drivers/mtd/spi-nor/otp.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * OTP support for SPI NOR flashes
  *
  * Copyright (C) 2021 Michael Walle <michael@walle.cc>
  */

 #include <linux/log2.h>
 #include <linux/mtd/mtd.h>
 #include <linux/mtd/spi-nor.h>

 #include "core.h"

 #define spi_nor_otp_region_len(nor) ((nor)->params->otp.org->len)
 #define spi_nor_otp_n_regions(nor) ((nor)->params->otp.org->n_regions)

 /**
  * spi_nor_otp_read_secr() - read security register
  * @nor:	pointer to 'struct spi_nor'
  * @addr:       offset to read from
  * @len:        number of bytes to read
  * @buf:        pointer to dst buffer
  *
  * Read a security register by using the SPINOR_OP_RSECR commands.
  *
  * In Winbond/GigaDevice datasheets the term "security register" stands for
  * an one-time-programmable memory area, consisting of multiple bytes (usually
  * 256). Thus one "security register" maps to one OTP region.
  *
  * This method is used on GigaDevice and Winbond flashes.
  *
  * Please note, the read must not span multiple registers.
  *
  * Return: number of bytes read successfully, -errno otherwise
  */
 int spi_nor_otp_read_secr(struct spi_nor *nor, loff_t addr, size_t len, u8 *buf)
 {
 	u8 addr_width, read_opcode, read_dummy;
 	struct spi_mem_dirmap_desc *rdesc;
 	enum spi_nor_protocol read_proto;
 	int ret;

 	read_opcode = nor->read_opcode;
 	addr_width = nor->addr_width;
 	read_dummy = nor->read_dummy;
 	read_proto = nor->read_proto;
 	rdesc = nor->dirmap.rdesc;

 	nor->read_opcode = SPINOR_OP_RSECR;
 	nor->read_dummy = 8;
 	nor->read_proto = SNOR_PROTO_1_1_1;
 	nor->dirmap.rdesc = NULL;

 	ret = spi_nor_read_data(nor, addr, len, buf);

 	nor->read_opcode = read_opcode;
 	nor->addr_width = addr_width;
 	nor->read_dummy = read_dummy;
 	nor->read_proto = read_proto;
 	nor->dirmap.rdesc = rdesc;

 	return ret;
 }

 /**
  * spi_nor_otp_write_secr() - write security register
  * @nor:        pointer to 'struct spi_nor'
  * @addr:       offset to write to
  * @len:        number of bytes to write
  * @buf:        pointer to src buffer
  *
  * Write a security register by using the SPINOR_OP_PSECR commands.
  *
  * For more information on the term "security register", see the documentation
  * of spi_nor_otp_read_secr().
  *
  * This method is used on GigaDevice and Winbond flashes.
  *
  * Please note, the write must not span multiple registers.
  *
  * Return: number of bytes written successfully, -errno otherwise
  */
 int spi_nor_otp_write_secr(struct spi_nor *nor, loff_t addr, size_t len,
 			   const u8 *buf)
 {
 	enum spi_nor_protocol write_proto;
 	struct spi_mem_dirmap_desc *wdesc;
 	u8 addr_width, program_opcode;
 	int ret, written;

 	program_opcode = nor->program_opcode;
 	addr_width = nor->addr_width;
 	write_proto = nor->write_proto;
 	wdesc = nor->dirmap.wdesc;

 	nor->program_opcode = SPINOR_OP_PSECR;
 	nor->write_proto = SNOR_PROTO_1_1_1;
 	nor->dirmap.wdesc = NULL;

 	/*
 	 * We only support a write to one single page. For now all winbond
 	 * flashes only have one page per security register.
 	 */
 	ret = spi_nor_write_enable(nor);
 	if (ret)
 		goto out;

 	written = spi_nor_write_data(nor, addr, len, buf);
 	if (written < 0)
 		goto out;

 	ret = spi_nor_wait_till_ready(nor);

 out:
 	nor->program_opcode = program_opcode;
 	nor->addr_width = addr_width;
 	nor->write_proto = write_proto;
 	nor->dirmap.wdesc = wdesc;

