linux/drivers/mtd/sm_ftl.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright © 2009 - Maxim Levitsky
 * SmartMedia/xD translation layer
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/random.h>
#include <linux/hdreg.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
#include <linux/sysfs.h>
#include <linux/bitops.h>
#include <linux/slab.h>
#include <linux/mtd/nand-ecc-sw-hamming.h>
#include "nand/raw/sm_common.h"
#include "sm_ftl.h"



static struct workqueue_struct *cache_flush_workqueue;

static int cache_timeout = 1000;
module_param(cache_timeout, int, S_IRUGO);
MODULE_PARM_DESC(cache_timeout,
	"Timeout (in ms) for cache flush (1000 ms default");

static int debug;
module_param(debug, int, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(debug, "Debug level (0-2)");


/* ------------------- sysfs attributes ---------------------------------- */
struct sm_sysfs_attribute {
	struct device_attribute dev_attr;
	char *data;
	int len;
};

static ssize_t sm_attr_show(struct device *dev, struct device_attribute *attr,
		     char *buf)
{
	struct sm_sysfs_attribute *sm_attr =
		container_of(attr, struct sm_sysfs_attribute, dev_attr);

	strncpy(buf, sm_attr->data, sm_attr->len);
	return sm_attr->len;
}


#define NUM_ATTRIBUTES 1
#define SM_CIS_VENDOR_OFFSET 0x59
static struct attribute_group *sm_create_sysfs_attributes(struct sm_ftl *ftl)
{
	struct attribute_group *attr_group;
	struct attribute **attributes;
	struct sm_sysfs_attribute *vendor_attribute;
	char *vendor;

	vendor = kstrndup(ftl->cis_buffer + SM_CIS_VENDOR_OFFSET,
			  SM_SMALL_PAGE - SM_CIS_VENDOR_OFFSET, GFP_KERNEL);
	if (!vendor)
		goto error1;

	/* Initialize sysfs attributes */
	vendor_attribute =
		kzalloc(sizeof(struct sm_sysfs_attribute), GFP_KERNEL);
	if (!vendor_attribute)
		goto error2;

	sysfs_attr_init(&vendor_attribute->dev_attr.attr);

	vendor_attribute->data = vendor;
	vendor_attribute->len = strlen(vendor);
	vendor_attribute->dev_attr.attr.name = "vendor";
	vendor_attribute->dev_attr.attr.mode = S_IRUGO;
	vendor_attribute->dev_attr.show = sm_attr_show;


	/* Create array of pointers to the attributes */
	attributes = kcalloc(NUM_ATTRIBUTES + 1, sizeof(struct attribute *),
								GFP_KERNEL);
	if (!attributes)
		goto error3;
	attributes[0] = &vendor_attribute->dev_attr.attr;

	/* Finally create the attribute group */
	attr_group = kzalloc(sizeof(struct attribute_group), GFP_KERNEL);
	if (!attr_group)
		goto error4;
	attr_group->attrs = attributes;
	return attr_group;
error4:
	kfree(attributes);
error3:
	kfree(vendor_attribute);
error2:
	kfree(vendor);
error1:
	return NULL;
}

static void sm_delete_sysfs_attributes(struct sm_ftl *ftl)
{
	struct attribute **attributes = ftl->disk_attributes->attrs;
	int i;

	for (i = 0; attributes[i] ; i++) {

		struct device_attribute *dev_attr = container_of(attributes[i],
			struct device_attribute, attr);

		struct sm_sysfs_attribute *sm_attr =
			container_of(dev_attr,
				struct sm_sysfs_attribute, dev_attr);

		kfree(sm_attr->data);
		kfree(sm_attr);
	}

	kfree(ftl->disk_attributes->attrs);
	kfree(ftl->disk_attributes);
}


/* ----------------------- oob helpers -------------------------------------- */

static int sm_get_lba(uint8_t *lba)
{
	/* check fixed bits */
	if ((lba[0] & 0xF8) != 0x10)
		return -2;

	/* check parity - endianness doesn't matter */
	if (hweight16(*(uint16_t *)lba) & 1)
		return -2;

	return (lba[1] >> 1) | ((lba[0] & 0x07) << 7);
}


/*
 * Read LBA associated with block
 * returns -1, if block is erased
 * returns -2 if error happens
 */
static int sm_read_lba(struct sm_oob *oob)
{
	static const uint32_t erased_pattern[4] = {
		0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF };

	uint16_t lba_test;
	int lba;

	/* First test for erased block */
	if (!memcmp(oob, erased_pattern, SM_OOB_SIZE))
		return -1;

	/* Now check is both copies of the LBA differ too much */
	lba_test = *(uint16_t *)oob->lba_copy1 ^ *(uint16_t*)oob->lba_copy2;
	if (lba_test && !is_power_of_2(lba_test))
		return -2;

	/* And read it */
	lba = sm_get_lba(oob->lba_copy1);

	if (lba == -2)
		lba = sm_get_lba(oob->lba_copy2);

	return lba;
}

static void sm_write_lba(struct sm_oob *oob, uint16_t lba)
{
	uint8_t tmp[2];

