nand_bbt.c

老版本的mtd-snap

/*
 *  drivers/mtd/nand_bbt.c
 *
 *  Overview:
 *   Bad block table support for the NAND driver
 *   
 *  Copyright (C) 2004 Thomas Gleixner ([e-mail])
 *
 * $Id: nand_bbt.c,v 1.35 2005/07/15 13:53:47 gleixner 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 * If one of the bbt's is out of date or does not exist it is (re)created.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;

	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 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; i++) {
			uint8_t dat = buf[i];
			for (j = 0; j < 8; j += bits, act += 2) {
				uint8_t tmp = (dat >> j) & msk;
				if (tmp == msk)
					continue;
				if (reserved_block_code &&
				    (tmp == reserved_block_code)) {
					printk (KERN_DEBUG "nand_read_bbt: Reserved block at 0x%08x\n",
						((offs << 2) + (act >> 1)) << this->bbt_erase_shift);
					this->bbt[offs + (act >> 3)] |= 0x2 << (act & 0x06);
					continue;
				}
				/* Leave it for now, if its matured we can move this
				 * message to MTD_DEBUG_LEVEL0 */
				printk (KERN_DEBUG "nand_read_bbt: Bad block at 0x%08x\n",
					((offs << 2) + (act >> 1)) << this->bbt_erase_shift);
				/* Factory marked bad or worn out ? */	
				if (tmp == 0)
					this->bbt[offs + (act >> 3)] |= 0x3 << (act & 0x06);
				else
					this->bbt[offs + (act >> 3)] |= 0x1 << (act & 0x06);
			}	
		}
		totlen -= len;
		from += len;
	}
	return 0;
}

/**
 * read_abs_bbt - [GENERIC] Read the bad block table starting at a given page
 * @mtd:	MTD device structure
 * @buf:	temporary buffer
 * @td:		descriptor for the bad block table 
 * @chip:	read the table for a specific chip, -1 read all chips.
 *		Applies only if NAND_BBT_PERCHIP option is set
 *
 * Read the bad block table for all chips starting at a given page
 * We assume that the bbt bits are in consecutive order.
*/
static int read_abs_bbt (struct mtd_info *mtd, uint8_t *buf, struct nand_bbt_descr *td, int chip)
{
	struct nand_chip *this = mtd->priv;
	int res = 0, i;
	int bits;

	bits = td->options & NAND_BBT_NRBITS_MSK;
	if (td->options & NAND_BBT_PERCHIP) {
		int offs = 0;
		for (i = 0; i < this->numchips; i++) {
			if (chip == -1 || chip == i)
				res = read_bbt (mtd, buf, td->pages[i], this->chipsize >> this->bbt_erase_shift, bits, offs, td->reserved_block_code);
			if (res)
				return res;
			offs += this->chipsize >> (this->bbt_erase_shift + 2);
		}
	} else {
		res = read_bbt (mtd, buf, td->pages[0], mtd->size >> this->bbt_erase_shift, bits, 0, td->reserved_block_code);
		if (res)
			return res;
	}
	return 0;
}

/**
 * read_abs_bbts - [GENERIC] Read the bad block table(s) for all chips starting at a given page
 * @mtd:	MTD device structure
 * @buf:	temporary buffer
 * @td:		descriptor for the bad block table 
 * @md:		descriptor for the bad block table mirror
 *
 * Read the bad block table(s) for all chips starting at a given page
 * We assume that the bbt bits are in consecutive order.
 *
*/
static int read_abs_bbts (struct mtd_info *mtd, uint8_t *buf, struct nand_bbt_descr *td,
	struct nand_bbt_descr *md)
{
	struct nand_chip *this = mtd->priv;

	/* Read the primary version, if available */	
	if (td->options & NAND_BBT_VERSION) {
		nand_read_raw (mtd, buf, td->pages[0] << this->page_shift, mtd->oobblock, mtd->oobsize); 
		td->version[0] = buf[mtd->oobblock + td->veroffs];
		printk (KERN_DEBUG "Bad block table at page %d, version 0x%02X\n", td->pages[0], td->version[0]);
	}