 	return ret ?: written;
 }

 /**
  * spi_nor_otp_erase_secr() - erase a security register
  * @nor:        pointer to 'struct spi_nor'
  * @addr:       offset of the security register to be erased
  *
  * Erase a security register by using the SPINOR_OP_ESECR command.
  *
  * For more information on the term "security register", see the documentation
  * of spi_nor_otp_read_secr().
  *
  * This method is used on GigaDevice and Winbond flashes.
  *
  * Return: 0 on success, -errno otherwise
  */
 int spi_nor_otp_erase_secr(struct spi_nor *nor, loff_t addr)
 {
 	u8 erase_opcode = nor->erase_opcode;
 	int ret;

 	ret = spi_nor_write_enable(nor);
 	if (ret)
 		return ret;

 	nor->erase_opcode = SPINOR_OP_ESECR;
 	ret = spi_nor_erase_sector(nor, addr);
 	nor->erase_opcode = erase_opcode;
 	if (ret)
 		return ret;

 	return spi_nor_wait_till_ready(nor);
 }

 static int spi_nor_otp_lock_bit_cr(unsigned int region)
 {
 	static const int lock_bits[] = { SR2_LB1, SR2_LB2, SR2_LB3 };

 	if (region >= ARRAY_SIZE(lock_bits))
 		return -EINVAL;

 	return lock_bits[region];
 }

 /**
  * spi_nor_otp_lock_sr2() - lock the OTP region
  * @nor:        pointer to 'struct spi_nor'
  * @region:     OTP region
  *
  * Lock the OTP region by writing the status register-2. This method is used on
  * GigaDevice and Winbond flashes.
  *
  * Return: 0 on success, -errno otherwise.
  */
 int spi_nor_otp_lock_sr2(struct spi_nor *nor, unsigned int region)
 {
 	u8 *cr = nor->bouncebuf;
 	int ret, lock_bit;

 	lock_bit = spi_nor_otp_lock_bit_cr(region);
 	if (lock_bit < 0)
 		return lock_bit;

 	ret = spi_nor_read_cr(nor, cr);
 	if (ret)
 		return ret;

 	/* no need to write the register if region is already locked */
 	if (cr[0] & lock_bit)
 		return 0;

 	cr[0] |= lock_bit;

 	return spi_nor_write_16bit_cr_and_check(nor, cr[0]);
 }

 /**
  * spi_nor_otp_is_locked_sr2() - get the OTP region lock status
  * @nor:        pointer to 'struct spi_nor'
  * @region:     OTP region
  *
  * Retrieve the OTP region lock bit by reading the status register-2. This
  * method is used on GigaDevice and Winbond flashes.
  *
  * Return: 0 on success, -errno otherwise.
  */
 int spi_nor_otp_is_locked_sr2(struct spi_nor *nor, unsigned int region)
 {
 	u8 *cr = nor->bouncebuf;
 	int ret, lock_bit;

 	lock_bit = spi_nor_otp_lock_bit_cr(region);
 	if (lock_bit < 0)
 		return lock_bit;

 	ret = spi_nor_read_cr(nor, cr);
 	if (ret)
 		return ret;

 	return cr[0] & lock_bit;
 }

 static loff_t spi_nor_otp_region_start(const struct spi_nor *nor, unsigned int region)
 {
 	const struct spi_nor_otp_organization *org = nor->params->otp.org;

 	return org->base + region * org->offset;
 }

 static size_t spi_nor_otp_size(struct spi_nor *nor)
 {
 	return spi_nor_otp_n_regions(nor) * spi_nor_otp_region_len(nor);
 }

 /* Translate the file offsets from and to OTP regions. */
 static loff_t spi_nor_otp_region_to_offset(struct spi_nor *nor, unsigned int region)
 {
 	return region * spi_nor_otp_region_len(nor);
 }

 static unsigned int spi_nor_otp_offset_to_region(struct spi_nor *nor, loff_t ofs)
 {
 	return div64_u64(ofs, spi_nor_otp_region_len(nor));
 }

 static int spi_nor_mtd_otp_info(struct mtd_info *mtd, size_t len,
 				size_t *retlen, struct otp_info *buf)
 {
 	struct spi_nor *nor = mtd_to_spi_nor(mtd);
 	const struct spi_nor_otp_ops *ops = nor->params->otp.ops;
 	unsigned int n_regions = spi_nor_otp_n_regions(nor);
 	unsigned int i;
 	int ret, locked;

 	if (len < n_regions * sizeof(*buf))
 		return -ENOSPC;

 	ret = spi_nor_lock_and_prep(nor);
 	if (ret)
 		return ret;