	WARN_ON(lba >= 1000);

	tmp[0] = 0x10 | ((lba >> 7) & 0x07);
	tmp[1] = (lba << 1) & 0xFF;

	if (hweight16(*(uint16_t *)tmp) & 0x01)
		tmp[1] |= 1;

	oob->lba_copy1[0] = oob->lba_copy2[0] = tmp[0];
	oob->lba_copy1[1] = oob->lba_copy2[1] = tmp[1];
}


/* Make offset from parts */
static loff_t sm_mkoffset(struct sm_ftl *ftl, int zone, int block, int boffset)
{
	WARN_ON(boffset & (SM_SECTOR_SIZE - 1));
	WARN_ON(zone < 0 || zone >= ftl->zone_count);
	WARN_ON(block >= ftl->zone_size);
	WARN_ON(boffset >= ftl->block_size);

	if (block == -1)
		return -1;

	return (zone * SM_MAX_ZONE_SIZE + block) * ftl->block_size + boffset;
}

/* Breaks offset into parts */
static void sm_break_offset(struct sm_ftl *ftl, loff_t loffset,
			    int *zone, int *block, int *boffset)
{
	u64 offset = loffset;
	*boffset = do_div(offset, ftl->block_size);
	*block = do_div(offset, ftl->max_lba);
	*zone = offset >= ftl->zone_count ? -1 : offset;
}

/* ---------------------- low level IO ------------------------------------- */

static int sm_correct_sector(uint8_t *buffer, struct sm_oob *oob)
{
	bool sm_order = IS_ENABLED(CONFIG_MTD_NAND_ECC_SW_HAMMING_SMC);
	uint8_t ecc[3];

	ecc_sw_hamming_calculate(buffer, SM_SMALL_PAGE, ecc, sm_order);
	if (ecc_sw_hamming_correct(buffer, ecc, oob->ecc1, SM_SMALL_PAGE,
				   sm_order) < 0)
		return -EIO;

	buffer += SM_SMALL_PAGE;

	ecc_sw_hamming_calculate(buffer, SM_SMALL_PAGE, ecc, sm_order);
	if (ecc_sw_hamming_correct(buffer, ecc, oob->ecc2, SM_SMALL_PAGE,
				   sm_order) < 0)
		return -EIO;
	return 0;
}

/* Reads a sector + oob*/
static int sm_read_sector(struct sm_ftl *ftl,
			  int zone, int block, int boffset,
			  uint8_t *buffer, struct sm_oob *oob)
{
	struct mtd_info *mtd = ftl->trans->mtd;
	struct mtd_oob_ops ops;
	struct sm_oob tmp_oob;
	int ret = -EIO;
	int try = 0;

	/* FTL can contain -1 entries that are by default filled with bits */
	if (block == -1) {
		if (buffer)
			memset(buffer, 0xFF, SM_SECTOR_SIZE);
		return 0;
	}

	/* User might not need the oob, but we do for data verification */
	if (!oob)
		oob = &tmp_oob;

	ops.mode = ftl->smallpagenand ? MTD_OPS_RAW : MTD_OPS_PLACE_OOB;
	ops.ooboffs = 0;
	ops.ooblen = SM_OOB_SIZE;
	ops.oobbuf = (void *)oob;
	ops.len = SM_SECTOR_SIZE;
	ops.datbuf = buffer;

again:
	if (try++) {
		/* Avoid infinite recursion on CIS reads, sm_recheck_media
		 * won't help anyway
		 */
		if (zone == 0 && block == ftl->cis_block && boffset ==
			ftl->cis_boffset)
			return ret;

		/* Test if media is stable */
		if (try == 3 || sm_recheck_media(ftl))
			return ret;
	}

	/* Unfortunately, oob read will _always_ succeed,
	 * despite card removal.....
	 */
	ret = mtd_read_oob(mtd, sm_mkoffset(ftl, zone, block, boffset), &ops);

	/* Test for unknown errors */
	if (ret != 0 && !mtd_is_bitflip_or_eccerr(ret)) {
		dbg("read of block %d at zone %d, failed due to error (%d)",
			block, zone, ret);
		goto again;
	}

	/* Do a basic test on the oob, to guard against returned garbage */
	if (oob->reserved != 0xFFFFFFFF && !is_power_of_2(~oob->reserved))
		goto again;

	/* This should never happen, unless there is a bug in the mtd driver */
	WARN_ON(ops.oobretlen != SM_OOB_SIZE);
	WARN_ON(buffer && ops.retlen != SM_SECTOR_SIZE);

	if (!buffer)
		return 0;

	/* Test if sector marked as bad */
	if (!sm_sector_valid(oob)) {
		dbg("read of block %d at zone %d, failed because it is marked"
			" as bad" , block, zone);
		goto again;
	}

