1 files changed, 1056 insertions, 0 deletions

diff --git a/drivers/mtd/nand/nand_bbt.c b/drivers/mtd/nand/nand_bbt.c
new file mode 100644
index 000000000000..9a1949751c1f
--- /dev/null
+++ b/drivers/mtd/nand/nand_bbt.c
@@ -0,0 +1,1056 @@
+/*
+ *  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 1.28 2004/11/13 10:19:09 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+ * If one of the bbt's is out of date or does not exist it is (re)created.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;
+        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;
+        }
+
+        p += td->len;
+        end += td->len;
+        if (td->options & NAND_BBT_SCANEMPTY) {
+                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; 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 void 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;
+        }
+        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; 
+                }
+                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;) {
+                nand_read_raw (mtd, buf, from, readlen, ooblen);
+                for (j = 0; j < len; j++) {
+                        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);
+        }
+}
+
+/**
+ * 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.
+ * Search is preformed either from the beginning up or from the end of 
+ * the device downwards. The search starts always at the start of a
+ * block.
+ * If the option NAND_BBT_PERCHIP is given, each chip is searched 
+ * for a bbt, which contains the bad block information of this chip.
+ * This is neccecary to provide support for certain DOC devices.
+ *
+ * The bbt ident pattern resides in the oob area of the first page 
+ * in a block. 
+ */
+static int search_bbt (struct mtd_info *mtd, uint8_t *buf, struct nand_bbt_descr *td)
+{
+        struct nand_chip *this = mtd->priv;
+        int i, chips;
+        int bits, startblock, block, dir;
+        int scanlen = mtd->oobblock + mtd->oobsize;
+        int bbtblocks;
+
+        /* Search direction top -> down ? */
+        if (td->options & NAND_BBT_LASTBLOCK) {
+                startblock = (mtd->size >> this->bbt_erase_shift) -1;
+                dir = -1;
+        } else {
+                startblock = 0; 
+                dir = 1;
+        }       
+        
+        /* Do we have a bbt per chip ? */
+        if (td->options & NAND_BBT_PERCHIP) {
+                chips = this->numchips;
+                bbtblocks = this->chipsize >> this->bbt_erase_shift;
+                startblock &= bbtblocks - 1;
+        } else {
+                chips = 1;
+                bbtblocks = mtd->size >> this->bbt_erase_shift;
+        }
+        
+        /* Number of bits for each erase block in the bbt */
+        bits = td->options & NAND_BBT_NRBITS_MSK;
+        
+        for (i = 0; i < chips; i++) {
+                /* Reset version information */
+                td->version[i] = 0;     
+                td->pages[i] = -1;
+                /* Scan the maximum number of blocks */
+                for (block = 0; block < td->maxblocks; block++) {
+                        int actblock = startblock + dir * block;
+                        /* Read first page */
+                        nand_read_raw (mtd, buf, actblock << this->bbt_erase_shift, mtd->oobblock, mtd->oobsize); 
+                        if (!check_pattern(buf, scanlen, mtd->oobblock, td)) {
+                                td->pages[i] = actblock << (this->bbt_erase_shift - this->page_shift);
+                                if (td->options & NAND_BBT_VERSION) {
+                                        td->version[i] = buf[mtd->oobblock + td->veroffs];
+                                }
+                                break;
+                        }
+                }
+                startblock += this->chipsize >> this->bbt_erase_shift;
+        }
+        /* Check, if we found a bbt for each requested chip */
+        for (i = 0; i < chips; i++) {
+                if (td->pages[i] == -1)
+                        printk (KERN_WARNING "Bad block table not found for chip %d\n", i);
+                else
+                        printk (KERN_DEBUG "Bad block table found at page %d, version 0x%02X\n", td->pages[i], td->version[i]);
+        }
+        return 0;       
+}
+
+/**
+ * search_read_bbts - [GENERIC] scan the device for bad block table(s)
+ * @mtd:        MTD device structure
+ * @buf:        temporary buffer
+ * @td:         descriptor for the bad block table 
+ * @md:         descriptor for the bad block table mirror
+ *
+ * Search and read the bad block table(s)
+*/
+static int search_read_bbts (struct mtd_info *mtd, uint8_t *buf, 
+        struct nand_bbt_descr *td, struct nand_bbt_descr *md)
