[mirror_ubuntu-hirsute-kernel.git] / drivers / mtd / nand / raw / nand_bbt.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  Overview:
 *   Bad block table support for the NAND driver
 *
 *  Copyright © 2004 Thomas Gleixner (tglx@linutronix.de)
 *
 * 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, then 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 * If one of the BBTs is out of date or does not exist it is (re)created.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/bbm.h>
#include <linux/bitops.h>
#include <linux/delay.h>
#include <linux/vmalloc.h>
#include <linux/export.h>
#include <linux/string.h>

#include "internals.h"

#define BBT_BLOCK_GOOD          0x00
#define BBT_BLOCK_WORN          0x01
#define BBT_BLOCK_RESERVED      0x02
#define BBT_BLOCK_FACTORY_BAD   0x03

#define BBT_ENTRY_MASK          0x03
#define BBT_ENTRY_SHIFT         2

static inline uint8_t bbt_get_entry(struct nand_chip *chip, int block)
{
        uint8_t entry = chip->bbt[block >> BBT_ENTRY_SHIFT];
        entry >>= (block & BBT_ENTRY_MASK) * 2;
        return entry & BBT_ENTRY_MASK;
}

static inline void bbt_mark_entry(struct nand_chip *chip, int block,
                uint8_t mark)
{
        uint8_t msk = (mark & BBT_ENTRY_MASK) << ((block & BBT_ENTRY_MASK) * 2);
        chip->bbt[block >> BBT_ENTRY_SHIFT] |= msk;
}

static int check_pattern_no_oob(uint8_t *buf, struct nand_bbt_descr *td)
{
        if (memcmp(buf, td->pattern, td->len))
                return -1;
        return 0;
}

/**
 * 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.
 */
static int check_pattern(uint8_t *buf, int len, int paglen, struct nand_bbt_descr *td)
{
        if (td->options & NAND_BBT_NO_OOB)
                return check_pattern_no_oob(buf, td);

        /* Compare the pattern */
        if (memcmp(buf + paglen + td->offs, td->pattern, td->len))
                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)
{
        /* Compare the pattern */
        if (memcmp(buf + td->offs, td->pattern, td->len))
                return -1;
        return 0;
}

/**
 * add_marker_len - compute the length of the marker in data area
 * @td: BBT descriptor used for computation
 *
 * The length will be 0 if the marker is located in OOB area.
 */
static u32 add_marker_len(struct nand_bbt_descr *td)
{
        u32 len;

        if (!(td->options & NAND_BBT_NO_OOB))
                return 0;

        len = td->len;
        if (td->options & NAND_BBT_VERSION)
                len++;
        return len;
}

/**
 * read_bbt - [GENERIC] Read the bad block table starting from page
 * @this: NAND chip object
 * @buf: temporary buffer
 * @page: the starting page
 * @num: the number of bbt descriptors to read
 * @td: the bbt describtion table
 * @offs: block number offset in the table
 *
 * Read the bad block table starting from page.
 */
static int read_bbt(struct nand_chip *this, uint8_t *buf, int page, int num,
                    struct nand_bbt_descr *td, int offs)
{
        struct mtd_info *mtd = nand_to_mtd(this);
        int res, ret = 0, i, j, act = 0;
        size_t retlen, len, totlen;
        loff_t from;
        int bits = td->options & NAND_BBT_NRBITS_MSK;
        uint8_t msk = (uint8_t)((1 << bits) - 1);
        u32 marker_len;
        int reserved_block_code = td->reserved_block_code;

        totlen = (num * bits) >> 3;
        marker_len = add_marker_len(td);
        from = ((loff_t)page) << this->page_shift;

        while (totlen) {
                len = min(totlen, (size_t)(1 << this->bbt_erase_shift));
                if (marker_len) {
                        /*
                         * In case the BBT marker is not in the OOB area it
                         * will be just in the first page.
                         */
                        len -= marker_len;
                        from += marker_len;
                        marker_len = 0;
                }
                res = mtd_read(mtd, from, len, &retlen, buf);
                if (res < 0) {
                        if (mtd_is_eccerr(res)) {
                                pr_info("nand_bbt: ECC error in BBT at 0x%012llx\n",
                                        from & ~mtd->writesize);
                                return res;
                        } else if (mtd_is_bitflip(res)) {
                                pr_info("nand_bbt: corrected error in BBT at 0x%012llx\n",
                                        from & ~mtd->writesize);
                                ret = res;
                        } else {
                                pr_info("nand_bbt: error reading BBT\n");
                                return res;
                        }
                }

