drivers/mtd/nand/ecc-sw-bch.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * This file provides ECC correction for more than 1 bit per block of data,
  * using binary BCH codes. It relies on the generic BCH library lib/bch.c.
  *
  * Copyright © 2011 Ivan Djelic <ivan.djelic@parrot.com>
  */

 #include <linux/types.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/bitops.h>
 #include <linux/mtd/nand.h>
 #include <linux/mtd/nand-ecc-sw-bch.h>

 /**
  * nand_ecc_sw_bch_calculate - Calculate the ECC corresponding to a data block
  * @nand: NAND device
  * @buf: Input buffer with raw data
  * @code: Output buffer with ECC
  */
 int nand_ecc_sw_bch_calculate(struct nand_device *nand,
 			      const unsigned char *buf, unsigned char *code)
 {
 	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
 	unsigned int i;

 	memset(code, 0, engine_conf->code_size);
 	bch_encode(engine_conf->bch, buf, nand->ecc.ctx.conf.step_size, code);

 	/* apply mask so that an erased page is a valid codeword */
 	for (i = 0; i < engine_conf->code_size; i++)
 		code[i] ^= engine_conf->eccmask[i];

 	return 0;
 }
 EXPORT_SYMBOL(nand_ecc_sw_bch_calculate);

 /**
  * nand_ecc_sw_bch_correct - Detect, correct and report bit error(s)
  * @nand: NAND device
  * @buf: Raw data read from the chip
  * @read_ecc: ECC bytes from the chip
  * @calc_ecc: ECC calculated from the raw data
  *
  * Detect and correct bit errors for a data block.
  */
 int nand_ecc_sw_bch_correct(struct nand_device *nand, unsigned char *buf,
 			    unsigned char *read_ecc, unsigned char *calc_ecc)
 {
 	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
 	unsigned int step_size = nand->ecc.ctx.conf.step_size;
 	unsigned int *errloc = engine_conf->errloc;
 	int i, count;

 	count = bch_decode(engine_conf->bch, NULL, step_size, read_ecc,
 			   calc_ecc, NULL, errloc);
 	if (count > 0) {
 		for (i = 0; i < count; i++) {
 			if (errloc[i] < (step_size * 8))
 				/* The error is in the data area: correct it */
 				buf[errloc[i] >> 3] ^= (1 << (errloc[i] & 7));

 			/* Otherwise the error is in the ECC area: nothing to do */
 			pr_debug("%s: corrected bitflip %u\n", __func__,
 				 errloc[i]);
 		}
 	} else if (count < 0) {
 		pr_err("ECC unrecoverable error\n");
 		count = -EBADMSG;
 	}

 	return count;
 }
 EXPORT_SYMBOL(nand_ecc_sw_bch_correct);

 /**
  * nand_ecc_sw_bch_cleanup - Cleanup software BCH ECC resources
  * @nand: NAND device
  */
 static void nand_ecc_sw_bch_cleanup(struct nand_device *nand)
 {
 	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;

 	bch_free(engine_conf->bch);
 	kfree(engine_conf->errloc);
 	kfree(engine_conf->eccmask);
 }

 /**
  * nand_ecc_sw_bch_init - Initialize software BCH ECC engine
  * @nand: NAND device
  *
  * Returns: a pointer to a new NAND BCH control structure, or NULL upon failure
  *
  * Initialize NAND BCH error correction. @nand.ecc parameters 'step_size' and
  * 'bytes' are used to compute the following BCH parameters:
  *     m, the Galois field order
  *     t, the error correction capability
  * 'bytes' should be equal to the number of bytes required to store m * t
  * bits, where m is such that 2^m - 1 > step_size * 8.
  *
  * Example: to configure 4 bit correction per 512 bytes, you should pass
  * step_size = 512 (thus, m = 13 is the smallest integer such that 2^m - 1 > 512 * 8)
  * bytes = 7 (7 bytes are required to store m * t = 13 * 4 = 52 bits)
  */
 static int nand_ecc_sw_bch_init(struct nand_device *nand)
 {
 	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
 	unsigned int eccsize = nand->ecc.ctx.conf.step_size;
 	unsigned int eccbytes = engine_conf->code_size;
 	unsigned int m, t, i;
 	unsigned char *erased_page;
 	int ret;

 	m = fls(1 + (8 * eccsize));
 	t = (eccbytes * 8) / m;

 	engine_conf->bch = bch_init(m, t, 0, false);
 	if (!engine_conf->bch)
 		return -EINVAL;

 	engine_conf->eccmask = kzalloc(eccbytes, GFP_KERNEL);
 	engine_conf->errloc = kmalloc_array(t, sizeof(*engine_conf->errloc),
 					    GFP_KERNEL);
 	if (!engine_conf->eccmask || !engine_conf->errloc) {
 		ret = -ENOMEM;
 		goto cleanup;
 	}