	/* Test ECC*/
	if (mtd_is_eccerr(ret) ||
		(ftl->smallpagenand && sm_correct_sector(buffer, oob))) {

		dbg("read of block %d at zone %d, failed due to ECC error",
			block, zone);
		goto again;
	}

	return 0;
}

/* Writes a sector to media */
static int sm_write_sector(struct sm_ftl *ftl,
			   int zone, int block, int boffset,
			   uint8_t *buffer, struct sm_oob *oob)
{
	struct mtd_oob_ops ops;
	struct mtd_info *mtd = ftl->trans->mtd;
	int ret;

	BUG_ON(ftl->readonly);

	if (zone == 0 && (block == ftl->cis_block || block == 0)) {
		dbg("attempted to write the CIS!");
		return -EIO;
	}

	if (ftl->unstable)
		return -EIO;

	ops.mode = ftl->smallpagenand ? MTD_OPS_RAW : MTD_OPS_PLACE_OOB;
	ops.len = SM_SECTOR_SIZE;
	ops.datbuf = buffer;
	ops.ooboffs = 0;
	ops.ooblen = SM_OOB_SIZE;
	ops.oobbuf = (void *)oob;

	ret = mtd_write_oob(mtd, sm_mkoffset(ftl, zone, block, boffset), &ops);

	/* Now we assume that hardware will catch write bitflip errors */

	if (ret) {
		dbg("write to block %d at zone %d, failed with error %d",
			block, zone, ret);

		sm_recheck_media(ftl);
		return ret;
	}

	/* This should never happen, unless there is a bug in the driver */
	WARN_ON(ops.oobretlen != SM_OOB_SIZE);
	WARN_ON(buffer && ops.retlen != SM_SECTOR_SIZE);

	return 0;
}

/* ------------------------ block IO ------------------------------------- */

/* Write a block using data and lba, and invalid sector bitmap */
static int sm_write_block(struct sm_ftl *ftl, uint8_t *buf,
			  int zone, int block, int lba,
			  unsigned long invalid_bitmap)
{
	bool sm_order = IS_ENABLED(CONFIG_MTD_NAND_ECC_SW_HAMMING_SMC);
	struct sm_oob oob;
	int boffset;
	int retry = 0;

	/* Initialize the oob with requested values */
	memset(&oob, 0xFF, SM_OOB_SIZE);
	sm_write_lba(&oob, lba);
restart:
	if (ftl->unstable)
		return -EIO;

	for (boffset = 0; boffset < ftl->block_size;
				boffset += SM_SECTOR_SIZE) {

		oob.data_status = 0xFF;

		if (test_bit(boffset / SM_SECTOR_SIZE, &invalid_bitmap)) {

			sm_printk("sector %d of block at LBA %d of zone %d"
				" couldn't be read, marking it as invalid",
				boffset / SM_SECTOR_SIZE, lba, zone);

			oob.data_status = 0;
		}

		if (ftl->smallpagenand) {
			ecc_sw_hamming_calculate(buf + boffset,
						 SM_SMALL_PAGE, oob.ecc1,
						 sm_order);

			ecc_sw_hamming_calculate(buf + boffset + SM_SMALL_PAGE,
						 SM_SMALL_PAGE, oob.ecc2,
						 sm_order);
		}
		if (!sm_write_sector(ftl, zone, block, boffset,
							buf + boffset, &oob))
			continue;

		if (!retry) {

			/* If write fails. try to erase the block */
			/* This is safe, because we never write in blocks
			 * that contain valuable data.
			 * This is intended to repair block that are marked
			 * as erased, but that isn't fully erased
			 */

			if (sm_erase_block(ftl, zone, block, 0))
				return -EIO;

			retry = 1;
			goto restart;
		} else {
			sm_mark_block_bad(ftl, zone, block);
			return -EIO;
		}
	}
	return 0;
}


/* Mark whole block at offset 'offs' as bad. */
static void sm_mark_block_bad(struct sm_ftl *ftl, int zone, int block)
{
	struct sm_oob oob;
	int boffset;

	memset(&oob, 0xFF, SM_OOB_SIZE);
	oob.block_status = 0xF0;

	if (ftl->unstable)
		return;

	if (sm_recheck_media(ftl))
		return;

	sm_printk("marking block %d of zone %d as bad", block, zone);

	/* We aren't checking the return value, because we don't care */
	/* This also fails on fake xD cards, but I guess these won't expose
	 * any bad blocks till fail completely
	 */
	for (boffset = 0; boffset < ftl->block_size; boffset += SM_SECTOR_SIZE)
		sm_write_sector(ftl, zone, block, boffset, NULL, &oob);
}

/*
 * Erase a block within a zone
 * If erase succeeds, it updates free block fifo, otherwise marks block as bad
 */
static int sm_erase_block(struct sm_ftl *ftl, int zone_num, uint16_t block,
			  int put_free)
{
	struct ftl_zone *zone = &ftl->zones[zone_num];
	struct mtd_info *mtd = ftl->trans->mtd;
	struct erase_info erase;

	erase.addr = sm_mkoffset(ftl, zone_num, block, 0);
	erase.len = ftl->block_size;

	if (ftl->unstable)
		return -EIO;

