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Diffstat (limited to '')
| -rw-r--r-- | drivers/mtd/tests/nandbiterrs.c | 419 |
1 files changed, 419 insertions, 0 deletions
diff --git a/drivers/mtd/tests/nandbiterrs.c b/drivers/mtd/tests/nandbiterrs.c new file mode 100644 index 000000000..98d7508f9 --- /dev/null +++ b/drivers/mtd/tests/nandbiterrs.c @@ -0,0 +1,419 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright © 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. + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/init.h> +#include <linux/module.h> +#include <linux/moduleparam.h> +#include <linux/mtd/mtd.h> +#include <linux/err.h> +#include <linux/mtd/rawnand.h> +#include <linux/slab.h> +#include "mtd_test.h" + +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; +} + +/* Writes wbuffer to page */ +static int write_page(int log) +{ + if (log) + pr_info("write_page\n"); + + return mtdtest_write(mtd, offset, mtd->writesize, wbuffer); +} + +/* 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) + pr_info("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) { + pr_err("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) + pr_info("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 || err == -EUCLEAN) + err = mtd->ecc_stats.corrected - oldstats.corrected; + + if (err < 0 || read != mtd->writesize) { + pr_err("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) + pr_info("verify_page\n"); + + for (i = 0; i < mtd->writesize; i++) { + if (rbuffer[i] != hash(i+seed)) { + pr_err("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); + pr_info("Inserted biterror @ %u/%u\n", byte, bit); + return 0; + } + } + byte++; + } + pr_err("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; + + pr_info("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) + pr_info("Read reported %d corrected bit errors\n", err); + if (err < 0) { + pr_err("After %d biterrors per subpage, read reported error %d\n", + errs_per_subpage, err); + err = 0; + goto exit; + } + + err = verify_page(1); + if (err) { + pr_err("ECC failure, read data is incorrect despite read success\n"); + goto exit; + } + + pr_info("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)); + + pr_info("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 = write_page(0); + if (err) + break; + + err = read_page(0); + if (err >= 0) { + if (err >= MAXBITS) { + pr_info("Implausible number of bit errors corrected\n"); + err = -EIO; + break; + } + bitstats[err]++; + if (err > max_corrected) { + max_corrected = err; + pr_info("Read reported %d corrected bit errors\n", + err); + } + } else { /* err < 0 */ + pr_info("Read reported error %d\n", err); + err = 0; + break; + } + + err = verify_page(0); + if (err) { + bitstats[max_corrected] = opno; + pr_info("ECC failure, read data is incorrect despite read success\n"); + break; + } + + err = mtdtest_relax(); + if (err) + 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. */ + pr_info("Bit error histogram (%d operations total):\n", opno); + for (i = 0; i < max_corrected; i++) + pr_info("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; + + printk("\n"); + printk(KERN_INFO "==================================================\n"); + pr_info("MTD device: %d\n", dev); + + mtd = get_mtd_device(NULL, dev); + if (IS_ERR(mtd)) { + err = PTR_ERR(mtd); + pr_err("error: cannot get MTD device\n"); + goto exit_mtddev; + } + + if (!mtd_type_is_nand(mtd)) { + pr_info("this test requires NAND flash\n"); + err = -ENODEV; + goto exit_nand; + } + + pr_info("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; + + pr_info("Device uses %d subpages of %d bytes\n", subcount, subsize); + + offset = (loff_t)page_offset * mtd->writesize; + eraseblock = mtd_div_by_eb(offset, mtd); + + pr_info("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 = mtdtest_erase_eraseblock(mtd, eraseblock); + 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 = mtdtest_erase_eraseblock(mtd, eraseblock); + if (err) + goto exit_error; + + err = -EIO; + pr_info("finished successfully.\n"); + printk(KERN_INFO "==================================================\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"); |