433 lines
10 KiB
C
433 lines
10 KiB
C
/*
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* Copyright © 2012 NetCommWireless
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* Iwo Mergler <Iwo.Mergler@netcommwireless.com.au>
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*
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* Test for multi-bit error recovery on a NAND page This mostly tests the
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* ECC controller / driver.
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*
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* There are two test modes:
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*
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* 0 - artificially inserting bit errors until the ECC fails
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* This is the default method and fairly quick. It should
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* be independent of the quality of the FLASH.
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*
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* 1 - re-writing the same pattern repeatedly until the ECC fails.
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* This method relies on the physics of NAND FLASH to eventually
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* generate '0' bits if '1' has been written sufficient times.
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* Depending on the NAND, the first bit errors will appear after
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* 1000 or more writes and then will usually snowball, reaching the
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* limits of the ECC quickly.
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*
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* The test stops after 10000 cycles, should your FLASH be
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* exceptionally good and not generate bit errors before that. Try
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* a different page in that case.
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*
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* Please note that neither of these tests will significantly 'use up' any
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* FLASH endurance. Only a maximum of two erase operations will be performed.
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*
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as published by
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* the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; see the file COPYING. If not, write to the Free Software
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* Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/moduleparam.h>
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#include <linux/mtd/mtd.h>
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#include <linux/err.h>
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#include <linux/mtd/nand.h>
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#include <linux/slab.h>
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#include "mtd_test.h"
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static int dev;
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module_param(dev, int, S_IRUGO);
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MODULE_PARM_DESC(dev, "MTD device number to use");
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static unsigned page_offset;
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module_param(page_offset, uint, S_IRUGO);
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MODULE_PARM_DESC(page_offset, "Page number relative to dev start");
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static unsigned seed;
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module_param(seed, uint, S_IRUGO);
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MODULE_PARM_DESC(seed, "Random seed");
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static int mode;
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module_param(mode, int, S_IRUGO);
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MODULE_PARM_DESC(mode, "0=incremental errors, 1=overwrite test");
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static unsigned max_overwrite = 10000;
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static loff_t offset; /* Offset of the page we're using. */
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static unsigned eraseblock; /* Eraseblock number for our page. */
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/* We assume that the ECC can correct up to a certain number
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* of biterrors per subpage. */
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static unsigned subsize; /* Size of subpages */
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static unsigned subcount; /* Number of subpages per page */
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static struct mtd_info *mtd; /* MTD device */
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static uint8_t *wbuffer; /* One page write / compare buffer */
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static uint8_t *rbuffer; /* One page read buffer */
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/* 'random' bytes from known offsets */
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static uint8_t hash(unsigned offset)
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{
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unsigned v = offset;
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unsigned char c;
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v ^= 0x7f7edfd3;
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v = v ^ (v >> 3);
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v = v ^ (v >> 5);
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v = v ^ (v >> 13);
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c = v & 0xFF;
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/* Reverse bits of result. */
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c = (c & 0x0F) << 4 | (c & 0xF0) >> 4;
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c = (c & 0x33) << 2 | (c & 0xCC) >> 2;
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c = (c & 0x55) << 1 | (c & 0xAA) >> 1;
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return c;
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}
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/* Writes wbuffer to page */
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static int write_page(int log)
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{
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if (log)
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pr_info("write_page\n");
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return mtdtest_write(mtd, offset, mtd->writesize, wbuffer);
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}
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/* Re-writes the data area while leaving the OOB alone. */
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static int rewrite_page(int log)
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{
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int err = 0;
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struct mtd_oob_ops ops;
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if (log)
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pr_info("rewrite page\n");
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ops.mode = MTD_OPS_RAW; /* No ECC */
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ops.len = mtd->writesize;
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ops.retlen = 0;
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ops.ooblen = 0;
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ops.oobretlen = 0;
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ops.ooboffs = 0;
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ops.datbuf = wbuffer;
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ops.oobbuf = NULL;
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err = mtd_write_oob(mtd, offset, &ops);