	BUG_ON(ftl->readonly);

	if (zone_num == 0 && (block == ftl->cis_block || block == 0)) {
		sm_printk("attempted to erase the CIS!");
		return -EIO;
	}

	if (mtd_erase(mtd, &erase)) {
		sm_printk("erase of block %d in zone %d failed",
							block, zone_num);
		goto error;
	}

	if (put_free)
		kfifo_in(&zone->free_sectors,
			(const unsigned char *)&block, sizeof(block));

	return 0;
error:
	sm_mark_block_bad(ftl, zone_num, block);
	return -EIO;
}

/* Thoroughly test that block is valid. */
static int sm_check_block(struct sm_ftl *ftl, int zone, int block)
{
	int boffset;
	struct sm_oob oob;
	int lbas[] = { -3, 0, 0, 0 };
	int i = 0;
	int test_lba;


	/* First just check that block doesn't look fishy */
	/* Only blocks that are valid or are sliced in two parts, are
	 * accepted
	 */
	for (boffset = 0; boffset < ftl->block_size;
					boffset += SM_SECTOR_SIZE) {

		/* This shouldn't happen anyway */
		if (sm_read_sector(ftl, zone, block, boffset, NULL, &oob))
			return -2;

		test_lba = sm_read_lba(&oob);

		if (lbas[i] != test_lba)
			lbas[++i] = test_lba;

		/* If we found three different LBAs, something is fishy */
		if (i == 3)
			return -EIO;
	}

	/* If the block is sliced (partially erased usually) erase it */
	if (i == 2) {
		sm_erase_block(ftl, zone, block, 1);
		return 1;
	}

	return 0;
}

/* ----------------- media scanning --------------------------------- */
static const struct chs_entry chs_table[] = {
	{ 1,    125,  4,  4  },
	{ 2,    125,  4,  8  },
	{ 4,    250,  4,  8  },
	{ 8,    250,  4,  16 },
	{ 16,   500,  4,  16 },
	{ 32,   500,  8,  16 },
	{ 64,   500,  8,  32 },
	{ 128,  500,  16, 32 },
	{ 256,  1000, 16, 32 },
	{ 512,  1015, 32, 63 },
	{ 1024, 985,  33, 63 },
	{ 2048, 985,  33, 63 },
	{ 0 },
};


static const uint8_t cis_signature[] = {
	0x01, 0x03, 0xD9, 0x01, 0xFF, 0x18, 0x02, 0xDF, 0x01, 0x20
};
/* Find out media parameters.
 * This ideally has to be based on nand id, but for now device size is enough
 */
static int sm_get_media_info(struct sm_ftl *ftl, struct mtd_info *mtd)
{
	int i;
	int size_in_megs = mtd->size / (1024 * 1024);

	ftl->readonly = mtd->type == MTD_ROM;

	/* Manual settings for very old devices */
	ftl->zone_count = 1;
	ftl->smallpagenand = 0;

	switch (size_in_megs) {
	case 1:
		/* 1 MiB flash/rom SmartMedia card (256 byte pages)*/
		ftl->zone_size = 256;
		ftl->max_lba = 250;
		ftl->block_size = 8 * SM_SECTOR_SIZE;
		ftl->smallpagenand = 1;

		break;
	case 2:
		/* 2 MiB flash SmartMedia (256 byte pages)*/
		if (mtd->writesize == SM_SMALL_PAGE) {
			ftl->zone_size = 512;
			ftl->max_lba = 500;
			ftl->block_size = 8 * SM_SECTOR_SIZE;
			ftl->smallpagenand = 1;
		/* 2 MiB rom SmartMedia */
		} else {

			if (!ftl->readonly)
				return -ENODEV;

			ftl->zone_size = 256;
			ftl->max_lba = 250;
			ftl->block_size = 16 * SM_SECTOR_SIZE;
		}
		break;
	case 4:
		/* 4 MiB flash/rom SmartMedia device */
		ftl->zone_size = 512;
		ftl->max_lba = 500;
		ftl->block_size = 16 * SM_SECTOR_SIZE;
		break;
	case 8:
		/* 8 MiB flash/rom SmartMedia device */
		ftl->zone_size = 1024;
		ftl->max_lba = 1000;
		ftl->block_size = 16 * SM_SECTOR_SIZE;
	}

	/* Minimum xD size is 16MiB. Also, all xD cards have standard zone
	 * sizes. SmartMedia cards exist up to 128 MiB and have same layout
	 */
	if (size_in_megs >= 16) {
		ftl->zone_count = size_in_megs / 16;
		ftl->zone_size = 1024;
		ftl->max_lba = 1000;
		ftl->block_size = 32 * SM_SECTOR_SIZE;
	}