+{
+        /* Search the primary table */
+        search_bbt (mtd, buf, td);
+                
+        /* Search the mirror table */
+        if (md)
+                search_bbt (mtd, buf, md);
+        
+        /* Force result check */
+        return 1;       
+}
+        
+
+/** 
+ * write_bbt - [GENERIC] (Re)write the bad block table
+ *
+ * @mtd:        MTD device structure
+ * @buf:        temporary buffer
+ * @td:         descriptor for the bad block table 
+ * @md:         descriptor for the bad block table mirror
+ * @chipsel:    selector for a specific chip, -1 for all
+ *
+ * (Re)write the bad block table
+ *
+*/
+static int write_bbt (struct mtd_info *mtd, uint8_t *buf, 
+        struct nand_bbt_descr *td, struct nand_bbt_descr *md, int chipsel)
+{
+        struct nand_chip *this = mtd->priv;
+        struct nand_oobinfo oobinfo;
+        struct erase_info einfo;
+        int i, j, res, chip = 0;
+        int bits, startblock, dir, page, offs, numblocks, sft, sftmsk;
+        int nrchips, bbtoffs, pageoffs;
+        uint8_t msk[4];
+        uint8_t rcode = td->reserved_block_code;
+        size_t retlen, len = 0;
+        loff_t to;
+
+        if (!rcode)
+                rcode = 0xff;
+        /* Write bad block table per chip rather than per device ? */
+        if (td->options & NAND_BBT_PERCHIP) {
+                numblocks = (int) (this->chipsize >> this->bbt_erase_shift);
+                /* Full device write or specific chip ? */      
+                if (chipsel == -1) {
+                        nrchips = this->numchips;
+                } else {
+                        nrchips = chipsel + 1;
+                        chip = chipsel;
+                }
+        } else {
+                numblocks = (int) (mtd->size >> this->bbt_erase_shift);
+                nrchips = 1;
+        }       
+        
+        /* Loop through the chips */
+        for (; chip < nrchips; chip++) {
+                
+                /* There was already a version of the table, reuse the page 
+                 * This applies for absolute placement too, as we have the 
+                 * page nr. in td->pages.
+                 */
+                if (td->pages[chip] != -1) {
+                        page = td->pages[chip];
+                        goto write;
+                }       
+
+                /* Automatic placement of the bad block table */
+                /* Search direction top -> down ? */
+                if (td->options & NAND_BBT_LASTBLOCK) {
+                        startblock = numblocks * (chip + 1) - 1;
+                        dir = -1;
+                } else {
+                        startblock = chip * numblocks;
+                        dir = 1;
+                }       
+
+                for (i = 0; i < td->maxblocks; i++) {
+                        int block = startblock + dir * i;
+                        /* Check, if the block is bad */
+                        switch ((this->bbt[block >> 2] >> (2 * (block & 0x03))) & 0x03) {
+                        case 0x01:
+                        case 0x03:
+                                continue;
+                        }
+                        page = block << (this->bbt_erase_shift - this->page_shift);
+                        /* Check, if the block is used by the mirror table */
+                        if (!md || md->pages[chip] != page)
+                                goto write;
+                }
+                printk (KERN_ERR "No space left to write bad block table\n");
+                return -ENOSPC;
+write:  
+
+                /* Set up shift count and masks for the flash table */
+                bits = td->options & NAND_BBT_NRBITS_MSK;
+                switch (bits) {
+                case 1: sft = 3; sftmsk = 0x07; msk[0] = 0x00; msk[1] = 0x01; msk[2] = ~rcode; msk[3] = 0x01; break;
+                case 2: sft = 2; sftmsk = 0x06; msk[0] = 0x00; msk[1] = 0x01; msk[2] = ~rcode; msk[3] = 0x03; break;
+                case 4: sft = 1; sftmsk = 0x04; msk[0] = 0x00; msk[1] = 0x0C; msk[2] = ~rcode; msk[3] = 0x0f; break;
+                case 8: sft = 0; sftmsk = 0x00; msk[0] = 0x00; msk[1] = 0x0F; msk[2] = ~rcode; msk[3] = 0xff; break;
+                default: return -EINVAL;
+                }
+                
+                bbtoffs = chip * (numblocks >> 2);
+                
+                to = ((loff_t) page) << this->page_shift;
+
+                memcpy (&oobinfo, this->autooob, sizeof(oobinfo));
+                oobinfo.useecc = MTD_NANDECC_PLACEONLY;
+                
+                /* Must we save the block contents ? */
+                if (td->options & NAND_BBT_SAVECONTENT) {
+                        /* Make it block aligned */
