);
+		exit(EXIT_FAILURE);
+	}
+	return num;
+}
+
+static void process_options(int argc, char **argv)
+{
+	int c;
+
+	while (1) {
+		c = getopt_long(argc, argv, "hkb:p:s:iow:", options, NULL);
+		if (c == -1)
+			break;
+
+		switch (c) {
+		case 'k':
+			if (flags & KEEP_CONTENTS)
+				goto failmulti;
+			flags |= KEEP_CONTENTS;
+			break;
+		case 'b':
+			if (peb >= 0)
+				goto failmulti;
+			peb = read_num(c, optarg);
+			if (peb < 0)
+				goto failarg;
+			break;
+		case 'i':
+			if (flags & (MODE_INCREMENTAL|MODE_OVERWRITE))
+				goto failmultimode;
+			flags |= MODE_INCREMENTAL;
+			break;
+		case 'o':
+			if (flags & (MODE_INCREMENTAL|MODE_OVERWRITE))
+				goto failmultimode;
+			flags |= MODE_OVERWRITE;
+			break;
+		case 'w':
+			if (max_overwrite > 0)
+				goto failmulti;
+			max_overwrite = read_num(c, optarg);
+			if (max_overwrite <= 0)
+				goto failarg;
+			break;
+		case 's':
+			if (seed >= 0)
+				goto failmulti;
+			seed = read_num(c, optarg);
+			if (seed < 0)
+				goto failarg;
+			break;
+		case 'p':
+			if (page > 0)
+				goto failmulti;
+			page = read_num(c, optarg);
+			if (page < 0)
+				goto failarg;
+			break;
+		case 'h':
+			usage(EXIT_SUCCESS);
+		default:
+			exit(EXIT_FAILURE);
+		}
+	}
+
+	if (optind < argc)
+		mtddev = argv[optind++];
+	else
+		errmsg_die("No device specified!\n");
+
+	if (optind < argc)
+		usage(EXIT_FAILURE);
+
+	if (!(flags & (MODE_OVERWRITE|MODE_INCREMENTAL)))
+		errmsg_die("No test mode specified!");
+
+	if ((max_overwrite > 0) && !(flags & MODE_OVERWRITE))
+		errmsg_die("Write count specified but mode is not --overwrite!");
+
+	if (max_overwrite < 0)
+		max_overwrite = 10000;
+	if (peb < 0)
+		peb = 0;
+	if (page < 0)
+		page = 0;
+	if (seed < 0)
+		seed = 0;
+	return;
+failmultimode:
+	errmsg_die("Test mode specified more than once!");
+failmulti:
+	errmsg_die("'-%c' specified more than once!", c);
+failarg:
+	errmsg_die("Invalid argument for '-%c'!", c);
+}
+
+/* 'random' bytes from known offsets */
+static unsigned char hash(unsigned int offset)
+{
+	unsigned int v = offset;
+	unsigned char c;
+	v ^= 0x7f7edfd3;
+	v = v ^ (v >> 3);
+	v = v ^ (v >> 5);
+	v = v ^ (v >> 13);
+	c = v & 0xFF;
+	/* Reverse bits of result. */
+	c = (c & 0x0F) << 4 | (c & 0xF0) >> 4;
+	c = (c & 0x33) << 2 | (c & 0xCC) >> 2;
+	c = (c & 0x55) << 1 | (c & 0xAA) >> 1;
+	return c;
+}
+
+static int write_page(void)
+{
+	int err;
+
+	err = mtd_write(mtd_desc, &mtd, fd, peb, page*pagesize,
+					wbuffer, pagesize, NULL, 0, 0);
+
+	if (err)
+		fprintf(stderr, "Failed to write page %d in block %d\n", peb, page);
+
