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)
 *
 * $Id: nand_bbt.c,v 1.31 2005/02/16 17:09:36 dedekind Exp $
 *
 * 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 * If one of the bbt's is out of date or does not exist it is (re)created.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 neccecary 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>


/** 
 * 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;

	if (td->options & NAND_BBT_SCANEMPTY) {
		end = paglen + td->offs;
		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;
}

/**
 * read_bbt - [GENERIC] Read the bad block table starting from page
 * @mtd:	MTD device structure
 * @buf:	temporary buffer
 * @page:	the starting page
 * @num:	the number of bbt descriptors to read
 * @bits:	number of bits per block
 * @offs:	offset in the memory table
 * @reserved_block_code:	Pattern to identify reserved blocks
 *
 * Read the bad block table starting from page.
 *
 */
static int read_bbt (struct mtd_info *mtd, uint8_t *buf, int page, int num, 
	int bits, int offs, int reserved_block_code)
{
	int res, i, j, act = 0;
	struct nand_chip *this = mtd->priv;
	size_t retlen, len, totlen;
	loff_t from;
	uint8_t msk = (uint8_t) ((1 << bits) - 1);

	totlen = (num * bits) >> 3;
	from = ((loff_t)page) << this->page_shift;
	
	while (totlen) {
		len = min (totlen, (size_t) (1 << this->bbt_erase_shift));
		res = mtd->read_ecc (mtd, from, len, &retlen, buf, NULL, this->autooob);
		if (res < 0) {
			if (retlen != len) {
				printk (KERN_INFO "nand_bbt: Error reading bad block table\n");
				return res;
			}
			printk (KERN_WARNING "nand_bbt: ECC error while reading bad block table\n");
		}	

		/* Analyse data */
		for (i = 0; i < len