/*
* 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.
*
*
* 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 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/nand.h>
#include <linux/slab.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;
}
static int erase_block(void)
{
int err;
struct erase_info ei;
loff_t addr = eraseblock * mtd->erasesize;
pr_info("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) {
pr_err("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)
pr_info("write_page\n");
err = mtd_write(mtd, offset, mtd->writesize, &written, wbuffer);
if (err || written != mtd->writesize) {
pr_err("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)
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 == -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 = rewrite_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;
}
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 != MTD_NANDFLASH) {
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 = 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 = 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;
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");