path: root/drivers/mtd/nand/core.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2017 Free Electrons
 *
 * Authors:
 *	Boris Brezillon <boris.brezillon@free-electrons.com>
 *	Peter Pan <peterpandong@micron.com>
 */

#define pr_fmt(fmt)	"nand: " fmt

#include <linux/module.h>
#include <linux/mtd/nand.h>

/**
 * nand_check_erased_buf - check if a buffer contains (almost) only 0xff data
 * @buf: buffer to test
 * @len: buffer length
 * @bitflips_threshold: maximum number of bitflips
 *
 * Check if a buffer contains only 0xff, which means the underlying region
 * has been erased and is ready to be programmed.
 * The bitflips_threshold specify the maximum number of bitflips before
 * considering the region is not erased.
 * Note: The logic of this function has been extracted from the memweight
 * implementation, except that nand_check_erased_buf function exit before
 * testing the whole buffer if the number of bitflips exceed the
 * bitflips_threshold value.
 *
 * Returns a positive number of bitflips less than or equal to
 * bitflips_threshold, or -ERROR_CODE for bitflips in excess of the
 * threshold.
 */
static int nand_check_erased_buf(void *buf, int len, int bitflips_threshold)
{
	const unsigned char *bitmap = buf;
	int bitflips = 0;
	int weight;

	for (; len && ((uintptr_t)bitmap) % sizeof(long);
	     len--, bitmap++) {
		weight = hweight8(*bitmap);
		bitflips += BITS_PER_BYTE - weight;
		if (unlikely(bitflips > bitflips_threshold))
			return -EBADMSG;
	}

	for (; len >= sizeof(long);
	     len -= sizeof(long), bitmap += sizeof(long)) {
		unsigned long d = *((unsigned long *)bitmap);
		if (d == ~0UL)
			continue;
		weight = hweight_long(d);
		bitflips += BITS_PER_LONG - weight;
		if (unlikely(bitflips > bitflips_threshold))
			return -EBADMSG;
	}

	for (; len > 0; len--, bitmap++) {
		weight = hweight8(*bitmap);
		bitflips += BITS_PER_BYTE - weight;
		if (unlikely(bitflips > bitflips_threshold))
			return -EBADMSG;
	}

	return bitflips;
}

/**
 * nand_check_erased_ecc_chunk - check if an ECC chunk contains (almost) only
 *				 0xff data
 * @data: data buffer to test
 * @datalen: data length
 * @ecc: ECC buffer
 * @ecclen: ECC length
 * @extraoob: extra OOB buffer
 * @extraooblen: extra OOB length
 * @bitflips_threshold: maximum number of bitflips
 *
 * Check if a data buffer and its associated ECC and OOB data contains only
 * 0xff pattern, which means the underlying region has been erased and is
 * ready to be programmed.
 * The bitflips_threshold specify the maximum number of bitflips before
 * considering the region as not erased.
 *
 * Note:
 * 1/ ECC algorithms are working on pre-defined block sizes which are usually
 *    different from the NAND page size. When fixing bitflips, ECC engines will
 *    report the number of errors per chunk, and the NAND core infrastructure
 *    expect you to return the maximum number of bitflips for the whole page.
 *    This is why you should always use this function on a single chunk and
 *    not on the whole page. After checking each chunk you should update your
 *    max_bitflips value accordingly.
 * 2/ When checking for bitflips in erased pages you should not only check
 *    the payload data but also their associated ECC data, because a user might
 *    have programmed almost all bits to 1 but a few. In this case, we
 *    shouldn't consider the chunk as erased, and checking ECC bytes prevent
 *    this case.
 * 3/ The extraoob argument is optional, and should be used if some of your OOB
 *    data are protected by the ECC engine.
 *    It could also be used if you support subpages and want to attach some
 *    extra OOB data to an ECC chunk.
 *
 * Returns a positive number of bitflips less than or equal to
 * bitflips_threshold, or -ERROR_CODE for bitflips in excess of the
 * threshold. In case of success, the passed buffers are filled with 0xff.
 */
int nand_check_erased_ecc_chunk(void *data, int datalen,
				void *ecc, int ecclen,
				void *extraoob, int extraooblen,
				int bitflips_threshold)
{
	int data_bitflips = 0, ecc_bitflips = 0, extraoob_bitflips = 0;

	data_bitflips = nand_check_erased_buf(data, datalen,
					      bitflips_threshold);
	if (data_bitflips < 0)
		return data_bitflips;

	bitflips_threshold -= data_bitflips;

	ecc_bitflips = nand_check_erased_buf(ecc, ecclen, bitflips_threshold);
	if (ecc_bitflips < 0)
		return ecc_bitflips;

	bitflips_threshold -= ecc_bitflips;

	extraoob_bitflips = nand_check_erased_buf(extraoob, extraooblen,
						  bitflips_threshold);
	if (extraoob_bitflips < 0)
		return extraoob_bitflips;

	if (data_bitflips)
		memset(data, 0xff, datalen);

	if (ecc_bitflips)
		memset(ecc, 0xff, ecclen);

	if (extraoob_bitflips)
		memset(extraoob, 0xff, extraooblen);

	return data_bitflips + ecc_bitflips + extraoob_bitflips;
}
EXPORT_SYMBOL(nand_check_erased_ecc_chunk);