+	return err;
+}
+
+static int rewrite_page(void)
+{
+	if (ioctl(fd, MTDFILEMODE, MTD_FILE_MODE_RAW) != 0)
+		goto fail_mode;
+
+	if (write_page() != 0)
+		return -1;
+
+	if (ioctl(fd, MTDFILEMODE, MTD_FILE_MODE_NORMAL) != 0)
+		goto fail_mode;
+
+	return 0;
+fail_mode:
+	perror("MTDFILEMODE");
+	return -1;
+}
+
+static int read_page(void)
+{
+	struct mtd_ecc_stats old, new;
+	int err = 0;
+
+	if (ioctl(fd, ECCGETSTATS, &old) != 0)
+		goto failstats;
+
+	err = mtd_read(&mtd, fd, peb, page*pagesize, rbuffer, pagesize);
+	if (err) {
+		fputs("Read failed!\n", stderr);
+		return -1;
+	}
+
+	if (new.failed > old.failed) {
+		fprintf(stderr, "Failed to recover %d bitflips\n",
+				new.failed - old.failed);
+		return -1;
+	}
+
+	if (ioctl(fd, ECCGETSTATS, &new) != 0)
+		goto failstats;
+
+	return new.corrected - old.corrected;
+failstats:
+	perror("ECCGETSTATS");
+	return -1;
+}
+
+static int verify_page(void)
+{
+	unsigned int i, errs = 0;
+
+	for (i = 0; i < pagesize; ++i) {
+		if (rbuffer[i] != hash(i+seed))
+			++errs;
+	}
+
+	if (errs)
+		fputs("ECC failure, invalid data despite read success\n", stderr);
+
+	return errs;
+}
+
+/* Finds the first '1' bit in wbuffer and sets it to '0'. */
+static int insert_biterror(void)
+{
+	int bit, mask, byte;
+
+	for (byte = 0; byte < pagesize; ++byte) {
+		for (bit = 7, mask = 0x80; bit >= 0; bit--, mask>>=0) {
+			if (wbuffer[byte] & mask) {
+				wbuffer[byte] &= ~mask;
+				printf("Inserted biterror @ %u/%u\n", byte, bit);
+				return 0;
+			}
+		}
+		++byte;
+	}
+	fputs("biterror: Failed to find a '1' bit\n", stderr);
+	return -1;
+}
+
+/* Writes 'random' data to page and then introduces deliberate bit
+ * errors into the page, while verifying each step. */
+static int incremental_errors_test(void)
+{
+	unsigned int i, errs_per_subpage = 0;
+	int count = 0;
+
+	puts("incremental biterrors test");
+
+	for (i = 0; i < pagesize; ++i)
+		wbuffer[i] = hash(i+seed);
+
+	if (write_page() != 0)
+		return -1;
+
+	for (errs_per_subpage = 0; ; ++errs_per_subpage) {
+		if (rewrite_page() != 0)
+			return -1;
+
+		count = read_page();
+		if (count > 0)
+			printf("Read reported %d corrected bit errors\n", count);
+		if (count < 0) {
+			fprintf(stderr, "Read error after %d bit errors per page\n",
+				errs_per_subpage);
+			return 0;
+		}
+
+		if (verify_page() != 0)
+			return -1;
+
+		printf("Successfully corrected %d bit errors per subpage\n",
+			errs_per_subpage);
+
+		if (insert_biterror() != 0)
+			return -1;
+	}
+
+	return 0;
+}
+
+
+/* Writes 'random' data to page and then re-writes that same data repeatedly.
