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 no flash based BBT
 * (NAND_BBT_USE_FLASH) is specified then the device is scanned for factory
 * marked good / bad blocks. This information is used to create a memory BBT.
 * Once a new bad block is discovered then the "factory" information is updated
 * on the device.
 * If a flash based BBT is specified then the function first tries to find the
 * BBT on flash. 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 * If one of the BBTs is out of date or does not exist it is (re)created.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 auto generated 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. If the NAND
 * controller needs the complete OOB area for the ECC information then the
 * option NAND_BBT_NO_OOB should be used (along with NAND_BBT_USE_FLASH, of
 * course): it moves the ident pattern and the version byte into the data area
 * and the OOB area will remain untouched.
 *
 * 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/bitops.h>
#include <linux/delay.h>
#include <linux/vmalloc.h>
#include <linux/export.h>

static int check_pattern_no_oob(uint8_t *buf, struct nand_bbt_descr *td)
{
	int ret;

	ret = memcmp(buf, td->pattern, td->len);
	if (!ret)
		return ret;
	return -1;
}

/**
 * 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 pag