                /* Analyse data */
                for (i = 0; i < len; i++) {
                        uint8_t dat = buf[i];
                        for (j = 0; j < 8; j += bits, act++) {
                                uint8_t tmp = (dat >> j) & msk;
                                if (tmp == msk)
                                        continue;
                                if (reserved_block_code && (tmp == reserved_block_code)) {
                                        pr_info("nand_read_bbt: reserved block at 0x%012llx\n",
                                                 (loff_t)(offs + act) <<
                                                 this->bbt_erase_shift);
                                        bbt_mark_entry(this, offs + act,
                                                        BBT_BLOCK_RESERVED);
                                        mtd->ecc_stats.bbtblocks++;
                                        continue;
                                }
                                /*
                                 * Leave it for now, if it's matured we can
                                 * move this message to pr_debug.
                                 */
                                pr_info("nand_read_bbt: bad block at 0x%012llx\n",
                                         (loff_t)(offs + act) <<
                                         this->bbt_erase_shift);
                                /* Factory marked bad or worn out? */
                                if (tmp == 0)
                                        bbt_mark_entry(this, offs + act,
                                                        BBT_BLOCK_FACTORY_BAD);
                                else
                                        bbt_mark_entry(this, offs + act,
                                                        BBT_BLOCK_WORN);
                                mtd->ecc_stats.badblocks++;
                        }
                }
                totlen -= len;
                from += len;
        }
        return ret;
}

/**
 * read_abs_bbt - [GENERIC] Read the bad block table starting at a given page
 * @this: NAND chip object
 * @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 nand_chip *this, uint8_t *buf,
                        struct nand_bbt_descr *td, int chip)
{
        struct mtd_info *mtd = nand_to_mtd(this);
        u64 targetsize = nanddev_target_size(&this->base);
        int res = 0, i;

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

/* BBT marker is in the first page, no OOB */
static int scan_read_data(struct nand_chip *this, uint8_t *buf, loff_t offs,
                          struct nand_bbt_descr *td)
{
        struct mtd_info *mtd = nand_to_mtd(this);
        size_t retlen;
        size_t len;

        len = td->len;
        if (td->options & NAND_BBT_VERSION)
                len++;

        return mtd_read(mtd, offs, len, &retlen, buf);
}

/**
 * scan_read_oob - [GENERIC] Scan data+OOB region to buffer
 * @this: NAND chip object
 * @buf: temporary buffer
 * @offs: offset at which to scan
 * @len: length of data region to read
 *
 * Scan read data from data+OOB. May traverse multiple pages, interleaving
 * page,OOB,page,OOB,... in buf. Completes transfer and returns the "strongest"
 * ECC condition (error or bitflip). May quit on the first (non-ECC) error.
 */
static int scan_read_oob(struct nand_chip *this, uint8_t *buf, loff_t offs,
                         size_t len)
{
        struct mtd_info *mtd = nand_to_mtd(this);
        struct mtd_oob_ops ops;
        int res, ret = 0;

        ops.mode = MTD_OPS_PLACE_OOB;
        ops.ooboffs = 0;
        ops.ooblen = mtd->oobsize;

        while (len > 0) {
                ops.datbuf = buf;
                ops.len = min(len, (size_t)mtd->writesize);
                ops.oobbuf = buf + ops.len;

                res = mtd_read_oob(mtd, offs, &ops);
                if (res) {
                        if (!mtd_is_bitflip_or_eccerr(res))
                                return res;
                        else if (mtd_is_eccerr(res) || !ret)
                                ret = res;
                }

                buf += mtd->oobsize + mtd->writesize;
                len -= mtd->writesize;
                offs += mtd->writesize;
        }
        return ret;
}

static int scan_read(struct nand_chip *this, uint8_t *buf, loff_t offs,
                     size_t len, struct nand_bbt_descr *td)
{
        if (td->options & NAND_BBT_NO_OOB)
                return scan_read_data(this, buf, offs, td);
        else
                return scan_read_oob(this, buf, offs, len);
}

/* Scan write data with oob to flash */
static int scan_write_bbt(struct nand_chip *this, loff_t offs, size_t len,
                          uint8_t *buf, uint8_t *oob)
{
        struct mtd_info *mtd = nand_to_mtd(this);
        struct mtd_oob_ops ops;

        ops.mode = MTD_OPS_PLACE_OOB;
        ops.ooboffs = 0;
        ops.ooblen = mtd->oobsize;
        ops.datbuf = buf;
        ops.oobbuf = oob;
        ops.len = len;

        return mtd_write_oob(mtd, offs, &ops);
}

static u32 bbt_get_ver_offs(struct nand_chip *this, struct nand_bbt_descr *td)
{
        struct mtd_info *mtd = nand_to_mtd(this);
        u32 ver_offs = td->veroffs;

        if (!(td->options & NAND_BBT_NO_OOB))
                ver_offs += mtd->writesize;
        return ver_offs;
}

/**
 * read_abs_bbts - [GENERIC] Read the bad block table(s) for all chips starting at a given page
 * @this: NAND chip object
 * @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 void read_abs_bbts(struct nand_chip *this, uint8_t *buf,
                          struct nand_bbt_descr *td, struct nand_bbt_descr *md)
{
        struct mtd_info *mtd = nand_to_mtd(this);