+                        to &= ~((loff_t) ((1 << this->bbt_erase_shift) - 1));
+                        len = 1 << this->bbt_erase_shift;
+                        res = mtd->read_ecc (mtd, to, len, &retlen, buf, &buf[len], &oobinfo);
+                        if (res < 0) {
+                                if (retlen != len) {
+                                        printk (KERN_INFO "nand_bbt: Error reading block for writing the bad block table\n");
+                                        return res;
+                                }
+                                printk (KERN_WARNING "nand_bbt: ECC error while reading block for writing bad block table\n");
+                        }
+                        /* Calc the byte offset in the buffer */
+                        pageoffs = page - (int)(to >> this->page_shift);
+                        offs = pageoffs << this->page_shift;
+                        /* Preset the bbt area with 0xff */
+                        memset (&buf[offs], 0xff, (size_t)(numblocks >> sft));
+                        /* Preset the bbt's oob area with 0xff */
+                        memset (&buf[len + pageoffs * mtd->oobsize], 0xff,
+                                ((len >> this->page_shift) - pageoffs) * mtd->oobsize);
+                        if (td->options & NAND_BBT_VERSION) {
+                                buf[len + (pageoffs * mtd->oobsize) + td->veroffs] = td->version[chip];
+                        }
+                } else {
+                        /* Calc length */
+                        len = (size_t) (numblocks >> sft);
+                        /* Make it page aligned ! */
+                        len = (len + (mtd->oobblock-1)) & ~(mtd->oobblock-1);
+                        /* Preset the buffer with 0xff */
+                        memset (buf, 0xff, len + (len >> this->page_shift) * mtd->oobsize);
+                        offs = 0;
+                        /* Pattern is located in oob area of first page */
+                        memcpy (&buf[len + td->offs], td->pattern, td->len);
+                        if (td->options & NAND_BBT_VERSION) {
+                                buf[len + td->veroffs] = td->version[chip];
+                        }
+                }
+        
+                /* walk through the memory table */
+                for (i = 0; i < numblocks; ) {
+                        uint8_t dat;
+                        dat = this->bbt[bbtoffs + (i >> 2)];
+                        for (j = 0; j < 4; j++ , i++) {
+                                int sftcnt = (i << (3 - sft)) & sftmsk;
+                                /* Do not store the reserved bbt blocks ! */
+                                buf[offs + (i >> sft)] &= ~(msk[dat & 0x03] << sftcnt);
+                                dat >>= 2;
+                        }
+                }
+                
+                memset (&einfo, 0, sizeof (einfo));
+                einfo.mtd = mtd;
+                einfo.addr = (unsigned long) to;
+                einfo.len = 1 << this->bbt_erase_shift;
+                res = nand_erase_nand (mtd, &einfo, 1);
+                if (res < 0) {
+                        printk (KERN_WARNING "nand_bbt: Error during block erase: %d\n", res);
+                        return res;
+                }
+        
+                res = mtd->write_ecc (mtd, to, len, &retlen, buf, &buf[len], &oobinfo);
+                if (res < 0) {
+                        printk (KERN_WARNING "nand_bbt: Error while writing bad block table %d\n", res);
+                        return res;
+                }
+                printk (KERN_DEBUG "Bad block table written to 0x%08x, version 0x%02X\n", 
+                        (unsigned int) to, td->version[chip]);
+        
+                /* Mark it as used */
+                td->pages[chip] = page;
+        }       
+        return 0;
+}
+
+/**
+ * nand_memory_bbt - [GENERIC] create a memory based bad block table
+ * @mtd:        MTD device structure
+ * @bd:         descriptor for the good/bad block search pattern
+ *
+ * The function creates a memory based bbt by scanning the device 
+ * for manufacturer / software marked good / bad blocks
+*/
+static int nand_memory_bbt (struct mtd_info *mtd, struct nand_bbt_descr *bd)
+{
+        struct nand_chip *this = mtd->priv;
+
+        /* Ensure that we only scan for the pattern and nothing else */
+        bd->options = 0;
+        create_bbt (mtd, this->data_buf, bd, -1);
+        return 0;
+}
+
+/**
+ * check_create - [GENERIC] create and write bbt(s) if neccecary
+ * @mtd:        MTD device structure
+ * @buf:        temporary buffer
+ * @bd:         descriptor for the good/bad block search pattern
+ *
+ * The function checks the results of the previous call to read_bbt
