text: /*
   *  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>
  #include <linux/export.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_OPS_PLACE_OOB;
  	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;
  
  	pr_debug("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)
  		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);
  