        /* Read the primary version, if available */
        if (td->options & NAND_BBT_VERSION) {
                scan_read(this, buf, (loff_t)td->pages[0] << this->page_shift,
                          mtd->writesize, td);
                td->version[0] = buf[bbt_get_ver_offs(this, td)];
                pr_info("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)) {
                scan_read(this, buf, (loff_t)md->pages[0] << this->page_shift,
                          mtd->writesize, md);
                md->version[0] = buf[bbt_get_ver_offs(this, md)];
                pr_info("Bad block table at page %d, version 0x%02X\n",
                         md->pages[0], md->version[0]);
        }
}

/* Scan a given block partially */
static int scan_block_fast(struct nand_chip *this, struct nand_bbt_descr *bd,
                           loff_t offs, uint8_t *buf)
{
        struct mtd_info *mtd = nand_to_mtd(this);

        struct mtd_oob_ops ops;
        int ret, page_offset;

        ops.ooblen = mtd->oobsize;
        ops.oobbuf = buf;
        ops.ooboffs = 0;
        ops.datbuf = NULL;
        ops.mode = MTD_OPS_PLACE_OOB;

        page_offset = nand_bbm_get_next_page(this, 0);

        while (page_offset >= 0) {
                /*
                 * Read the full oob until read_oob is fixed to handle single
                 * byte reads for 16 bit buswidth.
                 */
                ret = mtd_read_oob(mtd, offs + (page_offset * mtd->writesize),
                                   &ops);
                /* Ignore ECC errors when checking for BBM */
                if (ret && !mtd_is_bitflip_or_eccerr(ret))
                        return ret;

                if (check_short_pattern(buf, bd))
                        return 1;

                page_offset = nand_bbm_get_next_page(this, page_offset + 1);
        }

        return 0;
}

/**
 * create_bbt - [GENERIC] Create a bad block table by scanning the device
 * @this: NAND chip object
 * @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 nand_chip *this, uint8_t *buf,
                      struct nand_bbt_descr *bd, int chip)
{
        u64 targetsize = nanddev_target_size(&this->base);
        struct mtd_info *mtd = nand_to_mtd(this);
        int i, numblocks, startblock;
        loff_t from;

        pr_info("Scanning device for bad blocks\n");

        if (chip == -1) {
                numblocks = mtd->size >> this->bbt_erase_shift;
                startblock = 0;
                from = 0;
        } else {
                if (chip >= nanddev_ntargets(&this->base)) {
                        pr_warn("create_bbt(): chipnr (%d) > available chips (%d)\n",
                                chip + 1, nanddev_ntargets(&this->base));
                        return -EINVAL;
                }
                numblocks = targetsize >> this->bbt_erase_shift;
                startblock = chip * numblocks;
                numblocks += startblock;
                from = (loff_t)startblock << this->bbt_erase_shift;
        }

        for (i = startblock; i < numblocks; i++) {
                int ret;

                BUG_ON(bd->options & NAND_BBT_NO_OOB);

                ret = scan_block_fast(this, bd, from, buf);
                if (ret < 0)
                        return ret;

                if (ret) {
                        bbt_mark_entry(this, i, BBT_BLOCK_FACTORY_BAD);
                        pr_warn("Bad eraseblock %d at 0x%012llx\n",
                                i, (unsigned long long)from);
                        mtd->ecc_stats.badblocks++;
                }

                from += (1 << this->bbt_erase_shift);
        }
        return 0;
}

/**
 * search_bbt - [GENERIC] scan the device for a specific bad block table
 * @this: NAND chip object
 * @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 necessary 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 nand_chip *this, uint8_t *buf,
                      struct nand_bbt_descr *td)
{
        u64 targetsize = nanddev_target_size(&this->base);
        struct mtd_info *mtd = nand_to_mtd(this);
        int i, chips;
        int startblock, block, dir;
        int scanlen = mtd->writesize + mtd->oobsize;
        int bbtblocks;
        int blocktopage = this->bbt_erase_shift - this->page_shift;

        /* 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 = nanddev_ntargets(&this->base);
                bbtblocks = targetsize >> this->bbt_erase_shift;
                startblock &= bbtblocks - 1;
        } else {
                chips = 1;
                bbtblocks = mtd->size >> this->bbt_erase_shift;
        }

        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;
                        loff_t offs = (loff_t)actblock << this->bbt_erase_shift;

                        /* Read first page */
                        scan_read(this, buf, offs, mtd->writesize, td);
                        if (!check_pattern(buf, scanlen, mtd->writesize, td)) {
                                td->pages[i] = actblock << blocktopage;
                                if (td->options & NAND_BBT_VERSION) {
                                        offs = bbt_get_ver_offs(this, td);
                                        td->version[i] = buf[offs];
                                }
                                break;
                        }
                }
                startblock += targetsize >> 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)
                        pr_warn("Bad block table not found for chip %d\n", i);
                else
                        pr_info("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)
 * @this: NAND chip object
 * @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 void search_read_bbts(struct nand_chip *this, uint8_t *buf,
                             struct nand_bbt_descr *td,
                             struct nand_bbt_descr *md)
{
        /* Search the primary table */
        search_bbt(this, buf, td);

