/*
 *  linux/drivers/mtd/onenand/onenand_bbt.c
 *
 *  Bad Block Table support for the OneNAND driver
 *
 *  Copyright(c) 2005 Samsung Electronics
 *  Kyungmin Park <kyungmin.park@samsung.com>
 *
 *  Derived from nand_bbt.c
 *
 *  TODO:
 *    Split BBT core and chip specific BBT.
 */

#include <linux/slab.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/onenand.h>

/**
 * check_short_pattern - [GENERIC] check if a pattern is in the buffer
 * @param buf           the buffer to search
 * @param len           the length of buffer to search
 * @param paglen        the pagelength
 * @param 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 and the pattern is expected to start
 * at offset 0.
 *
 */
static int check_short_pattern(uint8_t *buf, int len, int paglen, struct nand_bbt_descr *td)
{
        int i;
        uint8_t *p = buf;

        /* Compare the pattern */
        for (i = 0; i < td->len; i++) {
                if (p[i] != td->pattern[i])
                        return -1;
        }
        return 0;
}

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

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

        len = 2;

        /* We need only read few bytes from the OOB area */
        scanlen = ooblen = 0;
        readlen = bd->len;

        /* chip == -1 case only */
        /* Note that numblocks is 2 * (real numblocks) here;
         * see i += 2 below as it makses shifting and masking less painful
         */
        numblocks = this->chipsize >> (bbm->bbt_erase_shift - 1);
        startblock = 0;
        from = 0;

        ops.mode = MTD_OOB_PLACE;
        ops.ooblen = readlen;
        ops.oobbuf = buf;
        ops.len = ops.ooboffs = ops.retlen = ops.oobretlen = 0;

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

                for (j = 0; j < len; j++) {
                        /* No need to read pages fully,
                         * just read required OOB bytes */
                        ret = onenand_bbt_read_oob(mtd,
                                from + j * this->writesize + bd->offs, &ops);

                        /* If it is a initial bad block, just ignore it */
                        if (ret == ONENAND_BBT_READ_FATAL_ERROR)
                                return -EIO;

                        if (ret || check_short_pattern(&buf[j * scanlen],
                                               scanlen, this->writesize, bd)) {
                                bbm->bbt[i >> 3] |= 0x03 << (i & 0x6);
                                printk(KERN_INFO "OneNAND eraseblock %d is an "
                                        "initial bad block\n", i >> 1);
                                mtd->ecc_stats.badblocks++;
                                break;
                        }
                }
                i += 2;

                if (FLEXONENAND(this)) {
                        rgn = flexonenand_region(mtd, from);
                        from += mtd->eraseregions[rgn].erasesize;
                } else
                        from += (1 << bbm->bbt_erase_shift);
        }

        return 0;
}


/**
 * onenand_memory_bbt - [GENERIC] create a memory based bad block table
 * @param mtd           MTD device structure
 * @param 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 onenand_memory_bbt (struct mtd_info *mtd, struct nand_bbt_descr *bd)
{
        struct onenand_chip *this = mtd->priv;

        bd->options &= ~NAND_BBT_SCANEMPTY;
        return create_bbt(mtd, this->page_buf, bd, -1);
}

/**
 * onenand_isbad_bbt - [OneNAND Interface] Check if a block is bad
 * @param mtd           MTD device structure
 * @param offs          offset in the device
 * @param allowbbt      allow access to bad block table region
 */
static int onenand_isbad_bbt(struct mtd_info *mtd, loff_t offs, int allowbbt)
{
        struct onenand_chip *this = mtd->priv;
        struct bbm_info *bbm = this->bbm;
        int block;
        uint8_t res;

        /* Get block number * 2 */
        block = (int) (onenand_block(this, offs) << 1);
        res = (bbm->bbt[block >> 3] >> (block & 0x06)) & 0x03;

        DEBUG(MTD_DEBUG_LEVEL2, "onenand_isbad_bbt: bbt info for offs 0x%08x: (block %d) 0x%02x\n",
                (unsigned int) offs, block >> 1, res);

        switch ((int) res) {
        case 0x00:      return 0;
        case 0x01:      return 1;
        case 0x02:      return allowbbt ? 0 : 1;
        }

        return 1;
}

/**
 * onenand_scan_bbt - [OneNAND Interface] scan, find, read and maybe create bad block table(s)
 * @param mtd           MTD device structure
 * @param 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 is freed
 * by the onenand_release function.
 *
 */
int onenand_scan_bbt(struct mtd_info *mtd, struct nand_bbt_descr *bd)
{
        struct onenand_chip *this = mtd->priv;
        struct bbm_info *bbm = this->bbm;
        int len, ret = 0;

        len = this->chipsize >> (this->erase_shift + 2);
        /* Allocate memory (2bit per block) and clear the memory bad block table */
        bbm->bbt = kzalloc(len, GFP_KERNEL);
        if (!bbm->bbt) {
                printk(KERN_ERR "onenand_scan_bbt: Out of memory\n");
                return -ENOMEM;
        }

        /* Set the bad block position */
        bbm->badblockpos = ONENAND_BADBLOCK_POS;

        /* Set erase shift */
        bbm->bbt_erase_shift = this->erase_shift;

        if (!bbm->isbad_bbt)
                bbm->isbad_bbt = onenand_isbad_bbt;

        /* Scan the device to build a memory based bad block table */
        if ((ret = onenand_memory_bbt(mtd, bd))) {
                printk(KERN_ERR "onenand_scan_bbt: Can't scan flash and build the RAM-based BBT\n");
                kfree(bbm->bbt);
                bbm->bbt = NULL;
        }

        return ret;
}

/*
 * 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 };

static struct nand_bbt_descr largepage_memorybased = {
        .options = 0,
        .offs = 0,
        .len = 2,
        .pattern = scan_ff_pattern,
};

/**
 * onenand_default_bbt - [OneNAND Interface] Select a default bad block table for the device
 * @param mtd           MTD device structure
 *
 * This function selects the default bad block table
 * support for the device and calls the onenand_scan_bbt function
 */
int onenand_default_bbt(struct mtd_info *mtd)
{
        struct onenand_chip *this = mtd->priv;
        struct bbm_info *bbm;

        this->bbm = kzalloc(sizeof(struct bbm_info), GFP_KERNEL);
        if (!this->bbm)
                return -ENOMEM;

        bbm = this->bbm;

        /* 1KB page has same configuration as 2KB page */
        if (!bbm->badblock_pattern)
                bbm->badblock_pattern = &largepage_memorybased;

        return onenand_scan_bbt(mtd, bbm->badblock_pattern);
}

EXPORT_SYMBOL(onenand_scan_bbt);
EXPORT_SYMBOL(onenand_default_bbt);