 	/* Compute and store the inverted ECC of an erased step */
 	erased_page = kmalloc(eccsize, GFP_KERNEL);
 	if (!erased_page) {
 		ret = -ENOMEM;
 		goto cleanup;
 	}

 	memset(erased_page, 0xff, eccsize);
 	bch_encode(engine_conf->bch, erased_page, eccsize,
 		   engine_conf->eccmask);
 	kfree(erased_page);

 	for (i = 0; i < eccbytes; i++)
 		engine_conf->eccmask[i] ^= 0xff;

 	/* Verify that the number of code bytes has the expected value */
 	if (engine_conf->bch->ecc_bytes != eccbytes) {
 		pr_err("Invalid number of ECC bytes: %u, expected: %u\n",
 		       eccbytes, engine_conf->bch->ecc_bytes);
 		ret = -EINVAL;
 		goto cleanup;
 	}

 	/* Sanity checks */
 	if (8 * (eccsize + eccbytes) >= (1 << m)) {
 		pr_err("ECC step size is too large (%u)\n", eccsize);
 		ret = -EINVAL;
 		goto cleanup;
 	}

 	return 0;

 cleanup:
 	nand_ecc_sw_bch_cleanup(nand);

 	return ret;
 }

 int nand_ecc_sw_bch_init_ctx(struct nand_device *nand)
 {
 	struct nand_ecc_props *conf = &nand->ecc.ctx.conf;
 	struct mtd_info *mtd = nanddev_to_mtd(nand);
 	struct nand_ecc_sw_bch_conf *engine_conf;
 	unsigned int code_size = 0, nsteps;
 	int ret;

 	/* Only large page NAND chips may use BCH */
 	if (mtd->oobsize < 64) {
 		pr_err("BCH cannot be used with small page NAND chips\n");
 		return -EINVAL;
 	}

 	if (!mtd->ooblayout)
 		mtd_set_ooblayout(mtd, nand_get_large_page_ooblayout());

 	conf->engine_type = NAND_ECC_ENGINE_TYPE_SOFT;
 	conf->algo = NAND_ECC_ALGO_BCH;
 	conf->step_size = nand->ecc.user_conf.step_size;
 	conf->strength = nand->ecc.user_conf.strength;

 	/*
 	 * Board driver should supply ECC size and ECC strength
 	 * values to select how many bits are correctable.
 	 * Otherwise, default to 512 bytes for large page devices and 256 for
 	 * small page devices.
 	 */
 	if (!conf->step_size) {
 		if (mtd->oobsize >= 64)
 			conf->step_size = 512;
 		else
 			conf->step_size = 256;

 		conf->strength = 4;
 	}

 	nsteps = mtd->writesize / conf->step_size;

 	/* Maximize */
 	if (nand->ecc.user_conf.flags & NAND_ECC_MAXIMIZE_STRENGTH) {
 		conf->step_size = 1024;
 		nsteps = mtd->writesize / conf->step_size;
 		/* Reserve 2 bytes for the BBM */
 		code_size = (mtd->oobsize - 2) / nsteps;
 		conf->strength = code_size * 8 / fls(8 * conf->step_size);
 	}

 	if (!code_size)
 		code_size = DIV_ROUND_UP(conf->strength *
 					 fls(8 * conf->step_size), 8);

 	if (!conf->strength)
 		conf->strength = (code_size * 8) / fls(8 * conf->step_size);

 	if (!code_size && !conf->strength) {
 		pr_err("Missing ECC parameters\n");
 		return -EINVAL;
 	}

 	engine_conf = kzalloc(sizeof(*engine_conf), GFP_KERNEL);
 	if (!engine_conf)
 		return -ENOMEM;

 	ret = nand_ecc_init_req_tweaking(&engine_conf->req_ctx, nand);
 	if (ret)
 		goto free_engine_conf;

