Test for multi-bit error correction

Message ID	6871BC8982B258468985EE735D2C57524E269AFB60@ntcex01.corp.netcomm.com.au
State	New, archived
Headers	show Return-Path: <linux-mtd-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org> From: Iwo Mergler <Iwo.Mergler@netcommwireless.com> To: "dedekind1@gmail.com" <dedekind1@gmail.com> Date: Fri, 31 Aug 2012 08:59:48 +1000 Subject: RE: [PATCH] Test for multi-bit error correction Message-ID: <6871BC8982B258468985EE735D2C57524E269AFB60@ntcex01.corp.netcomm.com.au> References: <6871BC8982B258468985EE735D2C57524E269AFB52@ntcex01.corp.netcomm.com.au> ,<1346310033.2848.536.camel@sauron.fi.intel.com> <6871BC8982B258468985EE735D2C57524E269AFB54@ntcex01.corp.netcomm.com.au>, <1346315075.2848.538.camel@sauron.fi.intel.com> In-Reply-To: <1346315075.2848.538.camel@sauron.fi.intel.com> Content-Language: en-AU MIME-Version: 1.0 summary: Content analysis details: (-4.2 points) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at http://www.dnswl.org/, medium trust [216.82.253.227 listed in list.dnswl.org] -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] Cc: "linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org> Precedence: list Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: linux-mtd-bounces@lists.infradead.org Errors-To: linux-mtd-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org

diff --git a/drivers/mtd/tests/Makefile b/drivers/mtd/tests/Makefile index b44dcab..bd0065c 100644 --- a/drivers/mtd/tests/Makefile +++ b/drivers/mtd/tests/Makefile @@ -6,3 +6,4 @@ obj-$(CONFIG_MTD_TESTS) += mtd_stresstest.o obj-$(CONFIG_MTD_TESTS) += mtd_subpagetest.o obj-$(CONFIG_MTD_TESTS) += mtd_torturetest.o obj-$(CONFIG_MTD_TESTS) += mtd_nandecctest.o +obj-$(CONFIG_MTD_TESTS) += mtd_nandbiterrs.o diff --git a/drivers/mtd/tests/mtd_nandbiterrs.c b/drivers/mtd/tests/mtd_nandbiterrs.c new file mode 100644 index 0000000..94e908e --- /dev/null +++ b/drivers/mtd/tests/mtd_nandbiterrs.c @@ -0,0 +1,460 @@ +/* + * (C)2012 NetCommWireless + * Iwo Mergler <Iwo.Mergler@netcommwireless.com.au> + * + * 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. + */ +#include <linux/init.h> +#include <linux/module.h> +#include <linux/moduleparam.h> +#include <linux/mtd/mtd.h> +#include <linux/err.h> +#include <linux/mtd/nand.h> +#include <linux/slab.h> + +#define msg(FMT, VA...) pr_info("mtd_nandbiterrs: "FMT, ##VA) + +static int dev; +module_param(dev, int, S_IRUGO); +MODULE_PARM_DESC(dev, "MTD device number to use"); + +static unsigned page_offset; +module_param(page_offset, uint, S_IRUGO); +MODULE_PARM_DESC(page_offset, "Page number relative to dev start"); + +static unsigned seed; +module_param(seed, uint, S_IRUGO); +MODULE_PARM_DESC(seed, "Random seed"); + +static int mode; +module_param(mode, int, S_IRUGO); +MODULE_PARM_DESC(mode, "0=incremental errors, 1=overwrite test"); + +static unsigned max_overwrite = 10000; + +static loff_t offset; /* Offset of the page we're using. */ +static unsigned eraseblock; /* Eraseblock number for our page. */ + +/* We assume that the ECC can correct up to a certain number + * of biterrors per subpage. */ +static unsigned subsize; /* Size of subpages */ +static unsigned subcount; /* Number of subpages per page */ + +static struct mtd_info *mtd; /* MTD device */ + +static uint8_t *wbuffer; /* One page write / compare buffer */ +static uint8_t *rbuffer; /* One page read buffer */ + +/* 'random' bytes from known offsets */ +static uint8_t hash(unsigned offset) +{ + unsigned 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 erase_block(void) +{ + int err; + struct erase_info ei; + loff_t addr = eraseblock * mtd->erasesize; + + msg("erase_block\n"); + + memset(&ei, 0, sizeof(struct erase_info)); + ei.mtd = mtd; + ei.addr = addr; + ei.len = mtd->erasesize; + + err = mtd_erase(mtd, &ei); + if (err || ei.state == MTD_ERASE_FAILED) { + msg("error %d while erasing\n", err); + if (!err) + err = -EIO; + return err; + } + + return 0; +} + +/* Writes wbuffer to page */ +static int write_page(int log) +{ + int err = 0; + size_t written; + + if (log) + msg("write_page\n"); + + err = mtd_write(mtd, offset, mtd->writesize, &written, wbuffer); + if (err || written != mtd->writesize) { + msg("error: write failed at %#llx\n", (long long)offset); + if (!err) + err = -EIO; + } + + return err; +} + +/* Re-writes the data area while leaving the OOB alone. */ +static int rewrite_page(int log) +{ + int err = 0; + struct mtd_oob_ops ops; + + if (log) + msg("rewrite page\n"); + + ops.mode = MTD_OPS_RAW; /* No ECC */ + ops.len = mtd->writesize; + ops.retlen = 0; + ops.ooblen = 0; + ops.oobretlen = 0; + ops.ooboffs = 0; + ops.datbuf = wbuffer; + ops.oobbuf = NULL; + + err = mtd_write_oob(mtd, offset, &ops); + if (err || ops.retlen != mtd->writesize) { + msg("error: write_oob failed (%d)\n", err); + if (!err) + err = -EIO; + } + + return err; +} + +/* Reads page into rbuffer. Returns number of corrected bit errors (>=0) + * or error (<0) */ +static int read_page(int log) +{ + int err = 0; + size_t read; + struct mtd_ecc_stats oldstats; + + if (log) + msg("read_page\n"); + + /* Saving last mtd stats */ + memcpy(&oldstats, &mtd->ecc_stats, sizeof(oldstats)); + + err = mtd_read(mtd, offset, mtd->writesize, &read, rbuffer); + if (err == -EUCLEAN) + err = mtd->ecc_stats.corrected - oldstats.corrected; + + if (err < 0 || read != mtd->writesize) { + msg("error: read failed at %#llx\n", (long long)offset); + if (err >= 0) + err = -EIO; + } + + return err; +} + +/* Verifies rbuffer against random sequence */ +static int verify_page(int log) +{ + unsigned i, errs = 0; + + if (log) + msg("verify_page\n"); + + for (i = 0; i < mtd->writesize; i++) { + if (rbuffer[i] != hash(i+seed)) { + msg("Error: page offset %u, expected %02x, got %02x\n", + i, hash(i+seed), rbuffer[i]); + errs++; + } + } + + if (errs) + return -EIO; + else + return 0; +} + +#define CBIT(v, n) ((v) & (1 << (n))) +#define BCLR(v, n) ((v) = (v) & ~(1 << (n))) + +/* Finds the first '1' bit in wbuffer starting at offset 'byte' + * and sets it to '0'. */ +static int insert_biterror(unsigned byte) +{ + int bit; + + while (byte < mtd->writesize) { + for (bit = 7; bit >= 0; bit--) { + if (CBIT(wbuffer[byte], bit)) { + BCLR(wbuffer[byte], bit); + msg("Inserted biterror @ %u/%u\n", byte, bit); + return 0; + } + } + byte++; + } + msg("biterror: Failed to find a '1' bit\n"); + return -EIO; +} + +/* Writes 'random' data to page and then introduces deliberate bit + * errors into the page, while verifying each step. */ +static int incremental_errors_test(void) +{ + int err = 0; + unsigned i; + unsigned errs_per_subpage = 0; + + msg("incremental biterrors test\n"); + + for (i = 0; i < mtd->writesize; i++) + wbuffer[i] = hash(i+seed); + + err = write_page(1); + if (err) + goto exit; + + while (1) { + + err = rewrite_page(1); + if (err) + goto exit; + + err = read_page(1); + if (err > 0) + msg("Read reported %d corrected bit errors\n", err); + if (err < 0) { + msg("After %d biterrors per subpage, read reported error %d\n", + errs_per_subpage, err); + err = 0; + goto exit; + } + + err = verify_page(1); + if (err) { + msg("ECC failure, read data is incorrect despite read success\n"); + goto exit; + } + + msg("Successfully corrected %d bit errors per