        /* Search the mirror table */
        if (md)
                search_bbt(this, buf, md);
}

/**
 * get_bbt_block - Get the first valid eraseblock suitable to store a BBT
 * @this: the NAND device
 * @td: the BBT description
 * @md: the mirror BBT descriptor
 * @chip: the CHIP selector
 *
 * This functions returns a positive block number pointing a valid eraseblock
 * suitable to store a BBT (i.e. in the range reserved for BBT), or -ENOSPC if
 * all blocks are already used of marked bad. If td->pages[chip] was already
 * pointing to a valid block we re-use it, otherwise we search for the next
 * valid one.
 */
static int get_bbt_block(struct nand_chip *this, struct nand_bbt_descr *td,
                         struct nand_bbt_descr *md, int chip)
{
        u64 targetsize = nanddev_target_size(&this->base);
        int startblock, dir, page, numblocks, i;

        /*
         * There was already a version of the table, reuse the page. This
         * applies for absolute placement too, as we have the page number in
         * td->pages.
         */
        if (td->pages[chip] != -1)
                return td->pages[chip] >>
                                (this->bbt_erase_shift - this->page_shift);

        numblocks = (int)(targetsize >> this->bbt_erase_shift);
        if (!(td->options & NAND_BBT_PERCHIP))
                numblocks *= nanddev_ntargets(&this->base);

        /*
         * 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 (bbt_get_entry(this, block)) {
                case BBT_BLOCK_WORN:
                case BBT_BLOCK_FACTORY_BAD:
                        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)
                        return block;
        }

        return -ENOSPC;
}

/**
 * mark_bbt_block_bad - Mark one of the block reserved for BBT bad
 * @this: the NAND device
 * @td: the BBT description
 * @chip: the CHIP selector
 * @block: the BBT block to mark
 *
 * Blocks reserved for BBT can become bad. This functions is an helper to mark
 * such blocks as bad. It takes care of updating the in-memory BBT, marking the
 * block as bad using a bad block marker and invalidating the associated
 * td->pages[] entry.
 */
static void mark_bbt_block_bad(struct nand_chip *this,
                               struct nand_bbt_descr *td,
                               int chip, int block)
{
        loff_t to;
        int res;

        bbt_mark_entry(this, block, BBT_BLOCK_WORN);

        to = (loff_t)block << this->bbt_erase_shift;
        res = nand_markbad_bbm(this, to);
        if (res)
                pr_warn("nand_bbt: error %d while marking block %d bad\n",
                        res, block);

        td->pages[chip] = -1;
}

/**
 * write_bbt - [GENERIC] (Re)write the bad block table
 * @this: NAND chip object
 * @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 nand_chip *this, uint8_t *buf,
                     struct nand_bbt_descr *td, struct nand_bbt_descr *md,
                     int chipsel)
{
        u64 targetsize = nanddev_target_size(&this->base);
        struct mtd_info *mtd = nand_to_mtd(this);
        struct erase_info einfo;
        int i, res, chip = 0;
        int bits, page, offs, numblocks, sft, sftmsk;
        int nrchips, pageoffs, ooboffs;
        uint8_t msk[4];
        uint8_t rcode = td->reserved_block_code;
        size_t retlen, len = 0;
        loff_t to;
        struct mtd_oob_ops ops;

        ops.ooblen = mtd->oobsize;
        ops.ooboffs = 0;
        ops.datbuf = NULL;
        ops.mode = MTD_OPS_PLACE_OOB;

        if (!rcode)
                rcode = 0xff;
        /* Write bad block table per chip rather than per device? */
        if (td->options & NAND_BBT_PERCHIP) {
                numblocks = (int)(targetsize >> this->bbt_erase_shift);
                /* Full device write or specific chip? */
                if (chipsel == -1) {
                        nrchips = nanddev_ntargets(&this->base);
                } else {
                        nrchips = chipsel + 1;
                        chip = chipsel;
                }
        } else {
                numblocks = (int)(mtd->size >> this->bbt_erase_shift);
                nrchips = 1;
        }

        /* Loop through the chips */
        while (chip < nrchips) {
                int block;

                block = get_bbt_block(this, td, md, chip);
                if (block < 0) {
                        pr_err("No space left to write bad block table\n");
                        res = block;
                        goto outerr;
                }

                /*
                 * get_bbt_block() returns a block number, shift the value to
                 * get a page number.
                 */
                page = block << (this->bbt_erase_shift - this->page_shift);