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if (err || ops.retlen != mtd->writesize) {
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pr_err("error: write_oob failed (%d)\n", err);
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if (!err)
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err = -EIO;
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}
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return err;
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}
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/* Reads page into rbuffer. Returns number of corrected bit errors (>=0)
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* or error (<0) */
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static int read_page(int log)
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{
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int err = 0;
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size_t read;
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struct mtd_ecc_stats oldstats;
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if (log)
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pr_info("read_page\n");
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/* Saving last mtd stats */
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memcpy(&oldstats, &mtd->ecc_stats, sizeof(oldstats));
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err = mtd_read(mtd, offset, mtd->writesize, &read, rbuffer);
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if (err == -EUCLEAN)
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err = mtd->ecc_stats.corrected - oldstats.corrected;
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if (err < 0 || read != mtd->writesize) {
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pr_err("error: read failed at %#llx\n", (long long)offset);
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if (err >= 0)
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err = -EIO;
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}
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return err;
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}
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/* Verifies rbuffer against random sequence */
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static int verify_page(int log)
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{
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unsigned i, errs = 0;
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if (log)
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pr_info("verify_page\n");
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for (i = 0; i < mtd->writesize; i++) {
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if (rbuffer[i] != hash(i+seed)) {
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pr_err("Error: page offset %u, expected %02x, got %02x\n",
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i, hash(i+seed), rbuffer[i]);
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errs++;
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}
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}
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if (errs)
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return -EIO;
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else
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return 0;
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}
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#define CBIT(v, n) ((v) & (1 << (n)))
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#define BCLR(v, n) ((v) = (v) & ~(1 << (n)))
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/* Finds the first '1' bit in wbuffer starting at offset 'byte'
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* and sets it to '0'. */
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static int insert_biterror(unsigned byte)
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{
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int bit;
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while (byte < mtd->writesize) {
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for (bit = 7; bit >= 0; bit--) {
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if (CBIT(wbuffer[byte], bit)) {
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BCLR(wbuffer[byte], bit);
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pr_info("Inserted biterror @ %u/%u\n", byte, bit);
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return 0;
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}
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}
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byte++;
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}
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pr_err("biterror: Failed to find a '1' bit\n");
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return -EIO;
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}
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/* Writes 'random' data to page and then introduces deliberate bit
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* errors into the page, while verifying each step. */
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static int incremental_errors_test(void)
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{
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int err = 0;
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unsigned i;
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unsigned errs_per_subpage = 0;
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pr_info("incremental biterrors test\n");
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for (i = 0; i < mtd->writesize; i++)
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wbuffer[i] = hash(i+seed);
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err = write_page(1);
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if (err)
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goto exit;
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while (1) {
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err = rewrite_page(1);
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if (err)
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goto exit;
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err = read_page(1);
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if (err > 0)
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pr_info("Read reported %d corrected bit errors\n", err);
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if (err < 0) {
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pr_err("After %d biterrors per subpage, read reported error %d\n",
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errs_per_subpage, err);
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err = 0;
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goto exit;
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}
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err = verify_page(1);
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if (err) {
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pr_err("ECC failure, read data is incorrect despite read success\n");
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goto exit;
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}
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pr_info("Successfully corrected %d bit errors per subpage\n",
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errs_per_subpage);
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for (i = 0; i < subcount; i++) {
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err = insert_biterror(i * subsize);
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if (err < 0)
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goto exit;
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}
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errs_per_subpage++;
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}
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exit:
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return err;
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}
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/* Writes 'random' data to page and then re-writes that same data repeatedly.