+ * and creates / updates the bbt(s) if neccecary
+ * Creation is neccecary if no bbt was found for the chip/device
+ * Update is neccecary if one of the tables is missing or the
+ * version nr. of one table is less than the other
+*/
+static int check_create (struct mtd_info *mtd, uint8_t *buf, struct nand_bbt_descr *bd)
+{
+        int i, chips, writeops, chipsel, res;
+        struct nand_chip *this = mtd->priv;
+        struct nand_bbt_descr *td = this->bbt_td;
+        struct nand_bbt_descr *md = this->bbt_md;
+        struct nand_bbt_descr *rd, *rd2;
+
+        /* Do we have a bbt per chip ? */
+        if (td->options & NAND_BBT_PERCHIP) 
+                chips = this->numchips;
+        else 
+                chips = 1;
+        
+        for (i = 0; i < chips; i++) {
+                writeops = 0;
+                rd = NULL;
+                rd2 = NULL;
+                /* Per chip or per device ? */
+                chipsel = (td->options & NAND_BBT_PERCHIP) ? i : -1;
+                /* Mirrored table avilable ? */
+                if (md) {
+                        if (td->pages[i] == -1 && md->pages[i] == -1) {
+                                writeops = 0x03;
+                                goto create;
+                        }
+
+                        if (td->pages[i] == -1) {
+                                rd = md;                                
+                                td->version[i] = md->version[i];
+                                writeops = 1;
+                                goto writecheck;
+                        }
+
+                        if (md->pages[i] == -1) {
+                                rd = td;
+                                md->version[i] = td->version[i];
+                                writeops = 2;
+                                goto writecheck;
+                        }
+
+                        if (td->version[i] == md->version[i]) {
+                                rd = td;
+                                if (!(td->options & NAND_BBT_VERSION))
+                                        rd2 = md;
+                                goto writecheck;
+                        }       
+
+                        if (((int8_t) (td->version[i] - md->version[i])) > 0) {
+                                rd = td;
+                                md->version[i] = td->version[i];
+                                writeops = 2;
+                        } else {
+                                rd = md;
+                                td->version[i] = md->version[i];
+                                writeops = 1;
+                        }
+
+                        goto writecheck;
+
+                } else {
+                        if (td->pages[i] == -1) {
+                                writeops = 0x01;
+                                goto create;
+                        }
+                        rd = td;
+                        goto writecheck;
+                }
+create:
+                /* Create the bad block table by scanning the device ? */
+                if (!(td->options & NAND_BBT_CREATE))
+                        continue;       
+                
+                /* Create the table in memory by scanning the chip(s) */
+                create_bbt (mtd, buf, bd, chipsel);
+                
+                td->version[i] = 1;
+                if (md)
+                        md->version[i] = 1;     
+writecheck:     
+                /* read back first ? */
+                if (rd)
+                        read_abs_bbt (mtd, buf, rd, chipsel);
+                /* If they weren't versioned, read both. */
+                if (rd2)
+                        read_abs_bbt (mtd, buf, rd2, chipsel);
+
+                /* Write the bad block table to the device ? */
+                if ((writeops & 0x01) && (td->options & NAND_BBT_WRITE)) {
+                        res = write_bbt (mtd, buf, td, md, chipsel);
+                        if (res < 0)
+                                return res;
+                }
+                
+                /* Write the mirror bad block table to the device ? */
+                if ((writeops & 0x02) && md && (md->options & NAND_BBT_WRITE)) {
+                        res = write_bbt (mtd, buf, md, td, chipsel);
+                        if (res < 0)
+                                return res;
+                }
+        }
+        return 0;       
+}
+
+/**
+ * mark_bbt_regions - [GENERIC] mark the bad block table regions 
+ * @mtd:        MTD device structure
+ * @td:         bad block table descriptor
+ *
+ * The bad block table regions are marked as "bad" to prevent
+ * accidental erasures / writes. The regions are identified by
+ * the mark 0x02.