                /* Set up shift count and masks for the flash table */
                bits = td->options & NAND_BBT_NRBITS_MSK;
                msk[2] = ~rcode;
                switch (bits) {
                case 1: sft = 3; sftmsk = 0x07; msk[0] = 0x00; msk[1] = 0x01;
                        msk[3] = 0x01;
                        break;
                case 2: sft = 2; sftmsk = 0x06; msk[0] = 0x00; msk[1] = 0x01;
                        msk[3] = 0x03;
                        break;
                case 4: sft = 1; sftmsk = 0x04; msk[0] = 0x00; msk[1] = 0x0C;
                        msk[3] = 0x0f;
                        break;
                case 8: sft = 0; sftmsk = 0x00; msk[0] = 0x00; msk[1] = 0x0F;
                        msk[3] = 0xff;
                        break;
                default: return -EINVAL;
                }

                to = ((loff_t)page) << this->page_shift;

                /* 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(mtd, to, len, &retlen, buf);
                        if (res < 0) {
                                if (retlen != len) {
                                        pr_info("nand_bbt: error reading block for writing the bad block table\n");
                                        return res;
                                }
                                pr_warn("nand_bbt: ECC error while reading block for writing bad block table\n");
                        }
                        /* Read oob data */
                        ops.ooblen = (len >> this->page_shift) * mtd->oobsize;
                        ops.oobbuf = &buf[len];
                        res = mtd_read_oob(mtd, to + mtd->writesize, &ops);
                        if (res < 0 || ops.oobretlen != ops.ooblen)
                                goto outerr;

                        /* 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));
                        ooboffs = len + (pageoffs * mtd->oobsize);

                } else if (td->options & NAND_BBT_NO_OOB) {
                        ooboffs = 0;
                        offs = td->len;
                        /* The version byte */
                        if (td->options & NAND_BBT_VERSION)
                                offs++;
                        /* Calc length */
                        len = (size_t)(numblocks >> sft);
                        len += offs;
                        /* Make it page aligned! */
                        len = ALIGN(len, mtd->writesize);
                        /* Preset the buffer with 0xff */
                        memset(buf, 0xff, len);
                        /* Pattern is located at the begin of first page */
                        memcpy(buf, td->pattern, td->len);
                } else {
                        /* Calc length */
                        len = (size_t)(numblocks >> sft);
                        /* Make it page aligned! */
                        len = ALIGN(len, mtd->writesize);
                        /* Preset the buffer with 0xff */
                        memset(buf, 0xff, len +
                               (len >> this->page_shift)* mtd->oobsize);
                        offs = 0;
                        ooboffs = len;
                        /* Pattern is located in oob area of first page */
                        memcpy(&buf[ooboffs + td->offs], td->pattern, td->len);
                }

                if (td->options & NAND_BBT_VERSION)
                        buf[ooboffs + td->veroffs] = td->version[chip];

                /* Walk through the memory table */
                for (i = 0; i < numblocks; i++) {
                        uint8_t dat;
                        int sftcnt = (i << (3 - sft)) & sftmsk;
                        dat = bbt_get_entry(this, chip * numblocks + i);
                        /* Do not store the reserved bbt blocks! */
                        buf[offs + (i >> sft)] &= ~(msk[dat] << sftcnt);
                }

                memset(&einfo, 0, sizeof(einfo));
                einfo.addr = to;
                einfo.len = 1 << this->bbt_erase_shift;
                res = nand_erase_nand(this, &einfo, 1);
                if (res < 0) {
                        pr_warn("nand_bbt: error while erasing BBT block %d\n",
                                res);
                        mark_bbt_block_bad(this, td, chip, block);
                        continue;
                }

                res = scan_write_bbt(this, to, len, buf,
                                     td->options & NAND_BBT_NO_OOB ?
                                     NULL : &buf[len]);
                if (res < 0) {
                        pr_warn("nand_bbt: error while writing BBT block %d\n",
                                res);
                        mark_bbt_block_bad(this, td, chip, block);
                        continue;
                }

                pr_info("Bad block table written to 0x%012llx, version 0x%02X\n",
                         (unsigned long long)to, td->version[chip]);

                /* Mark it as used */
                td->pages[chip++] = page;
        }
        return 0;

 outerr:
        pr_warn("nand_bbt: error while writing bad block table %d\n", res);
        return res;
}