/**
 * nanddev_isbad() - Check if a block is bad
 * @nand: NAND device
 * @pos: position pointing to the block we want to check
 *
 * Return: true if the block is bad, false otherwise.
 */
bool nanddev_isbad(struct nand_device *nand, const struct nand_pos *pos)
{
	if (mtd_check_expert_analysis_mode())
		return false;

	if (nanddev_bbt_is_initialized(nand)) {
		unsigned int entry;
		int status;

		entry = nanddev_bbt_pos_to_entry(nand, pos);
		status = nanddev_bbt_get_block_status(nand, entry);
		/* Lazy block status retrieval */
		if (status == NAND_BBT_BLOCK_STATUS_UNKNOWN) {
			if (nand->ops->isbad(nand, pos))
				status = NAND_BBT_BLOCK_FACTORY_BAD;
			else
				status = NAND_BBT_BLOCK_GOOD;

			nanddev_bbt_set_block_status(nand, entry, status);
		}

		if (status == NAND_BBT_BLOCK_WORN ||
		    status == NAND_BBT_BLOCK_FACTORY_BAD)
			return true;

		return false;
	}

	return nand->ops->isbad(nand, pos);
}
EXPORT_SYMBOL_GPL(nanddev_isbad);

/**
 * nanddev_markbad() - Mark a block as bad
 * @nand: NAND device
 * @pos: position of the block to mark bad
 *
 * Mark a block bad. This function is updating the BBT if available and
 * calls the low-level markbad hook (nand->ops->markbad()).
 *
 * Return: 0 in case of success, a negative error code otherwise.
 */
int nanddev_markbad(struct nand_device *nand, const struct nand_pos *pos)
{
	struct mtd_info *mtd = nanddev_to_mtd(nand);
	unsigned int entry;
	int ret = 0;

	if (nanddev_isbad(nand, pos))
		return 0;

	ret = nand->ops->markbad(nand, pos);
	if (ret)
		pr_warn("failed to write BBM to block @%llx (err = %d)\n",
			nanddev_pos_to_offs(nand, pos), ret);

	if (!nanddev_bbt_is_initialized(nand))
		goto out;

	entry = nanddev_bbt_pos_to_entry(nand, pos);
	ret = nanddev_bbt_set_block_status(nand, entry, NAND_BBT_BLOCK_WORN);
	if (ret)
		goto out;

	ret = nanddev_bbt_update(nand);

out:
	if (!ret)
		mtd->ecc_stats.badblocks++;

	return ret;
}
EXPORT_SYMBOL_GPL(nanddev_markbad);

/**
 * nanddev_isreserved() - Check whether an eraseblock is reserved or not
 * @nand: NAND device
 * @pos: NAND position to test
 *
 * Checks whether the eraseblock pointed by @pos is reserved or not.
 *
 * Return: true if the eraseblock is reserved, false otherwise.
 */
bool nanddev_isreserved(struct nand_device *nand, const struct nand_pos *pos)
{
	unsigned int entry;
	int status;

	if (!nanddev_bbt_is_initialized(nand))
		return false;

	/* Return info from the table */
	entry = nanddev_bbt_pos_to_entry(nand, pos);
	status = nanddev_bbt_get_block_status(nand, entry);
	return status == NAND_BBT_BLOCK_RESERVED;
}
EXPORT_SYMBOL_GPL(nanddev_isreserved);

/**
 * nanddev_erase() - Erase a NAND portion
 * @nand: NAND device
 * @pos: position of the block to erase
 *
 * Erases the block if it's not bad.
 *
 * Return: 0 in case of success, a negative error code otherwise.
 */
static int nanddev_erase(struct nand_device *nand, const struct nand_pos *pos)
{
	if (nanddev_isbad(nand, pos) || nanddev_isreserved(nand, pos)) {
		pr_warn("attempt to erase a bad/reserved block @%llx\n",
			nanddev_pos_to_offs(nand, pos));
		return -EIO;
	}

	return nand->ops->erase(nand, pos);
}

/**
 * nanddev_mtd_erase() - Generic mtd->_erase() implementation for NAND devices
 * @mtd: MTD device
 * @einfo: erase request
 *
 * This is a simple mtd->_erase() implementation iterating over all blocks
 * concerned by @einfo and calling nand->ops->erase() on each of them.
 *
 * Note that mtd->_erase should not be directly assigned to this helper,
 * because there's no locking here. NAND specialized layers should instead
 * implement there own wrapper around nanddev_mtd_erase() taking the
 * appropriate lock before calling nanddev_mtd_erase().
 *
 * Return: 0 in case of success, a negative error code otherwise.
 */
int nanddev_mtd_erase(struct mtd_info *mtd, struct erase_info *einfo)
{
	struct nand_device *nand = mtd_to_nanddev(mtd);
	struct nand_pos pos, last;
	int ret;

	nanddev_offs_to_pos