 	engine_conf->code_size = code_size;
 	engine_conf->calc_buf = kzalloc(mtd->oobsize, GFP_KERNEL);
 	engine_conf->code_buf = kzalloc(mtd->oobsize, GFP_KERNEL);
 	if (!engine_conf->calc_buf || !engine_conf->code_buf) {
 		ret = -ENOMEM;
 		goto free_bufs;
 	}

 	nand->ecc.ctx.priv = engine_conf;
 	nand->ecc.ctx.nsteps = nsteps;
 	nand->ecc.ctx.total = nsteps * code_size;

 	ret = nand_ecc_sw_bch_init(nand);
 	if (ret)
 		goto free_bufs;

 	/* Verify the layout validity */
 	if (mtd_ooblayout_count_eccbytes(mtd) !=
 	    nand->ecc.ctx.nsteps * engine_conf->code_size) {
 		pr_err("Invalid ECC layout\n");
 		ret = -EINVAL;
 		goto cleanup_bch_ctx;
 	}

 	return 0;

 cleanup_bch_ctx:
 	nand_ecc_sw_bch_cleanup(nand);
 free_bufs:
 	nand_ecc_cleanup_req_tweaking(&engine_conf->req_ctx);
 	kfree(engine_conf->calc_buf);
 	kfree(engine_conf->code_buf);
 free_engine_conf:
 	kfree(engine_conf);

 	return ret;
 }
 EXPORT_SYMBOL(nand_ecc_sw_bch_init_ctx);

 void nand_ecc_sw_bch_cleanup_ctx(struct nand_device *nand)
 {
 	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;

 	if (engine_conf) {
 		nand_ecc_sw_bch_cleanup(nand);
 		nand_ecc_cleanup_req_tweaking(&engine_conf->req_ctx);
 		kfree(engine_conf->calc_buf);
 		kfree(engine_conf->code_buf);
 		kfree(engine_conf);
 	}
 }
 EXPORT_SYMBOL(nand_ecc_sw_bch_cleanup_ctx);

 static int nand_ecc_sw_bch_prepare_io_req(struct nand_device *nand,
 					  struct nand_page_io_req *req)
 {
 	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
 	struct mtd_info *mtd = nanddev_to_mtd(nand);
 	int eccsize = nand->ecc.ctx.conf.step_size;
 	int eccbytes = engine_conf->code_size;
 	int eccsteps = nand->ecc.ctx.nsteps;
 	int total = nand->ecc.ctx.total;
 	u8 *ecccalc = engine_conf->calc_buf;
 	const u8 *data;
 	int i;

 	/* Nothing to do for a raw operation */
 	if (req->mode == MTD_OPS_RAW)
 		return 0;

 	/* This engine does not provide BBM/free OOB bytes protection */
 	if (!req->datalen)
 		return 0;

 	nand_ecc_tweak_req(&engine_conf->req_ctx, req);

 	/* No more preparation for page read */
 	if (req->type == NAND_PAGE_READ)
 		return 0;

 	/* Preparation for page write: derive the ECC bytes and place them */
 	for (i = 0, data = req->databuf.out;
 	     eccsteps;
 	     eccsteps--, i += eccbytes, data += eccsize)
 		nand_ecc_sw_bch_calculate(nand, data, &ecccalc[i]);

 	return mtd_ooblayout_set_eccbytes(mtd, ecccalc, (void *)req->oobbuf.out,
 					  0, total);
 }

 static int nand_ecc_sw_bch_finish_io_req(struct nand_device *nand,
 					 struct nand_page_io_req *req)
 {
 	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
 	struct mtd_info *mtd = nanddev_to_mtd(nand);
 	int eccsize = nand->ecc.ctx.conf.step_size;
 	int total = nand->ecc.ctx.total;
 	int eccbytes = engine_conf->code_size;
 	int eccsteps = nand->ecc.ctx.nsteps;
 	u8 *ecccalc = engine_conf->calc_buf;
 	u8 *ecccode = engine_conf->code_buf;
 	unsigned int max_bitflips = 0;
 	u8 *data = req->databuf.in;
 	int i, ret;

 	/* Nothing to do for a raw operation */
 	if (req->mode == MTD_OPS_RAW)
 		return 0;