+*/
+static void mark_bbt_region (struct mtd_info *mtd, struct nand_bbt_descr *td)
+{
+        struct nand_chip *this = mtd->priv;
+        int i, j, chips, block, nrblocks, update;
+        uint8_t oldval, newval;
+
+        /* Do we have a bbt per chip ? */
+        if (td->options & NAND_BBT_PERCHIP) {
+                chips = this->numchips;
+                nrblocks = (int)(this->chipsize >> this->bbt_erase_shift);
+        } else {
+                chips = 1;
+                nrblocks = (int)(mtd->size >> this->bbt_erase_shift);
+        }       
+        
+        for (i = 0; i < chips; i++) {
+                if ((td->options & NAND_BBT_ABSPAGE) ||
+                    !(td->options & NAND_BBT_WRITE)) {
+                        if (td->pages[i] == -1) continue;
+                        block = td->pages[i] >> (this->bbt_erase_shift - this->page_shift);
+                        block <<= 1;            
+                        oldval = this->bbt[(block >> 3)];
+                        newval = oldval | (0x2 << (block & 0x06));
+                        this->bbt[(block >> 3)] = newval;
+                        if ((oldval != newval) && td->reserved_block_code)
+                                nand_update_bbt(mtd, block << (this->bbt_erase_shift - 1));
+                        continue;
+                }
+                update = 0;
+                if (td->options & NAND_BBT_LASTBLOCK)
+                        block = ((i + 1) * nrblocks) - td->maxblocks;
+                else    
+                        block = i * nrblocks;
+                block <<= 1;    
+                for (j = 0; j < td->maxblocks; j++) {
+                        oldval = this->bbt[(block >> 3)];
+                        newval = oldval | (0x2 << (block & 0x06));
+                        this->bbt[(block >> 3)] = newval;
+                        if (oldval != newval) update = 1;
+                        block += 2;
+                }       
+                /* If we want reserved blocks to be recorded to flash, and some
+                   new ones have been marked, then we need to update the stored
+                   bbts.  This should only happen once. */
+                if (update && td->reserved_block_code)
+                        nand_update_bbt(mtd, (block - 2) << (this->bbt_erase_shift - 1));
+        }
+}
+
+/**
+ * nand_scan_bbt - [NAND Interface] scan, find, read and maybe create bad block table(s)
+ * @mtd:        MTD device structure
+ * @bd:         descriptor for the good/bad block search pattern
+ *
+ * The function checks, if a bad block table(s) is/are already 
+ * available. If not it scans the device for manufacturer
+ * marked good / bad blocks and writes the bad block table(s) to
+ * the selected place.
+ *
+ * The bad block table memory is allocated here. It must be freed
+ * by calling the nand_free_bbt function.
+ *
+*/
+int nand_scan_bbt (struct mtd_info *mtd, struct nand_bbt_descr *bd)
+{
+        struct nand_chip *this = mtd->priv;
+        int len, res = 0;
+        uint8_t *buf;
+        struct nand_bbt_descr *td = this->bbt_td;
+        struct nand_bbt_descr *md = this->bbt_md;
+
+        len = mtd->size >> (this->bbt_erase_shift + 2);
+        /* Allocate memory (2bit per block) */
+        this->bbt = kmalloc (len, GFP_KERNEL);
+        if (!this->bbt) {
+                printk (KERN_ERR "nand_scan_bbt: Out of memory\n");
+                return -ENOMEM;
+        }
+        /* Clear the memory bad block table */
+        memset (this->bbt, 0x00, len);
+
+        /* If no primary table decriptor is given, scan the device
+         * to build a memory based bad block table
+         */
+        if (!td)
+                return nand_memory_bbt(mtd, bd);
+
+        /* Allocate a temporary buffer for one eraseblock incl. oob */
+        len = (1 << this->bbt_erase_shift);
+        len += (len >> this->page_shift) * mtd->oobsize;
+        buf = kmalloc (len, GFP_KERNEL);