subpage\n", + errs_per_subpage); + + for (i = 0; i < subcount; i++) { + err = insert_biterror(i * subsize); + if (err < 0) + goto exit; + } + errs_per_subpage++; + } + +exit: + return err; +} + + +/* 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) +{ + int err = 0; + unsigned i; + unsigned max_corrected = 0; + unsigned opno = 0; + /* We don't expect more than this many correctable bit errors per + * page. */ + #define MAXBITS 512 + static unsigned bitstats[MAXBITS]; /* bit error histogram. */ + + memset(bitstats, 0, sizeof(bitstats)); + + msg("overwrite biterrors test\n"); + + for (i = 0; i < mtd->writesize; i++) + wbuffer[i] = hash(i+seed); + + err = write_page(1); + if (err) + goto exit; + + while (opno < max_overwrite) { + + err = rewrite_page(0); + if (err) + break; + + err = read_page(0); + if (err >= 0) { + if (err >= MAXBITS) { + msg("Implausible number of bit errors corrected\n"); + err = -EIO; + break; + } + bitstats[err]++; + if (err > max_corrected) { + max_corrected = err; + msg("Read reported %d corrected bit errors\n", + err); + } + } else { /* err < 0 */ + msg("Read reported error %d\n", err); + err = 0; + break; + } + + err = verify_page(0); + if (err) { + bitstats[max_corrected] = opno; + msg("ECC failure, read data is incorrect despite read success\n"); + break; + } + + opno++; + } + + /* 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. */ + msg("Bit error histogram (%d operations total):\n", opno); + for (i = 0; i < max_corrected; i++) + msg("Page reads with %3d corrected bit errors: %d\n", + i, bitstats[i]); + +exit: + return err; +} + +static int __init mtd_nandbiterrs_init(void) +{ + int err = 0; + + msg("\n"); + msg("==================================================\n"); + msg("MTD device: %d\n", dev); + + mtd = get_mtd_device(NULL, dev); + if (IS_ERR(mtd)) { + err = PTR_ERR(mtd); + msg("error: cannot get MTD device\n"); + goto exit_mtddev; + } + + if (mtd->type != MTD_NANDFLASH) { + msg("this test requires NAND flash\n"); + err = -ENODEV; + goto exit_nand; + } + + msg("MTD device size %llu, eraseblock=%u, page=%u, oob=%u\n", + (unsigned long long)mtd->size, mtd->erasesize, + mtd->writesize, mtd->oobsize); + + subsize = mtd->writesize >> mtd->subpage_sft; + subcount = mtd->writesize / subsize; + + msg("Device uses %d subpages of %d bytes\n", subcount, subsize); + + offset = page_offset * mtd->writesize; + eraseblock = mtd_div_by_eb(offset, mtd); + + msg("Using page=%u, offset=%llu, eraseblock=%u\n", + page_offset, offset, eraseblock); + + wbuffer = kmalloc(mtd->writesize, GFP_KERNEL); + if (!wbuffer) { + err = -ENOMEM; + goto exit_wbuffer; + } + + rbuffer = kmalloc(mtd->writesize, GFP_KERNEL); + if (!rbuffer) { + err = -ENOMEM; + goto exit_rbuffer; + } + + err = erase_block(); + if (err) + goto exit_error; + + if (mode == 0) + err = incremental_errors_test(); + else + err = overwrite_test(); + + if (err) + goto exit_error; + + /* We leave the block un-erased in case of test failure. */ + err = erase_block(); + if (err) + goto exit_error; + + err = -EIO; + msg("finished successfully.\n"); + msg("==================================================\n"); + +exit_error: + kfree(rbuffer); +exit_rbuffer: + kfree(wbuffer); +exit_wbuffer: + /* Nothing */ +exit_nand: + put_mtd_device(mtd); +exit_mtddev: + return err; +} + +static void __exit mtd_nandbiterrs_exit(void) +{ + return; +} + +module_init(mtd_nandbiterrs_init); +module_exit(mtd_nandbiterrs_exit); + +MODULE_DESCRIPTION("NAND bit error recovery test"); +MODULE_AUTHOR("Iwo Mergler"); +MODULE_LICENSE("GPL");

Test for multi-bit error correction

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