 	/* This engine does not provide BBM/free OOB bytes protection */
 	if (!req->datalen)
 		return 0;

 	/* No more preparation for page write */
 	if (req->type == NAND_PAGE_WRITE) {
 		nand_ecc_restore_req(&engine_conf->req_ctx, req);
 		return 0;
 	}

 	/* Finish a page read: retrieve the (raw) ECC bytes*/
 	ret = mtd_ooblayout_get_eccbytes(mtd, ecccode, req->oobbuf.in, 0,
 					 total);
 	if (ret)
 		return ret;

 	/* Calculate the ECC bytes */
 	for (i = 0; eccsteps; eccsteps--, i += eccbytes, data += eccsize)
 		nand_ecc_sw_bch_calculate(nand, data, &ecccalc[i]);

 	/* Finish a page read: compare and correct */
 	for (eccsteps = nand->ecc.ctx.nsteps, i = 0, data = req->databuf.in;
 	     eccsteps;
 	     eccsteps--, i += eccbytes, data += eccsize) {
 		int stat =  nand_ecc_sw_bch_correct(nand, data,
 						    &ecccode[i],
 						    &ecccalc[i]);
 		if (stat < 0) {
 			mtd->ecc_stats.failed++;
 		} else {
 			mtd->ecc_stats.corrected += stat;
 			max_bitflips = max_t(unsigned int, max_bitflips, stat);
 		}
 	}

 	nand_ecc_restore_req(&engine_conf->req_ctx, req);

 	return max_bitflips;
 }

 static struct nand_ecc_engine_ops nand_ecc_sw_bch_engine_ops = {
 	.init_ctx = nand_ecc_sw_bch_init_ctx,
 	.cleanup_ctx = nand_ecc_sw_bch_cleanup_ctx,
 	.prepare_io_req = nand_ecc_sw_bch_prepare_io_req,
 	.finish_io_req = nand_ecc_sw_bch_finish_io_req,
 };

 static struct nand_ecc_engine nand_ecc_sw_bch_engine = {
 	.ops = &nand_ecc_sw_bch_engine_ops,
 };

 struct nand_ecc_engine *nand_ecc_sw_bch_get_engine(void)
 {
 	return &nand_ecc_sw_bch_engine;
 }
 EXPORT_SYMBOL(nand_ecc_sw_bch_get_engine);

 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Ivan Djelic <ivan.djelic@parrot.com>");
 MODULE_DESCRIPTION("NAND software BCH ECC support");
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* This file provides ECC correction for more than 1 bit per block of data,
	* using binary BCH codes. It relies on the generic BCH library lib/bch.c.
	*
	* Copyright © 2011 Ivan Djelic <ivan.djelic@parrot.com>
	*/

	#include <linux/types.h>
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/slab.h>
	#include <linux/bitops.h>
	#include <linux/mtd/nand.h>
	#include <linux/mtd/nand-ecc-sw-bch.h>

	/**
	* nand_ecc_sw_bch_calculate - Calculate the ECC corresponding to a data block
	* @nand: NAND device
	* @buf: Input buffer with raw data
	* @code: Output buffer with ECC
	*/
	int nand_ecc_sw_bch_calculate(struct nand_device *nand,
	const unsigned char buf, unsigned char code)
	{
	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
	unsigned int i;

	memset(code, 0, engine_conf->code_size);
	bch_encode(engine_conf->bch, buf, nand->ecc.ctx.conf.step_size, code);

	/* apply mask so that an erased page is a valid codeword */
	for (i = 0; i < engine_conf->code_size; i++)
	code[i] ^= engine_conf->eccmask[i];

	return 0;
	}
	EXPORT_SYMBOL(nand_ecc_sw_bch_calculate);

	/**
	* nand_ecc_sw_bch_correct - Detect, correct and report bit error(s)
	* @nand: NAND device
	* @buf: Raw data read from the chip
	* @read_ecc: ECC bytes from the chip
	* @calc_ecc: ECC calculated from the raw data
	*
	* Detect and correct bit errors for a data block.
	*/
	int nand_ecc_sw_bch_correct(struct nand_device nand, unsigned char buf,
	unsigned char read_ecc, unsigned char calc_ecc)
	{
	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
	unsigned int step_size = nand->ecc.ctx.conf.step_size;
	unsigned int *errloc = engine_conf->errloc;
	int i, count;

	count = bch_decode(engine_conf->bch, NULL, step_size, read_ecc,
	calc_ecc, NULL, errloc);
	if (count > 0) {
	for (i = 0; i < count; i++) {
	if (errloc[i] < (step_size * 8))
	/* The error is in the data area: correct it */
	buf[errloc[i] >> 3] ^= (1 << (errloc[i] & 7));