+        if (!buf) {
+                printk (KERN_ERR "nand_bbt: Out of memory\n");
+                kfree (this->bbt);
+                this->bbt = NULL;
+                return -ENOMEM;
+        }
+        
+        /* Is the bbt at a given page ? */
+        if (td->options & NAND_BBT_ABSPAGE) {
+                res = read_abs_bbts (mtd, buf, td, md);
+        } else {        
+                /* Search the bad block table using a pattern in oob */
+                res = search_read_bbts (mtd, buf, td, md);
+        }       
+
+        if (res) 
+                res = check_create (mtd, buf, bd);
+        
+        /* Prevent the bbt regions from erasing / writing */
+        mark_bbt_region (mtd, td);
+        if (md)
+                mark_bbt_region (mtd, md);
+        
+        kfree (buf);
+        return res;
+}
+
+
+/**
+ * nand_update_bbt - [NAND Interface] update bad block table(s) 
+ * @mtd:        MTD device structure
+ * @offs:       the offset of the newly marked block
+ *
+ * The function updates the bad block table(s)
+*/
+int nand_update_bbt (struct mtd_info *mtd, loff_t offs)
+{
+        struct nand_chip *this = mtd->priv;
+        int len, res = 0, writeops = 0;
+        int chip, chipsel;
+        uint8_t *buf;
+        struct nand_bbt_descr *td = this->bbt_td;
+        struct nand_bbt_descr *md = this->bbt_md;
+
+        if (!this->bbt || !td)
+                return -EINVAL;
+
+        len = mtd->size >> (this->bbt_erase_shift + 2);
+        /* Allocate a temporary buffer for one eraseblock incl. oob */
+        len = (1 << this->bbt_erase_shift);
+        len += (len >> this->page_shift) * mtd->oobsize;
+        buf = kmalloc (len, GFP_KERNEL);
+        if (!buf) {
+                printk (KERN_ERR "nand_update_bbt: Out of memory\n");
+                return -ENOMEM;
+        }
+        
+        writeops = md != NULL ? 0x03 : 0x01;
+
+        /* Do we have a bbt per chip ? */
+        if (td->options & NAND_BBT_PERCHIP) {
+                chip = (int) (offs >> this->chip_shift);
+                chipsel = chip;
+        } else {
+                chip = 0;
+                chipsel = -1;
+        }
+
+        td->version[chip]++;
+        if (md)
+                md->version[chip]++;    
+
+        /* Write the bad block table to the device ? */
+        if ((writeops & 0x01) && (td->options & NAND_BBT_WRITE)) {
+                res = write_bbt (mtd, buf, td, md, chipsel);
+                if (res < 0)
+                        goto out;
+        }
+        /* Write the mirror bad block table to the device ? */
+        if ((writeops & 0x02) && md && (md->options & NAND_BBT_WRITE)) {
+                res = write_bbt (mtd, buf, md, td, chipsel);
+        }
+
+out:    
+        kfree (buf);
+        return res;
+}
+
+/* Define some generic bad / good block scan pattern which are used 
+ * while scanning a device for factory marked good / bad blocks
+ * 
+ * The memory based patterns just 
+ */
+static uint8_t scan_ff_pattern[] = { 0xff, 0xff };
+
+static struct nand_bbt_descr smallpage_memorybased = {
+        .options = 0,
+        .offs = 5,
+        .len = 1,
+        .pattern = scan_ff_pattern
+};
+
+static struct nand_bbt_descr largepage_memorybased = {
+        .options = 0,
+        .offs = 0,
+        .len = 2,
+        .pattern = scan_ff_pattern
+};
+
+static struct nand_bbt_descr smallpage_flashbased = {
+        .options = NAND_BBT_SCANEMPTY | NAND_BBT_SCANALLPAGES,
+        .offs = 5,
+        .len = 1,
+        .pattern = scan_ff_pattern
+};
+
+static struct nand_bbt_descr largepage_flashbased = {
+        .options = NAND_BBT_SCANEMPTY | NAND_BBT_SCANALLPAGES,
+        .offs = 0,
+        .len = 2,
+        .pattern = scan_ff_pattern
+};
+
+static uint8_t scan_agand_pattern[] = { 0x1C, 0x71, 0xC7, 0x1C, 0x71, 0xC7 };
+
+static struct nand_bbt_descr agand_flashbased = {
+        .options = NAND_BBT_SCANEMPTY | NAND_BBT_SCANALLPAGES,
