/*
* Overview:
* Bad block table support for the NAND driver
*
* Copyright © 2004 Thomas Gleixner (tglx@linutronix.de)
*
* 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 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* If one of the BBTs is out of date or does not exist it is (re)created.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/mtd/rawnand.h>
#include <linux/bitops.h>
#include <linux/delay.h>
#include <linux/vmalloc.h>
#include <linux/export.h>
#include <linux/string.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 int nand_update_bbt(struct mtd_info *mtd, loff_t offs);
static inline uint8_t bbt_get_entry(