/**
 * nand_memory_bbt - [GENERIC] create a memory based bad block table
 * @this: NAND chip object
 * @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 inline int nand_memory_bbt(struct nand_chip *this,
                                  struct nand_bbt_descr *bd)
{
        u8 *pagebuf = nand_get_data_buf(this);

        return create_bbt(this, pagebuf, bd, -1);
}

/**
 * check_create - [GENERIC] create and write bbt(s) if necessary
 * @this: the NAND device
 * @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 necessary. Creation is necessary if no bbt was found
 * for the chip/device. Update is necessary if one of the tables is missing or
 * the version nr. of one table is less than the other.
 */
static int check_create(struct nand_chip *this, uint8_t *buf,
                        struct nand_bbt_descr *bd)
{
        int i, chips, writeops, create, chipsel, res, res2;
        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 = nanddev_ntargets(&this->base);
        else
                chips = 1;

        for (i = 0; i < chips; i++) {
                writeops = 0;
                create = 0;
                rd = NULL;
                rd2 = NULL;
                res = res2 = 0;
                /* Per chip or per device? */
                chipsel = (td->options & NAND_BBT_PERCHIP) ? i : -1;
                /* Mirrored table available? */
                if (md) {
                        if (td->pages[i] == -1 && md->pages[i] == -1) {
                                create = 1;
                                writeops = 0x03;
                        } else if (td->pages[i] == -1) {
                                rd = md;
                                writeops = 0x01;
                        } else if (md->pages[i] == -1) {
                                rd = td;
                                writeops = 0x02;
                        } else if (td->version[i] == md->version[i]) {
                                rd = td;
                                if (!(td->options & NAND_BBT_VERSION))
                                        rd2 = md;
                        } else if (((int8_t)(td->version[i] - md->version[i])) > 0) {
                                rd = td;
                                writeops = 0x02;
                        } else {
                                rd = md;
                                writeops = 0x01;
                        }
                } else {
                        if (td->pages[i] == -1) {
                                create = 1;
                                writeops = 0x01;
                        } else {
                                rd = td;
                        }
                }

                if (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) */
                        if (!(this->bbt_options & NAND_BBT_CREATE_EMPTY))
                                create_bbt(this, buf, bd, chipsel);

                        td->version[i] = 1;
                        if (md)
                                md->version[i] = 1;
                }

                /* Read back first? */
                if (rd) {
                        res = read_abs_bbt(this, buf, rd, chipsel);
                        if (mtd_is_eccerr(res)) {
                                /* Mark table as invalid */
                                rd->pages[i] = -1;
                                rd->version[i] = 0;
                                i--;
                                continue;
                        }
                }
                /* If they weren't versioned, read both */
                if (rd2) {
                        res2 = read_abs_bbt(this, buf, rd2, chipsel);
                        if (mtd_is_eccerr(res2)) {
                                /* Mark table as invalid */
                                rd2->pages[i] = -1;
                                rd2->version[i] = 0;
                                i--;
                                continue;
                        }
                }

                /* Scrub the flash table(s)? */
                if (mtd_is_bitflip(res) || mtd_is_bitflip(res2))
                        writeops = 0x03;

                /* Update version numbers before writing */
                if (md) {
                        td->version[i] = max(td->version[i], md->version[i]);
                        md->version[i] = td->version[i];
                }

                /* Write the bad block table to the device? */
                if ((writeops & 0x01) && (td->options & NAND_BBT_WRITE)) {
                        res = write_bbt(this, 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(this, buf, md, td, chipsel);
                        if (res < 0)
                                return res;
                }
        }
        return 0;
}

/**
 * nand_update_bbt - update bad block table(s)
 * @this: the NAND device
 * @offs: the offset of the newly marked block
 *
 * The function updates the bad block table(s).
 */
static int nand_update_bbt(struct nand_chip *this, loff_t offs)
{
        struct mtd_info *mtd = nand_to_mtd(this);
        int len, res = 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;

        /* 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)
                return -ENOMEM;

        /* 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 (td->options & NAND_BBT_WRITE) {
                res = write_bbt(this, buf, td, md, chipsel);
                if (res < 0)
                        goto out;
        }
        /* Write the mirror bad block table to the device? */
        if (md && (md->options & NAND_BBT_WRITE)) {
                res = write_bbt(this, buf, md, td, chipsel);
        }

 out:
        kfree(buf);
        return res;
}

/**
 * mark_bbt_regions - [GENERIC] mark the bad block table regions
 * @this: the NAND device
 * @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 nand_chip *this, struct nand_bbt_descr *td)
{
        u64 targetsize = nanddev_target_size(&this->base);
        struct mtd_info *mtd = nand_to_mtd(this);
        int i, j, chips, block, nrblocks, update;
        uint8_t oldval;

        /* Do we have a bbt per chip? */
        if (td->options & NAND_BBT_PERCHIP) {
                chips = nanddev_ntargets(&this->base);
                nrblocks = (int)(targetsize >> 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);
                        oldval = bbt_get_entry(this, block);
                        bbt_mark_entry(this, block, BBT_BLOCK_RESERVED);
                        if ((oldval != BBT_BLOCK_RESERVED) &&
                                        td->reserved_block_code)
                                nand_update_bbt(this, (loff_t)block <<
                                                this->bbt_erase_shift);
                        continue;
                }
                update = 0;
                if (td->options & NAND_BBT_LASTBLOCK)
                        block = ((i + 1) * nrblocks) - td->maxblocks;
                else
                        block = i * nrblocks;
                for (j = 0; j < td->maxblocks; j++) {
                        oldval = bbt_get_entry(this, block);
                        bbt_mark_entry(this, block, BBT_BLOCK_RESERVED);
                        if (oldval != BBT_BLOCK_RESERVED)
                                update = 1;
                        block++;
                }
                /*
                 * 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(this, (loff_t)(block - 1) <<
                                        this->bbt_erase_shift);
        }
}