	/* Test for proper write,erase and oob sizes */
	if (mtd->erasesize > ftl->block_size)
		return -ENODEV;

	if (mtd->writesize > SM_SECTOR_SIZE)
		return -ENODEV;

	if (ftl->smallpagenand && mtd->oobsize < SM_SMALL_OOB_SIZE)
		return -ENODEV;

	if (!ftl->smallpagenand && mtd->oobsize < SM_OOB_SIZE)
		return -ENODEV;

	/* We use OOB */
	if (!mtd_has_oob(mtd))
		return -ENODEV;

	/* Find geometry information */
	for (i = 0 ; i < ARRAY_SIZE(chs_table) ; i++) {
		if (chs_table[i].size == size_in_megs) {
			ftl->cylinders = chs_table[i].cyl;
			ftl->heads = chs_table[i].head;
			ftl->sectors = chs_table[i].sec;
			return 0;
		}
	}

	sm_printk("media has unknown size : %dMiB", size_in_megs);
	ftl->cylinders = 985;
	ftl->heads =  33;
	ftl->sectors = 63;
	return 0;
}

/* Validate the CIS */
static int sm_read_cis(struct sm_ftl *ftl)
{
	struct sm_oob oob;

	if (sm_read_sector(ftl,
		0, ftl->cis_block, ftl->cis_boffset, ftl->cis_buffer, &oob))
			return -EIO;

	if (!sm_sector_valid(&oob) || !sm_block_valid(&oob))
		return -EIO;

	if (!memcmp(ftl->cis_buffer + ftl->cis_page_offset,
			cis_signature, sizeof(cis_signature))) {
		return 0;
	}

	return -EIO;
}

/* Scan the media for the CIS */
static int sm_find_cis(struct sm_ftl *ftl)
{
	struct sm_oob oob;
	int block, boffset;
	int block_found = 0;
	int cis_found = 0;

	/* Search for first valid block */
	for (block = 0 ; block < ftl->zone_size - ftl->max_lba ; block++) {

		if (sm_read_sector(ftl, 0, block, 0, NULL, &oob))
			continue;

		if (!sm_block_valid(&oob))
			continue;
		block_found = 1;
		break;
	}

	if (!block_found)
		return -EIO;

	/* Search for first valid sector in this block */
	for (boffset = 0 ; boffset < ftl->block_size;
						boffset += SM_SECTOR_SIZE) {

		if (sm_read_sector(ftl, 0, block, boffset, NULL, &oob))
			continue;

		if (!sm_sector_valid(&oob))
			continue;
		break;
	}

	if (boffset == ftl->block_size)
		return -EIO;

	ftl->cis_block = block;
	ftl->cis_boffset = boffset;
	ftl->cis_page_offset = 0;

	cis_found = !sm_read_cis(ftl);

	if (!cis_found) {
		ftl->cis_page_offset = SM_SMALL_PAGE;
		cis_found = !sm_read_cis(ftl);
	}

	if (cis_found) {
		dbg("CIS block found at offset %x",
			block * ftl->block_size +
				boffset + ftl->cis_page_offset);
		return 0;
	}
	return -EIO;
}

/* Basic test to determine if underlying mtd device if functional */
static int sm_recheck_media(struct sm_ftl *ftl)
{
	if (sm_read_cis(ftl)) {

		if (!ftl->unstable) {
			sm_printk("media unstable, not allowing writes");
			ftl->unstable = 1;
		}
		return -EIO;
	}
	return 0;
}

/* Initialize a FTL zone */
static int sm_init_zone(struct sm_ftl *ftl, int zone_num)
{
	struct ftl_zone *zone = &ftl->zones[zone_num];
	struct sm_oob oob;
	uint16_t block;
	int lba;
	int i = 0;
	int len;

	dbg("initializing zone %d", zone_num);

	/* Allocate memory for FTL table */
	zone->lba_to_phys_table = kmalloc_array(ftl->max_lba, 2, GFP_KERNEL);

	if (!zone->lba_to_phys_table)
		return -ENOMEM;
	memset(zone->lba_to_phys_table, -1, ftl->max_lba * 2);


	/* Allocate memory for free sectors FIFO */
	if (kfifo_alloc(&zone->free_sectors, ftl->zone_size * 2, GFP_KERNEL)) {
		kfree(zone->lba_to_phys_table);
		return -ENOMEM;
	}

	/* Now scan the zone */
	for (block = 0 ; block < ftl->zone_size ; block++) {

		/* Skip blocks till the CIS (including) */
		if (zone_num == 0 && block <= ftl->cis_block)
			continue;

		/* Read the oob of first sector */
		if (sm_read_sector(ftl, zone_num, block, 0, NULL, &oob)) {
			kfifo_free(&zone->free_sectors);
			kfree(zone->lba_to_phys_table);
			return -EIO;
		}

		/* Test to see if block is erased. It is enough to test
		 * first sector, because erase happens in one shot
		 */
		if (sm_block_erased(&oob)) {
			kfifo_in(&zone->free_sectors,
				(unsigned char *)&block, 2);
			continue;
		}