+   This eventually develops bit errors (bits written as '1' will slowly become
+   '0'), which are corrected as far as the ECC is capable of. */
+static int overwrite_test(void)
+{
+	unsigned int i, max_corrected = 0, opno;
+	unsigned int bitstats[MAXBITS]; /* bit error histogram. */
+	int err = 0;
+
+	memset(bitstats, 0, sizeof(bitstats));
+
+	puts("overwrite biterrors test");
+
+	for (i = 0; i < pagesize; ++i)
+		wbuffer[i] = hash(i+seed);
+
+	if (write_page() != 0)
+		return -1;
+
+	for (opno = 0; opno < max_overwrite; ++opno) {
+		err = write_page();
+		if (err)
+			break;
+
+		err = read_page();
+		if (err >= 0) {
+			if (err >= MAXBITS) {
+				puts("Implausible number of bit errors corrected");
+				err = -1;
+				break;
+			}
+			bitstats[err]++;
+			if (err > max_corrected) {
+				max_corrected = err;
+				printf("Read reported %d corrected bit errors\n", err);
+			}
+		} else {
+			err = 0;
+			break;
+		}
+
+		err = verify_page();
+		if (err) {
+			bitstats[max_corrected] = opno;
+			break;
+		}
+	}
+
+	/* At this point bitstats[0] contains the number of ops with no bit
+	 * errors, bitstats[1] the number of ops with 1 bit error, etc. */
+	printf("Bit error histogram (%d operations total):\n", opno);
+	for (i = 0; i < max_corrected; ++i) {
+		printf("Page reads with %3d corrected bit errors: %d\n",
+			i, bitstats[i]);
+	}
+	return err;
+}
+
+int main(int argc, char **argv)
+{
+	int err = 0, status = EXIT_FAILURE;
+
+	process_options(argc, argv);
+
+	mtd_desc = libmtd_open();
+	if (!mtd_desc)
+		return errmsg("can't initialize libmtd");
+
+	if (mtd_get_dev_info(mtd_desc, mtddev, &mtd) < 0)
+		return errmsg("mtd_get_dev_info failed");
+
+	if (mtd.type!=MTD_MLCNANDFLASH && mtd.type!=MTD_NANDFLASH)
+		return errmsg("%s is not a NAND flash!", mtddev);
+
+	pagesize = mtd.subpage_size;
+	pagecount = mtd.eb_size / pagesize;
+
+	if (peb >= mtd.eb_cnt)
+		return errmsg("Physical erase block %d is out of range!", peb);
+	if (page >= pagecount)
+		return errmsg("Page number %d is out of range!", page);
+	if ((fd = open(mtddev, O_RDWR)) == -1) {
+		perror(mtddev);
+		return EXIT_FAILURE;
+	}
+
+	if (flags & KEEP_CONTENTS) {
+		old_data = malloc(mtd.eb_size);
+		if (!old_data) {
+			perror(NULL);
+			goto fail_dev;
+		}
+		if (mtd_read(&mtd, fd, peb, 0, old_data, mtd.eb_size)) {
+			fprintf(stderr, "Reading erase block %d failed!\n", peb);
+			goto fail_dev;
+		}
+	}
+
+	wbuffer = malloc(pagesize);
+	if (!wbuffer) {
+		perror(NULL);
+		goto fail_dev;
+	}
+
+	rbuffer = malloc(pagesize);
+	if (!rbuffer) {
+		perror(NULL);
+		goto fail_rbuffer;
+	}
+
+	if (mtd_erase(mtd_desc, &mtd, fd, peb)) {
+		fprintf(stderr, "Cannot erase block %d\n", peb);
+		goto fail_test;
+	}
+
+	if (flags & MODE_INCREMENTAL)
+		err = incremental_errors_test();
+	else if (flags & MODE_OVERWRITE)
+		err = overwrite_test();
+
+	status = err ? EXIT_FAILURE : EXIT_SUCCESS;
+
+	if (flags & KEEP_CONTENTS) {
+		if (mtd_erase(mtd_desc, &mtd, fd, peb)) {
+			fprintf(stderr, "Restoring: Cannot erase block %d\n", peb);
+			status = EXIT_FAILURE;
+			goto fail_test;
+		}
+
+		err = mtd_write(mtd_desc, &mtd, fd, peb, 0,
+					old_data, mtd.eb_size, NULL, 0, 0);
+
+		if (err) {
+			fputs("Failed restoring old block contents!\n", stderr);
+			status = EXIT_FAILURE;
+		}
+	} else {
+		/* We leave the block un-erased in case of test failure. */
+		if (err)
+			goto fail_test;
+
+		if (mtd_erase(mtd_desc, &mtd, fd, peb)) {
+			fprintf(stderr, "Cannot erase block %d\n", peb);
+			status = EXIT_FAILURE;
+		}
+	}
+fail_test:
+	free(rbuffer);
+fail_rbuffer:
+	free(wbuffer);
+fail_dev:
+	close(fd);
+	free(old_data);
+	return status;
+}