/**
 * verify_bbt_descr - verify the bad block description
 * @this: the NAND device
 * @bd: the table to verify
 *
 * This functions performs a few sanity checks on the bad block description
 * table.
 */
static void verify_bbt_descr(struct nand_chip *this, struct nand_bbt_descr *bd)
{
        u64 targetsize = nanddev_target_size(&this->base);
        struct mtd_info *mtd = nand_to_mtd(this);
        u32 pattern_len;
        u32 bits;
        u32 table_size;

        if (!bd)
                return;

        pattern_len = bd->len;
        bits = bd->options & NAND_BBT_NRBITS_MSK;

        BUG_ON((this->bbt_options & NAND_BBT_NO_OOB) &&
                        !(this->bbt_options & NAND_BBT_USE_FLASH));
        BUG_ON(!bits);

        if (bd->options & NAND_BBT_VERSION)
                pattern_len++;

        if (bd->options & NAND_BBT_NO_OOB) {
                BUG_ON(!(this->bbt_options & NAND_BBT_USE_FLASH));
                BUG_ON(!(this->bbt_options & NAND_BBT_NO_OOB));
                BUG_ON(bd->offs);
                if (bd->options & NAND_BBT_VERSION)
                        BUG_ON(bd->veroffs != bd->len);
                BUG_ON(bd->options & NAND_BBT_SAVECONTENT);
        }

        if (bd->options & NAND_BBT_PERCHIP)
                table_size = targetsize >> this->bbt_erase_shift;
        else
                table_size = mtd->size >> this->bbt_erase_shift;
        table_size >>= 3;
        table_size *= bits;
        if (bd->options & NAND_BBT_NO_OOB)
                table_size += pattern_len;
        BUG_ON(table_size > (1 << this->bbt_erase_shift));
}

/**
 * nand_scan_bbt - [NAND Interface] scan, find, read and maybe create bad block table(s)
 * @this: the NAND device
 * @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.
 */
static int nand_scan_bbt(struct nand_chip *this, struct nand_bbt_descr *bd)
{
        struct mtd_info *mtd = nand_to_mtd(this);
        int len, res;
        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)) ? : 1;
        /*
         * Allocate memory (2bit per block) and clear the memory bad block
         * table.
         */
        this->bbt = kzalloc(len, GFP_KERNEL);
        if (!this->bbt)
                return -ENOMEM;

        /*
         * If no primary table decriptor is given, scan the device to build a
         * memory based bad block table.
         */
        if (!td) {
                if ((res = nand_memory_bbt(this, bd))) {
                        pr_err("nand_bbt: can't scan flash and build the RAM-based BBT\n");
                        goto err;
                }
                return 0;
        }
        verify_bbt_descr(this, td);
        verify_bbt_descr(this, md);

        /* Allocate a temporary buffer for one eraseblock incl. oob */
        len = (1 << this->bbt_erase_shift);
        len += (len >> this->page_shift) * mtd->oobsize;
        buf = vmalloc(len);
        if (!buf) {
                res = -ENOMEM;
                goto err;
        }

        /* Is the bbt at a given page? */
        if (td->options & NAND_BBT_ABSPAGE) {
                read_abs_bbts(this, buf, td, md);
        } else {
                /* Search the bad block table using a pattern in oob */
                search_read_bbts(this, buf, td, md);
        }

        res = check_create(this, buf, bd);
        if (res)
                goto err;

        /* Prevent the bbt regions from erasing / writing */
        mark_bbt_region(this, td);
        if (md)
                mark_bbt_region(this, md);

        vfree(buf);
        return 0;

err:
        kfree(this->bbt);
        this->bbt = NULL;
        return res;
}

/*
 * Define some generic bad / good block scan pattern which are used
 * while scanning a device for factory marked good / bad blocks.
 */
static uint8_t scan_ff_pattern[] = { 0xff, 0xff };

/* Generic flash bbt descriptors */
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 = NAND_BBT_SCAN_MAXBLOCKS,
        .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 = NAND_BBT_SCAN_MAXBLOCKS,
        .pattern = mirror_pattern
};

static struct nand_bbt_descr bbt_main_no_oob_descr = {
        .options = NAND_BBT_LASTBLOCK | NAND_BBT_CREATE | NAND_BBT_WRITE
                | NAND_BBT_2BIT | NAND_BBT_VERSION | NAND_BBT_PERCHIP
                | NAND_BBT_NO_OOB,
        .len = 4,
        .veroffs = 4,
        .maxblocks = NAND_BBT_SCAN_MAXBLOCKS,
        .pattern = bbt_pattern
};

static struct nand_bbt_descr bbt_mirror_no_oob_descr = {
        .options = NAND_BBT_LASTBLOCK | NAND_BBT_CREATE | NAND_BBT_WRITE
                | NAND_BBT_2BIT | NAND_BBT_VERSION | NAND_BBT_PERCHIP
                | NAND_BBT_NO_OOB,
        .len = 4,
        .veroffs = 4,
        .maxblocks = NAND_BBT_SCAN_MAXBLOCKS,
        .pattern = mirror_pattern
};