		/* If block is marked as bad, skip it */
		/* This assumes we can trust first sector*/
		/* However the way the block valid status is defined, ensures
		 * very low probability of failure here
		 */
		if (!sm_block_valid(&oob)) {
			dbg("PH %04d <-> <marked bad>", block);
			continue;
		}


		lba = sm_read_lba(&oob);

		/* Invalid LBA means that block is damaged. */
		/* We can try to erase it, or mark it as bad, but
		 * lets leave that to recovery application
		 */
		if (lba == -2 || lba >= ftl->max_lba) {
			dbg("PH %04d <-> LBA %04d(bad)", block, lba);
			continue;
		}


		/* If there is no collision,
		 * just put the sector in the FTL table
		 */
		if (zone->lba_to_phys_table[lba] < 0) {
			dbg_verbose("PH %04d <-> LBA %04d", block, lba);
			zone->lba_to_phys_table[lba] = block;
			continue;
		}

		sm_printk("collision"
			" of LBA %d between blocks %d and %d in zone %d",
			lba, zone->lba_to_phys_table[lba], block, zone_num);

		/* Test that this block is valid*/
		if (sm_check_block(ftl, zone_num, block))
			continue;

		/* Test now the old block */
		if (sm_check_block(ftl, zone_num,
					zone->lba_to_phys_table[lba])) {
			zone->lba_to_phys_table[lba] = block;
			continue;
		}

		/* If both blocks are valid and share same LBA, it means that
		 * they hold different versions of same data. It not
		 * known which is more recent, thus just erase one of them
		 */
		sm_printk("both blocks are valid, erasing the later");
		sm_erase_block(ftl, zone_num, block, 1);
	}

	dbg("zone initialized");
	zone->initialized = 1;

	/* No free sectors, means that the zone is heavily damaged, write won't
	 * work, but it can still can be (partially) read
	 */
	if (!kfifo_len(&zone->free_sectors)) {
		sm_printk("no free blocks in zone %d", zone_num);
		return 0;
	}

	/* Randomize first block we write to */
	get_random_bytes(&i, 2);
	i %= (kfifo_len(&zone->free_sectors) / 2);

	while (i--) {
		len = kfifo_out(&zone->free_sectors,
					(unsigned char *)&block, 2);
		WARN_ON(len != 2);
		kfifo_in(&zone->free_sectors, (const unsigned char *)&block, 2);
	}
	return 0;
}

/* Get and automatically initialize an FTL mapping for one zone */
static struct ftl_zone *sm_get_zone(struct sm_ftl *ftl, int zone_num)
{
	struct ftl_zone *zone;
	int error;

	BUG_ON(zone_num >= ftl->zone_count);
	zone = &ftl->zones[zone_num];

	if (!zone->initialized) {
		error = sm_init_zone(ftl, zone_num);

		if (error)
			return ERR_PTR(error);
	}
	return zone;
}


/* ----------------- cache handling ------------------------------------------*/

/* Initialize the one block cache */
static void sm_cache_init(struct sm_ftl *ftl)
{
	ftl->cache_data_invalid_bitmap = 0xFFFFFFFF;
	ftl->cache_clean = 1;
	ftl->cache_zone = -1;
	ftl->cache_block = -1;
	/*memset(ftl->cache_data, 0xAA, ftl->block_size);*/
}

/* Put sector in one block cache */
static void sm_cache_put(struct sm_ftl *ftl, char *buffer, int boffset)
{
	memcpy(ftl->cache_data + boffset, buffer, SM_SECTOR_SIZE);
	clear_bit(boffset / SM_SECTOR_SIZE, &ftl->cache_data_invalid_bitmap);
	ftl->cache_clean = 0;
}

/* Read a sector from the cache */
static int sm_cache_get(struct sm_ftl *ftl, char *buffer, int boffset)
{
	if (test_bit(boffset / SM_SECTOR_SIZE,
		&ftl->cache_data_invalid_bitmap))
			return -1;

	memcpy(buffer, ftl->cache_data + boffset, SM_SECTOR_SIZE);
	return 0;
}

/* Write the cache to hardware */
static int sm_cache_flush(struct sm_ftl *ftl)
{
	struct ftl_zone *zone;

	int sector_num;
	uint16_t write_sector;
	int zone_num = ftl->cache_zone;
	int block_num;

	if (ftl->cache_clean)
		return 0;

	if (ftl->unstable)
		return -EIO;

	BUG_ON(zone_num < 0);
	zone = &ftl->zones[zone_num];
	block_num = zone->lba_to_phys_table[ftl->cache_block];


	/* Try to read all unread areas of the cache block*/
	for_each_set_bit(sector_num, &ftl->cache_data_invalid_bitmap,
		ftl->block_size / SM_SECTOR_SIZE) {

		if (!sm_read_sector(ftl,
			zone_num, block_num, sector_num * SM_SECTOR_SIZE,
			ftl->cache_data + sector_num * SM_SECTOR_SIZE, NULL))
				clear_bit(sector_num,
					&ftl->cache_data_invalid_bitmap);
	}
restart:

	if (ftl->unstable)
		return -EIO;