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This eventually develops bit errors (bits written as '1' will slowly become
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'0'), which are corrected as far as the ECC is capable of. */
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static int overwrite_test(void)
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{
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int err = 0;
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unsigned i;
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unsigned max_corrected = 0;
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unsigned opno = 0;
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/* We don't expect more than this many correctable bit errors per
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* page. */
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#define MAXBITS 512
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static unsigned bitstats[MAXBITS]; /* bit error histogram. */
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memset(bitstats, 0, sizeof(bitstats));
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pr_info("overwrite biterrors test\n");
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for (i = 0; i < mtd->writesize; i++)
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wbuffer[i] = hash(i+seed);
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err = write_page(1);
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if (err)
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goto exit;
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while (opno < max_overwrite) {
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err = rewrite_page(0);
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if (err)
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break;
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err = read_page(0);
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if (err >= 0) {
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if (err >= MAXBITS) {
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pr_info("Implausible number of bit errors corrected\n");
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err = -EIO;
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break;
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}
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bitstats[err]++;
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if (err > max_corrected) {
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max_corrected = err;
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pr_info("Read reported %d corrected bit errors\n",
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err);
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}
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} else { /* err < 0 */
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pr_info("Read reported error %d\n", err);
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err = 0;
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break;
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}
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err = verify_page(0);
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if (err) {
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bitstats[max_corrected] = opno;
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pr_info("ECC failure, read data is incorrect despite read success\n");
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break;
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}
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err = mtdtest_relax();
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if (err)
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break;
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opno++;
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}
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/* At this point bitstats[0] contains the number of ops with no bit
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* errors, bitstats[1] the number of ops with 1 bit error, etc. */
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pr_info("Bit error histogram (%d operations total):\n", opno);
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for (i = 0; i < max_corrected; i++)
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pr_info("Page reads with %3d corrected bit errors: %d\n",
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i, bitstats[i]);
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exit:
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return err;
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}
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static int __init mtd_nandbiterrs_init(void)
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{
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int err = 0;
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printk("\n");
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printk(KERN_INFO "==================================================\n");
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pr_info("MTD device: %d\n", dev);
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mtd = get_mtd_device(NULL, dev);
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if (IS_ERR(mtd)) {
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err = PTR_ERR(mtd);
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pr_err("error: cannot get MTD device\n");
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goto exit_mtddev;
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}
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if (!mtd_type_is_nand(mtd)) {
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pr_info("this test requires NAND flash\n");
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err = -ENODEV;
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goto exit_nand;
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}
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pr_info("MTD device size %llu, eraseblock=%u, page=%u, oob=%u\n",
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(unsigned long long)mtd->size, mtd->erasesize,
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mtd->writesize, mtd->oobsize);
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subsize = mtd->writesize >> mtd->subpage_sft;
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subcount = mtd->writesize / subsize;
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pr_info("Device uses %d subpages of %d bytes\n", subcount, subsize);
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offset = (loff_t)page_offset * mtd->writesize;
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eraseblock = mtd_div_by_eb(offset, mtd);
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pr_info("Using page=%u, offset=%llu, eraseblock=%u\n",
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page_offset, offset, eraseblock);
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wbuffer = kmalloc(mtd->writesize, GFP_KERNEL);
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if (!wbuffer) {
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err = -ENOMEM;
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goto exit_wbuffer;
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}
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rbuffer = kmalloc(mtd->writesize, GFP_KERNEL);
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if (!rbuffer) {
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err = -ENOMEM;
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goto exit_rbuffer;
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}
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err = mtdtest_erase_eraseblock(mtd, eraseblock);
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if (err)
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goto exit_error;
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if (mode == 0)
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err = incremental_errors_test();
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else
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err = overwrite_test();
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if (err)
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goto exit_error;
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/* We leave the block un-erased in case of test failure. */
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err = mtdtest_erase_eraseblock(mtd, eraseblock);
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if (err)
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goto exit_error;
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err = -EIO;
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pr_info("finished successfully.\n");
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printk(KERN_INFO "==================================================\n");
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exit_error:
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kfree(rbuffer);
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exit_rbuffer:
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kfree(wbuffer);
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exit_wbuffer:
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/* Nothing */
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exit_nand:
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put_mtd_device(mtd);
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exit_mtddev:
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return err;
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}
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static void __exit mtd_nandbiterrs_exit(void)
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{
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return;
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}
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module_init(mtd_nandbiterrs_init);
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module_exit(mtd_nandbiterrs_exit);
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MODULE_DESCRIPTION("NAND bit error recovery test");
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MODULE_AUTHOR("Iwo Mergler");
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MODULE_LICENSE("GPL");
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