#define BADBLOCK_SCAN_MASK (~NAND_BBT_NO_OOB)
/**
 * nand_create_badblock_pattern - [INTERN] Creates a BBT descriptor structure
 * @this: NAND chip to create descriptor for
 *
 * This function allocates and initializes a nand_bbt_descr for BBM detection
 * based on the properties of @this. The new descriptor is stored in
 * this->badblock_pattern. Thus, this->badblock_pattern should be NULL when
 * passed to this function.
 */
static int nand_create_badblock_pattern(struct nand_chip *this)
{
        struct nand_bbt_descr *bd;
        if (this->badblock_pattern) {
                pr_warn("Bad block pattern already allocated; not replacing\n");
                return -EINVAL;
        }
        bd = kzalloc(sizeof(*bd), GFP_KERNEL);
        if (!bd)
                return -ENOMEM;
        bd->options = this->bbt_options & BADBLOCK_SCAN_MASK;
        bd->offs = this->badblockpos;
        bd->len = (this->options & NAND_BUSWIDTH_16) ? 2 : 1;
        bd->pattern = scan_ff_pattern;
        bd->options |= NAND_BBT_DYNAMICSTRUCT;
        this->badblock_pattern = bd;
        return 0;
}

/**
 * nand_create_bbt - [NAND Interface] Select a default bad block table for the device
 * @this: NAND chip object
 *
 * This function selects the default bad block table support for the device and
 * calls the nand_scan_bbt function.
 */
int nand_create_bbt(struct nand_chip *this)
{
        int ret;

        /* Is a flash based bad block table requested? */
        if (this->bbt_options & NAND_BBT_USE_FLASH) {
                /* Use the default pattern descriptors */
                if (!this->bbt_td) {
                        if (this->bbt_options & NAND_BBT_NO_OOB) {
                                this->bbt_td = &bbt_main_no_oob_descr;
                                this->bbt_md = &bbt_mirror_no_oob_descr;
                        } else {
                                this->bbt_td = &bbt_main_descr;
                                this->bbt_md = &bbt_mirror_descr;
                        }
                }
        } else {
                this->bbt_td = NULL;
                this->bbt_md = NULL;
        }

        if (!this->badblock_pattern) {
                ret = nand_create_badblock_pattern(this);
                if (ret)
                        return ret;
        }

        return nand_scan_bbt(this, this->badblock_pattern);
}
EXPORT_SYMBOL(nand_create_bbt);

/**
 * nand_isreserved_bbt - [NAND Interface] Check if a block is reserved
 * @this: NAND chip object
 * @offs: offset in the device
 */
int nand_isreserved_bbt(struct nand_chip *this, loff_t offs)
{
        int block;

        block = (int)(offs >> this->bbt_erase_shift);
        return bbt_get_entry(this, block) == BBT_BLOCK_RESERVED;
}

/**
 * nand_isbad_bbt - [NAND Interface] Check if a block is bad
 * @this: NAND chip object
 * @offs: offset in the device
 * @allowbbt: allow access to bad block table region
 */
int nand_isbad_bbt(struct nand_chip *this, loff_t offs, int allowbbt)
{
        int block, res;

        block = (int)(offs >> this->bbt_erase_shift);
        res = bbt_get_entry(this, block);

        pr_debug("nand_isbad_bbt(): bbt info for offs 0x%08x: (block %d) 0x%02x\n",
                 (unsigned int)offs, block, res);

        switch (res) {
        case BBT_BLOCK_GOOD:
                return 0;
        case BBT_BLOCK_WORN:
                return 1;
        case BBT_BLOCK_RESERVED:
                return allowbbt ? 0 : 1;
        }
        return 1;
}

/**
 * nand_markbad_bbt - [NAND Interface] Mark a block bad in the BBT
 * @this: NAND chip object
 * @offs: offset of the bad block
 */
int nand_markbad_bbt(struct nand_chip *this, loff_t offs)
{
        int block, ret = 0;

        block = (int)(offs >> this->bbt_erase_shift);

        /* Mark bad block in memory */
        bbt_mark_entry(this, block, BBT_BLOCK_WORN);

        /* Update flash-based bad block table */
        if (this->bbt_options & NAND_BBT_USE_FLASH)
                ret = nand_update_bbt(this, offs);

        return ret;
}