	/* Read the mirror version, if available */	
	if (md && (md->options & NAND_BBT_VERSION)) {
		nand_read_raw (mtd, buf, md->pages[0] << this->page_shift, mtd->oobblock, mtd->oobsize); 
		md->version[0] = buf[mtd->oobblock + md->veroffs];
		printk (KERN_DEBUG "Bad block table at page %d, version 0x%02X\n", md->pages[0], md->version[0]);
	}

	return 1;
}

/**
 * create_bbt - [GENERIC] Create a bad block table by scanning the device
 * @mtd:	MTD device structure
 * @buf:	temporary buffer
 * @bd:		descriptor for the good/bad block search pattern
 * @chip:	create the table for a specific chip, -1 read all chips.
 *		Applies only if NAND_BBT_PERCHIP option is set
 *
 * Create a bad block table by scanning the device
 * for the given good/bad block identify pattern
 */
static int create_bbt (struct mtd_info *mtd, uint8_t *buf, struct nand_bbt_descr *bd, int chip)
{
	struct nand_chip *this = mtd->priv;
	int i, j, numblocks, len, scanlen;
	int startblock;
	loff_t from;
	size_t readlen, ooblen;

	printk (KERN_INFO "Scanning device for bad blocks\n");

	if (bd->options & NAND_BBT_SCANALLPAGES)
		len = 1 << (this->bbt_erase_shift - this->page_shift);
	else {
		if (bd->options & NAND_BBT_SCAN2NDPAGE)
			len = 2;
		else	
			len = 1;
	}

	if (!(bd->options & NAND_BBT_SCANEMPTY)) {
		/* We need only read few bytes from the OOB area */
		scanlen = ooblen = 0;
		readlen = bd->len;
	} else {
		/* Full page content should be read */
		scanlen	= mtd->oobblock + mtd->oobsize;
		readlen = len * mtd->oobblock;
		ooblen = len * mtd->oobsize;
	}

	if (chip == -1) {
		/* Note that numblocks is 2 * (real numblocks) here, see i+=2 below as it
		 * makes shifting and masking less painful */
		numblocks = mtd->size >> (this->bbt_erase_shift - 1);
		startblock = 0;
		from = 0;
	} else {
		if (chip >= this->numchips) {
			printk (KERN_WARNING "create_bbt(): chipnr (%d) > available chips (%d)\n",
				chip + 1, this->numchips);
			return -EINVAL;
		}
		numblocks = this->chipsize >> (this->bbt_erase_shift - 1);
		startblock = chip * numblocks;
		numblocks += startblock;
		from = startblock << (this->bbt_erase_shift - 1);
	}
	
	for (i = startblock; i < numblocks;) {
		int ret;
		
		if (bd->options & NAND_BBT_SCANEMPTY)
			if ((ret = nand_read_raw (mtd, buf, from, readlen, ooblen)))
				return ret;

		for (j = 0; j < len; j++) {
			if (!(bd->options & NAND_BBT_SCANEMPTY)) {
				size_t retlen;
				
				/* Read the full oob until read_oob is fixed to 
				 * handle single byte reads for 16 bit buswidth */
				ret = mtd->read_oob(mtd, from + j * mtd->oobblock,
							mtd->oobsize, &retlen, buf);
				if (ret)
					return ret;

				if (check_short_pattern (buf, bd)) {
					this->bbt[i >> 3] |= 0x03 << (i & 0x6);
					printk (KERN_WARNING "Bad eraseblock %d at 0x%08x\n", 
						i >> 1, (unsigned int) from);
					break;
				}
			} else {
				if (check_pattern (&buf[j * scanlen], scanlen, mtd->oobblock, bd)) {
					this->bbt[i >> 3] |= 0x03 << (i & 0x6);
					printk (KERN_WARNING "Bad eraseblock %d at 0x%08x\n", 
						i >> 1, (unsigned int) from);
					break;
				}
			}
		}
		i += 2;
		from += (1 << this->bbt_erase_shift);
	}
	return 0;
}

/**
 * search_bbt - [GENERIC] scan the device for a specific bad block table
 * @mtd:	MTD device structure
 * @buf:	temporary buffer
 * @td:		descriptor for the bad block table
 *
 * Read the bad block table by searching for a given ident pattern.