	/* If there are no spare blocks, */
	/* we could still continue by erasing/writing the current block,
	 * but for such worn out media it doesn't worth the trouble,
	 * and the dangers
	 */
	if (kfifo_out(&zone->free_sectors,
				(unsigned char *)&write_sector, 2) != 2) {
		dbg("no free sectors for write!");
		return -EIO;
	}


	if (sm_write_block(ftl, ftl->cache_data, zone_num, write_sector,
		ftl->cache_block, ftl->cache_data_invalid_bitmap))
			goto restart;

	/* Update the FTL table */
	zone->lba_to_phys_table[ftl->cache_block] = write_sector;

	/* Write succesfull, so erase and free the old block */
	if (block_num > 0)
		sm_erase_block(ftl, zone_num, block_num, 1);

	sm_cache_init(ftl);
	return 0;
}


/* flush timer, runs a second after last write */
static void sm_cache_flush_timer(struct timer_list *t)
{
	struct sm_ftl *ftl = from_timer(ftl, t, timer);
	queue_work(cache_flush_workqueue, &ftl->flush_work);
}

/* cache flush work, kicked by timer */
static void sm_cache_flush_work(struct work_struct *work)
{
	struct sm_ftl *ftl = container_of(work, struct sm_ftl, flush_work);
	mutex_lock(&ftl->mutex);
	sm_cache_flush(ftl);
	mutex_unlock(&ftl->mutex);
	return;
}

/* ---------------- outside interface -------------------------------------- */

/* outside interface: read a sector */
static int sm_read(struct mtd_blktrans_dev *dev,
		   unsigned long sect_no, char *buf)
{
	struct sm_ftl *ftl = dev->priv;
	struct ftl_zone *zone;
	int error = 0, in_cache = 0;
	int zone_num, block, boffset;

	sm_break_offset(ftl, sect_no << 9, &zone_num, &block, &boffset);
	mutex_lock(&ftl->mutex);


	zone = sm_get_zone(ftl, zone_num);
	if (IS_ERR(zone)) {
		error = PTR_ERR(zone);
		goto unlock;
	}

	/* Have to look at cache first */
	if (ftl->cache_zone == zone_num && ftl->cache_block == block) {
		in_cache = 1;
		if (!sm_cache_get(ftl, buf, boffset))
			goto unlock;
	}

	/* Translate the block and return if doesn't exist in the table */
	block = zone->lba_to_phys_table[block];

	if (block == -1) {
		memset(buf, 0xFF, SM_SECTOR_SIZE);
		goto unlock;
	}

	if (sm_read_sector(ftl, zone_num, block, boffset, buf, NULL)) {
		error = -EIO;
		goto unlock;
	}

	if (in_cache)
		sm_cache_put(ftl, buf, boffset);
unlock:
	mutex_unlock(&ftl->mutex);
	return error;
}

/* outside interface: write a sector */
static int sm_write(struct mtd_blktrans_dev *dev,
				unsigned long sec_no, char *buf)
{
	struct sm_ftl *ftl = dev->priv;
	struct ftl_zone *zone;
	int error = 0, zone_num, block, boffset;

	BUG_ON(ftl->readonly);
	sm_break_offset(ftl, sec_no << 9, &zone_num, &block, &boffset);

	/* No need in flush thread running now */
	del_timer(&ftl->timer);
	mutex_lock(&ftl->mutex);

	zone = sm_get_zone(ftl, zone_num);
	if (IS_ERR(zone)) {
		error = PTR_ERR(zone);
		goto unlock;
	}

	/* If entry is not in cache, flush it */
	if (ftl->cache_block != block || ftl->cache_zone != zone_num) {

		error = sm_cache_flush(ftl);
		if (error)
			goto unlock;

		ftl->cache_block = block;
		ftl->cache_zone = zone_num;
	}

	sm_cache_put(ftl, buf, boffset);
unlock:
	mod_timer(&ftl->timer, jiffies + msecs_to_jiffies(cache_timeout));
	mutex_unlock(&ftl->mutex);
	return error;
}

/* outside interface: flush everything */
static int sm_flush(struct mtd_blktrans_dev *dev)
{
	struct sm_ftl *ftl = dev->priv;
	int retval;

	mutex_lock(&ftl->mutex);
	retval =  sm_cache_flush(ftl);
	mutex_unlock(&ftl->mutex);
	return retval;
}

/* outside interface: device is released */
static void sm_release(struct mtd_blktrans_dev *dev)
{
	struct sm_ftl *ftl = dev->priv;

	mutex_lock(&ftl->mutex);
	del_timer_sync(&ftl->timer);
	cancel_work_sync(&ftl->flush_work);
	sm_cache_flush(ftl);
	mutex_unlock(&ftl->mutex);
}

/* outside interface: get geometry */
static int sm_getgeo(struct mtd_blktrans_dev *dev, struct hd_geometry *geo)
{
	struct sm_ftl *ftl = dev->priv;
	geo->heads = ftl->heads;
	geo->sectors = ftl->sectors;
	geo->cylinders = ftl->cylinders;
	return 0;
}