	/* Otherwise the error is in the ECC area: nothing to do */
	pr_debug("%s: corrected bitflip %u\n", __func__,
	errloc[i]);
	}
	} else if (count < 0) {
	pr_err("ECC unrecoverable error\n");
	count = -EBADMSG;
	}

	return count;
	}
	EXPORT_SYMBOL(nand_ecc_sw_bch_correct);

	/**
	* nand_ecc_sw_bch_cleanup - Cleanup software BCH ECC resources
	* @nand: NAND device
	*/
	static void nand_ecc_sw_bch_cleanup(struct nand_device *nand)
	{
	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;

	bch_free(engine_conf->bch);
	kfree(engine_conf->errloc);
	kfree(engine_conf->eccmask);
	}

	/**
	* nand_ecc_sw_bch_init - Initialize software BCH ECC engine
	* @nand: NAND device
	*
	* Returns: a pointer to a new NAND BCH control structure, or NULL upon failure
	*
	* Initialize NAND BCH error correction. @nand.ecc parameters 'step_size' and
	* 'bytes' are used to compute the following BCH parameters:
	* m, the Galois field order
	* t, the error correction capability
	* 'bytes' should be equal to the number of bytes required to store m * t
	* bits, where m is such that 2^m - 1 > step_size * 8.
	*
	* Example: to configure 4 bit correction per 512 bytes, you should pass
	* step_size = 512 (thus, m = 13 is the smallest integer such that 2^m - 1 > 512 * 8)
	* bytes = 7 (7 bytes are required to store m * t = 13 * 4 = 52 bits)
	*/
	static int nand_ecc_sw_bch_init(struct nand_device *nand)
	{
	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
	unsigned int eccsize = nand->ecc.ctx.conf.step_size;
	unsigned int eccbytes = engine_conf->code_size;
	unsigned int m, t, i;
	unsigned char *erased_page;
	int ret;

	m = fls(1 + (8 * eccsize));
	t = (eccbytes * 8) / m;

	engine_conf->bch = bch_init(m, t, 0, false);
	if (!engine_conf->bch)
	return -EINVAL;

	engine_conf->eccmask = kzalloc(eccbytes, GFP_KERNEL);
	engine_conf->errloc = kmalloc_array(t, sizeof(*engine_conf->errloc),
	GFP_KERNEL);
	if (!engine_conf->eccmask \|\| !engine_conf->errloc) {
	ret = -ENOMEM;
	goto cleanup;
	}

	/* Compute and store the inverted ECC of an erased step */
	erased_page = kmalloc(eccsize, GFP_KERNEL);
	if (!erased_page) {
	ret = -ENOMEM;
	goto cleanup;
	}

	memset(erased_page, 0xff, eccsize);
	bch_encode(engine_conf->bch, erased_page, eccsize,
	engine_conf->eccmask);
	kfree(erased_page);

	for (i = 0; i < eccbytes; i++)
	engine_conf->eccmask[i] ^= 0xff;

	/* Verify that the number of code bytes has the expected value */
	if (engine_conf->bch->ecc_bytes != eccbytes) {
	pr_err("Invalid number of ECC bytes: %u, expected: %u\n",
	eccbytes, engine_conf->bch->ecc_bytes);
	ret = -EINVAL;
	goto cleanup;
	}

	/* Sanity checks */
	if (8 * (eccsize + eccbytes) >= (1 << m)) {
	pr_err("ECC step size is too large (%u)\n", eccsize);
	ret = -EINVAL;
	goto cleanup;
	}

	return 0;

	cleanup:
	nand_ecc_sw_bch_cleanup(nand);

	return ret;
	}

	int nand_ecc_sw_bch_init_ctx(struct nand_device *nand)
	{
	struct nand_ecc_props *conf = &nand->ecc.ctx.conf;
	struct mtd_info *mtd = nanddev_to_mtd(nand);
	struct nand_ecc_sw_bch_conf *engine_conf;
	unsigned int code_size = 0, nsteps;
	int ret;