+        .offs = 0x20,
+        .len = 6,
+        .pattern = scan_agand_pattern
+};
+
+/* Generic flash bbt decriptors
+*/
+static uint8_t bbt_pattern[] = {'B', 'b', 't', '0' };
+static uint8_t mirror_pattern[] = {'1', 't', 'b', 'B' };
+
+static struct nand_bbt_descr bbt_main_descr = {
+        .options = NAND_BBT_LASTBLOCK | NAND_BBT_CREATE | NAND_BBT_WRITE 
+                | NAND_BBT_2BIT | NAND_BBT_VERSION | NAND_BBT_PERCHIP,
+        .offs = 8,
+        .len = 4,
+        .veroffs = 12,
+        .maxblocks = 4,
+        .pattern = bbt_pattern
+};
+
+static struct nand_bbt_descr bbt_mirror_descr = {
+        .options = NAND_BBT_LASTBLOCK | NAND_BBT_CREATE | NAND_BBT_WRITE 
+                | NAND_BBT_2BIT | NAND_BBT_VERSION | NAND_BBT_PERCHIP,
+        .offs = 8,
+        .len = 4,
+        .veroffs = 12,
+        .maxblocks = 4,
+        .pattern = mirror_pattern
+};
+
+/**
+ * nand_default_bbt - [NAND Interface] Select a default bad block table for the device 
+ * @mtd:        MTD device structure
+ *
+ * This function selects the default bad block table
+ * support for the device and calls the nand_scan_bbt function
+ *
+*/
+int nand_default_bbt (struct mtd_info *mtd)
+{
+        struct nand_chip *this = mtd->priv;
+        
+        /* Default for AG-AND. We must use a flash based 
+         * bad block table as the devices have factory marked
+         * _good_ blocks. Erasing those blocks leads to loss
+         * of the good / bad information, so we _must_ store
+         * this information in a good / bad table during 
+         * startup
+        */
+        if (this->options & NAND_IS_AND) {
+                /* Use the default pattern descriptors */
+                if (!this->bbt_td) {    
+                        this->bbt_td = &bbt_main_descr;
+                        this->bbt_md = &bbt_mirror_descr;
+                }       
+                this->options |= NAND_USE_FLASH_BBT;
+                return nand_scan_bbt (mtd, &agand_flashbased);
+        }
+        
+        
+        /* Is a flash based bad block table requested ? */
+        if (this->options & NAND_USE_FLASH_BBT) {
+                /* Use the default pattern descriptors */       
+                if (!this->bbt_td) {    
+                        this->bbt_td = &bbt_main_descr;
+                        this->bbt_md = &bbt_mirror_descr;
+                }
+                if (!this->badblock_pattern) {
+                        this->badblock_pattern = (mtd->oobblock > 512) ?
+                                &largepage_flashbased : &smallpage_flashbased;
+                }
+        } else {
+                this->bbt_td = NULL;
+                this->bbt_md = NULL;
+                if (!this->badblock_pattern) {
+                        this->badblock_pattern = (mtd->oobblock > 512) ?
+                                &largepage_memorybased : &smallpage_memorybased;
+                }
+        }
+        return nand_scan_bbt (mtd, this->badblock_pattern);
+}
+
+/**
+ * nand_isbad_bbt - [NAND Interface] Check if a block is bad 
+ * @mtd:        MTD device structure
+ * @offs:       offset in the device
+ * @allowbbt:   allow access to bad block table region
+ *
+*/
+int nand_isbad_bbt (struct mtd_info *mtd, loff_t offs, int allowbbt)
+{
+        struct nand_chip *this = mtd->priv;
+        int block;
+        uint8_t res;
+        
+        /* Get block number * 2 */
+        block = (int) (offs >> (this->bbt_erase_shift - 1));
+        res = (this->bbt[block >> 3] >> (block & 0x06)) & 0x03;
+
+        DEBUG (MTD_DEBUG_LEVEL2, "nand_isbad_bbt(): bbt info for offs 0x%08x: (block %d) 0x%02x\n", 
+                (unsigned int)offs, res, block >> 1);
+
+        switch ((int)res) {
+        case 0x00:      return 0;
+        case 0x01:      return 1;
+        case 0x02:      return allowbbt ? 0 : 1;
+        }
+        return 1;
+}
+
+EXPORT_SYMBOL (nand_scan_bbt);
+EXPORT_SYMBOL (nand_default_bbt);