path: root/drivers/mtd/nand/nand_bbt.c

/*
 *  drivers/mtd/nand_bbt.c
 *
 *  Overview:
 *   Bad block table support for the NAND driver
 *
 *  Copyright (C) 2004 Thomas Gleixner (tglx@linutronix.de)
 *
 * 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.
 *
 * Description:
 *
 * When nand_scan_bbt is called, then it tries to find the bad block table
 * depending on the options in the bbt descriptor(s). If a bbt is found
 * then the contents are read and the memory based bbt is created. If a
 * mirrored bbt is selected then the mirror is searched too and the
 * versions are compared. If the mirror has a greater version number
 * than the mirror bbt is used to build the memory based bbt.
 * If the tables are not versioned, then we "or" the bad block information.
 * If one of the bbt's is out of date or does not exist it is (re)created.
 * If no bbt exists at all then the device is scanned for factory marked
 * good / bad blocks and the bad block tables are created.
 *
 * For manufacturer created bbts like the one found on M-SYS DOC devices
 * the bbt is searched and read but never created
 *
 * The autogenerated bad block table is located in the last good blocks
 * of the device. The table is mirrored, so it can be updated eventually.
 * The table is marked in the oob area with an ident pattern and a version
 * number which indicates which of both tables is more up to date.
 *
 * The table uses 2 bits per block
 * 11b: 	block is good
 * 00b: 	block is factory marked bad
 * 01b, 10b: 	block is marked bad due to wear
 *
 * The memory bad block table uses the following scheme:
 * 00b:		block is good
 * 01b:		block is marked bad due to wear
 * 10b:		block is reserved (to protect the bbt area)
 * 11b:		block is factory marked bad
 *
 * Multichip devices like DOC store the bad block info per floor.
 *
 * Following assumptions are made:
 * - bbts start at a page boundary, if autolocated on a block boundary
 * - the space necessary for a bbt in FLASH does not exceed a block boundary
 *
 */

#include <linux/slab.h>
#include <linux/types.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/nand.h>
#include <linux/mtd/nand_ecc.h>
#include <linux/mtd/compatmac.h>
#include <linux/bitops.h>
#include <linux/delay.h>
#include <linux/vmalloc.h>

/**
 * check_pattern - [GENERIC] check if a pattern is in the buffer
 * @buf:	the buffer to search
 * @len:	the length of buffer to search
 * @paglen:	the pagelength
 * @td:		search pattern descriptor
 *
 * Check for a pattern at the given place. Used to search bad block
 * tables and good / bad block identifiers.
 * If the SCAN_EMPTY option is set then check, if all bytes except the
 * pattern area contain 0xff
 *
*/
static int check_pattern(uint8_t *buf, int len, int paglen, struct nand_bbt_descr *td)
{
	int i, end = 0;
	uint8_t *p = buf;

	end = paglen + td->offs;
	if (td->options & NAND_BBT_SCANEMPTY) {
		for (i = 0; i < end; i++) {
			if (p[i] != 0xff)
				return -1;
		}
	}
	p += end;

	/* Compare the pattern */
	for (i = 0; i < td->len; i++) {
		if (p[i] != td->pattern[i])
			return -1;
	}

	if (td->options & NAND_BBT_SCANEMPTY) {
		p += td->len;
		end += td->len;
		for (i = end; i < len; i++) {
			if (*p++ != 0xff)
				return -1;
		}
	}
	return 0;
}

/**
 * check_short_pattern - [GENERIC] check if a pattern is in the buffer
 * @buf:	the buffer to search
 * @td:		search pattern descriptor
 *
 * Check for a pattern at the given place. Used to search bad block
 * tables and good / bad block identifiers. Same as check_pattern, but
 * no optional empty check
 *
*/
static int check_short_pattern(uint8_t *buf, struct nand_bbt_descr *td)
{
	int i;
	uint8_t *p = buf;

	/* Compare the pattern */
	for (i = 0; i < td->len; i++) {
		if (p[td->offs + i] != td->pattern[i])
			return -1;
	}
	return 0;
}

/**
 * read_bbt - [GENERIC] Read the bad block table starting from page
 * @mtd:	MTD device structure
 * @buf:	temporary buffer
 * @page:	the startin