	/* Only large page NAND chips may use BCH */
	if (mtd->oobsize < 64) {
	pr_err("BCH cannot be used with small page NAND chips\n");
	return -EINVAL;
	}

	if (!mtd->ooblayout)
	mtd_set_ooblayout(mtd, nand_get_large_page_ooblayout());

	conf->engine_type = NAND_ECC_ENGINE_TYPE_SOFT;
	conf->algo = NAND_ECC_ALGO_BCH;
	conf->step_size = nand->ecc.user_conf.step_size;
	conf->strength = nand->ecc.user_conf.strength;

	/*
	* Board driver should supply ECC size and ECC strength
	* values to select how many bits are correctable.
	* Otherwise, default to 512 bytes for large page devices and 256 for
	* small page devices.
	*/
	if (!conf->step_size) {
	if (mtd->oobsize >= 64)
	conf->step_size = 512;
	else
	conf->step_size = 256;

	conf->strength = 4;
	}

	nsteps = mtd->writesize / conf->step_size;

	/* Maximize */
	if (nand->ecc.user_conf.flags & NAND_ECC_MAXIMIZE_STRENGTH) {
	conf->step_size = 1024;
	nsteps = mtd->writesize / conf->step_size;
	/* Reserve 2 bytes for the BBM */
	code_size = (mtd->oobsize - 2) / nsteps;
	conf->strength = code_size * 8 / fls(8 * conf->step_size);
	}

	if (!code_size)
	code_size = DIV_ROUND_UP(conf->strength *
	fls(8 * conf->step_size), 8);

	if (!conf->strength)
	conf->strength = (code_size * 8) / fls(8 * conf->step_size);

	if (!code_size && !conf->strength) {
	pr_err("Missing ECC parameters\n");
	return -EINVAL;
	}

	engine_conf = kzalloc(sizeof(*engine_conf), GFP_KERNEL);
	if (!engine_conf)
	return -ENOMEM;

	ret = nand_ecc_init_req_tweaking(&engine_conf->req_ctx, nand);
	if (ret)
	goto free_engine_conf;

	engine_conf->code_size = code_size;
	engine_conf->calc_buf = kzalloc(mtd->oobsize, GFP_KERNEL);
	engine_conf->code_buf = kzalloc(mtd->oobsize, GFP_KERNEL);
	if (!engine_conf->calc_buf \|\| !engine_conf->code_buf) {
	ret = -ENOMEM;
	goto free_bufs;
	}

	nand->ecc.ctx.priv = engine_conf;
	nand->ecc.ctx.nsteps = nsteps;
	nand->ecc.ctx.total = nsteps * code_size;

	ret = nand_ecc_sw_bch_init(nand);
	if (ret)
	goto free_bufs;

	/* Verify the layout validity */
	if (mtd_ooblayout_count_eccbytes(mtd) !=
	nand->ecc.ctx.nsteps * engine_conf->code_size) {
	pr_err("Invalid ECC layout\n");
	ret = -EINVAL;
	goto cleanup_bch_ctx;
	}

	return 0;

	cleanup_bch_ctx:
	nand_ecc_sw_bch_cleanup(nand);
	free_bufs:
	nand_ecc_cleanup_req_tweaking(&engine_conf->req_ctx);
	kfree(engine_conf->calc_buf);
	kfree(engine_conf->code_buf);
	free_engine_conf:
	kfree(engine_conf);

	return ret;
	}
	EXPORT_SYMBOL(nand_ecc_sw_bch_init_ctx);

	void nand_ecc_sw_bch_cleanup_ctx(struct nand_device *nand)
	{
	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;

	if (engine_conf) {
	nand_ecc_sw_bch_cleanup(nand);
	nand_ecc_cleanup_req_tweaking(&engine_conf->req_ctx);
	kfree(engine_conf->calc_buf);
	kfree(engine_conf->code_buf);
	kfree(engine_conf);
	}
	}
	EXPORT_SYMBOL(nand_ecc_sw_bch_cleanup_ctx);

	static int nand_ecc_sw_bch_prepare_io_req(struct nand_device *nand,
	struct nand_page_io_req *req)
	{
	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
	struct mtd_info *mtd = nanddev_to_mtd(nand);
	int eccsize = nand->ecc.ctx.conf.step_size;
	int eccbytes = engine_conf->code_size;
	int eccsteps = nand->ecc.ctx.nsteps;
	int total = nand->ecc.ctx.total;
	u8 *ecccalc = engine_conf->calc_buf;
	const u8 *data;
	int i;