/* external interface: main initialization function */
static void sm_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
{
	struct mtd_blktrans_dev *trans;
	struct sm_ftl *ftl;

	/* Allocate & initialize our private structure */
	ftl = kzalloc(sizeof(struct sm_ftl), GFP_KERNEL);
	if (!ftl)
		goto error1;


	mutex_init(&ftl->mutex);
	timer_setup(&ftl->timer, sm_cache_flush_timer, 0);
	INIT_WORK(&ftl->flush_work, sm_cache_flush_work);

	/* Read media information */
	if (sm_get_media_info(ftl, mtd)) {
		dbg("found unsupported mtd device, aborting");
		goto error2;
	}


	/* Allocate temporary CIS buffer for read retry support */
	ftl->cis_buffer = kzalloc(SM_SECTOR_SIZE, GFP_KERNEL);
	if (!ftl->cis_buffer)
		goto error2;

	/* Allocate zone array, it will be initialized on demand */
	ftl->zones = kcalloc(ftl->zone_count, sizeof(struct ftl_zone),
								GFP_KERNEL);
	if (!ftl->zones)
		goto error3;

	/* Allocate the cache*/
	ftl->cache_data = kzalloc(ftl->block_size, GFP_KERNEL);

	if (!ftl->cache_data)
		goto error4;

	sm_cache_init(ftl);


	/* Allocate upper layer structure and initialize it */
	trans = kzalloc(sizeof(struct mtd_blktrans_dev), GFP_KERNEL);
	if (!trans)
		goto error5;

	ftl->trans = trans;
	trans->priv = ftl;

	trans->tr = tr;
	trans->mtd = mtd;
	trans->devnum = -1;
	trans->size = (ftl->block_size * ftl->max_lba * ftl->zone_count) >> 9;
	trans->readonly = ftl->readonly;

	if (sm_find_cis(ftl)) {
		dbg("CIS not found on mtd device, aborting");
		goto error6;
	}

	ftl->disk_attributes = sm_create_sysfs_attributes(ftl);
	if (!ftl->disk_attributes)
		goto error6;
	trans->disk_attributes = ftl->disk_attributes;

	sm_printk("Found %d MiB xD/SmartMedia FTL on mtd%d",
		(int)(mtd->size / (1024 * 1024)), mtd->index);

	dbg("FTL layout:");
	dbg("%d zone(s), each consists of %d blocks (+%d spares)",
		ftl->zone_count, ftl->max_lba,
		ftl->zone_size - ftl->max_lba);
	dbg("each block consists of %d bytes",
		ftl->block_size);


	/* Register device*/
	if (add_mtd_blktrans_dev(trans)) {
		dbg("error in mtdblktrans layer");
		goto error6;
	}
	return;
error6:
	kfree(trans);
error5:
	kfree(ftl->cache_data);
error4:
	kfree(ftl->zones);
error3:
	kfree(ftl->cis_buffer);
error2:
	kfree(ftl);
error1:
	return;
}

/* main interface: device {surprise,} removal */
static void sm_remove_dev(struct mtd_blktrans_dev *dev)
{
	struct sm_ftl *ftl = dev->priv;
	int i;

	del_mtd_blktrans_dev(dev);
	ftl->trans = NULL;

	for (i = 0 ; i < ftl->zone_count; i++) {

		if (!ftl->zones[i].initialized)
			continue;

		kfree(ftl->zones[i].lba_to_phys_table);
		kfifo_free(&ftl->zones[i].free_sectors);
	}

	sm_delete_sysfs_attributes(ftl);
	kfree(ftl->cis_buffer);
	kfree(ftl->zones);
	kfree(ftl->cache_data);
	kfree(ftl);
}

static struct mtd_blktrans_ops sm_ftl_ops = {
	.name		= "smblk",
	.major		= 0,
	.part_bits	= SM_FTL_PARTN_BITS,
	.blksize	= SM_SECTOR_SIZE,
	.getgeo		= sm_getgeo,

	.add_mtd	= sm_add_mtd,
	.remove_dev	= sm_remove_dev,

	.readsect	= sm_read,
	.writesect	= sm_write,

	.flush		= sm_flush,
	.release	= sm_release,

	.owner		= THIS_MODULE,
};

static __init int sm_module_init(void)
{
	int error = 0;

	cache_flush_workqueue = create_freezable_workqueue("smflush");
	if (!cache_flush_workqueue)
		return -ENOMEM;

	error = register_mtd_blktrans(&sm_ftl_ops);
	if (error)
		destroy_workqueue(cache_flush_workqueue);
	return error;

}

static void __exit sm_module_exit(void)
{
	destroy_workqueue(cache_flush_workqueue);
	deregister_mtd_blktrans(&sm_ftl_ops);
}

module_init(sm_module_init);
module_exit(sm_module_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Maxim Levitsky <maximlevitsky@gmail.com>");
MODULE_DESCRIPTION("Smartmedia/xD mtd translation layer");