	/* Nothing to do for a raw operation */
	if (req->mode == MTD_OPS_RAW)
	return 0;

	/* This engine does not provide BBM/free OOB bytes protection */
	if (!req->datalen)
	return 0;

	nand_ecc_tweak_req(&engine_conf->req_ctx, req);

	/* No more preparation for page read */
	if (req->type == NAND_PAGE_READ)
	return 0;

	/* Preparation for page write: derive the ECC bytes and place them */
	for (i = 0, data = req->databuf.out;
	eccsteps;
	eccsteps--, i += eccbytes, data += eccsize)
	nand_ecc_sw_bch_calculate(nand, data, &ecccalc[i]);

	return mtd_ooblayout_set_eccbytes(mtd, ecccalc, (void *)req->oobbuf.out,
	0, total);
	}

	static int nand_ecc_sw_bch_finish_io_req(struct nand_device *nand,
	struct nand_page_io_req *req)
	{
	struct nand_ecc_sw_bch_conf *engine_conf = nand->ecc.ctx.priv;
	struct mtd_info *mtd = nanddev_to_mtd(nand);
	int eccsize = nand->ecc.ctx.conf.step_size;
	int total = nand->ecc.ctx.total;
	int eccbytes = engine_conf->code_size;
	int eccsteps = nand->ecc.ctx.nsteps;
	u8 *ecccalc = engine_conf->calc_buf;
	u8 *ecccode = engine_conf->code_buf;
	unsigned int max_bitflips = 0;
	u8 *data = req->databuf.in;
	int i, ret;

	/* Nothing to do for a raw operation */
	if (req->mode == MTD_OPS_RAW)
	return 0;

	/* This engine does not provide BBM/free OOB bytes protection */
	if (!req->datalen)
	return 0;

	/* No more preparation for page write */
	if (req->type == NAND_PAGE_WRITE) {
	nand_ecc_restore_req(&engine_conf->req_ctx, req);
	return 0;
	}

	/* Finish a page read: retrieve the (raw) ECC bytes*/
	ret = mtd_ooblayout_get_eccbytes(mtd, ecccode, req->oobbuf.in, 0,
	total);
	if (ret)
	return ret;

	/* Calculate the ECC bytes */
	for (i = 0; eccsteps; eccsteps--, i += eccbytes, data += eccsize)
	nand_ecc_sw_bch_calculate(nand, data, &ecccalc[i]);

	/* Finish a page read: compare and correct */
	for (eccsteps = nand->ecc.ctx.nsteps, i = 0, data = req->databuf.in;
	eccsteps;
	eccsteps--, i += eccbytes, data += eccsize) {
	int stat = nand_ecc_sw_bch_correct(nand, data,
	&ecccode[i],
	&ecccalc[i]);
	if (stat < 0) {
	mtd->ecc_stats.failed++;
	} else {
	mtd->ecc_stats.corrected += stat;
	max_bitflips = max_t(unsigned int, max_bitflips, stat);
	}
	}

	nand_ecc_restore_req(&engine_conf->req_ctx, req);

	return max_bitflips;
	}

	static struct nand_ecc_engine_ops nand_ecc_sw_bch_engine_ops = {
	.init_ctx = nand_ecc_sw_bch_init_ctx,
	.cleanup_ctx = nand_ecc_sw_bch_cleanup_ctx,
	.prepare_io_req = nand_ecc_sw_bch_prepare_io_req,
	.finish_io_req = nand_ecc_sw_bch_finish_io_req,
	};

	static struct nand_ecc_engine nand_ecc_sw_bch_engine = {
	.ops = &nand_ecc_sw_bch_engine_ops,
	};

	struct nand_ecc_engine *nand_ecc_sw_bch_get_engine(void)
	{
	return &nand_ecc_sw_bch_engine;
	}
	EXPORT_SYMBOL(nand_ecc_sw_bch_get_engine);

	MODULE_LICENSE("GPL");
	MODULE_AUTHOR("Ivan Djelic <ivan.djelic@parrot.com>");
	MODULE_DESCRIPTION("NAND software BCH ECC support");