 	for (i = 0; i < n_regions; i++) {
 		buf->start = spi_nor_otp_region_to_offset(nor, i);
 		buf->length = spi_nor_otp_region_len(nor);

 		locked = ops->is_locked(nor, i);
 		if (locked < 0) {
 			ret = locked;
 			goto out;
 		}

 		buf->locked = !!locked;
 		buf++;
 	}

 	*retlen = n_regions * sizeof(*buf);

 out:
 	spi_nor_unlock_and_unprep(nor);

 	return ret;
 }

 static int spi_nor_mtd_otp_range_is_locked(struct spi_nor *nor, loff_t ofs,
 					   size_t len)
 {
 	const struct spi_nor_otp_ops *ops = nor->params->otp.ops;
 	unsigned int region;
 	int locked;

 	/*
 	 * If any of the affected OTP regions are locked the entire range is
 	 * considered locked.
 	 */
 	for (region = spi_nor_otp_offset_to_region(nor, ofs);
 	     region <= spi_nor_otp_offset_to_region(nor, ofs + len - 1);
 	     region++) {
 		locked = ops->is_locked(nor, region);
 		/* take the branch it is locked or in case of an error */
 		if (locked)
 			return locked;
 	}

 	return 0;
 }

 static int spi_nor_mtd_otp_read_write(struct mtd_info *mtd, loff_t ofs,
 				      size_t total_len, size_t *retlen,
 				      const u8 *buf, bool is_write)
 {
 	struct spi_nor *nor = mtd_to_spi_nor(mtd);
 	const struct spi_nor_otp_ops *ops = nor->params->otp.ops;
 	const size_t rlen = spi_nor_otp_region_len(nor);
 	loff_t rstart, rofs;
 	unsigned int region;
 	size_t len;
 	int ret;

 	if (ofs < 0 || ofs >= spi_nor_otp_size(nor))
 		return 0;

 	/* don't access beyond the end */
 	total_len = min_t(size_t, total_len, spi_nor_otp_size(nor) - ofs);

 	if (!total_len)
 		return 0;

 	ret = spi_nor_lock_and_prep(nor);
 	if (ret)
 		return ret;

 	if (is_write) {
 		ret = spi_nor_mtd_otp_range_is_locked(nor, ofs, total_len);
 		if (ret < 0) {
 			goto out;
 		} else if (ret) {
 			ret = -EROFS;
 			goto out;
 		}
 	}

 	while (total_len) {
 		/*
 		 * The OTP regions are mapped into a contiguous area starting
 		 * at 0 as expected by the MTD layer. This will map the MTD
 		 * file offsets to the address of an OTP region as used in the
 		 * actual SPI commands.
 		 */
 		region = spi_nor_otp_offset_to_region(nor, ofs);
 		rstart = spi_nor_otp_region_start(nor, region);

 		/*
 		 * The size of a OTP region is expected to be a power of two,
 		 * thus we can just mask the lower bits and get the offset into
 		 * a region.
 		 */
 		rofs = ofs & (rlen - 1);

 		/* don't access beyond one OTP region */
 		len = min_t(size_t, total_len, rlen - rofs);

 		if (is_write)
 			ret = ops->write(nor, rstart + rofs, len, buf);
 		else
 			ret = ops->read(nor, rstart + rofs, len, (u8 *)buf);
 		if (ret == 0)
 			ret = -EIO;
 		if (ret < 0)
 			goto out;

 		*retlen += ret;
 		ofs += ret;
 		buf += ret;
 		total_len -= ret;
 	}
 	ret = 0;

 out:
 	spi_nor_unlock_and_unprep(nor);
 	return ret;
 }

 static int spi_nor_mtd_otp_read(struct mtd_info *mtd, loff_t from, size_t len,
 				size_t *retlen, u8 *buf)
 {
 	return spi_nor_mtd_otp_read_write(mtd, from, len, retlen, buf, false);
 }

 static int spi_nor_mtd_otp_write(struct mtd_info *mtd, loff_t to, size_t len,
 				 size_t *retlen, const u8 *buf)
 {
 	return spi_nor_mtd_otp_read_write(mtd, to, len, retlen, buf, true);
 }

 static int spi_nor_mtd_otp_erase(struct mtd_info *mtd, loff_t from, size_t len)
 {
 	struct spi_nor *nor = mtd_to_spi_nor(mtd);
 	const struct spi_nor_otp_ops *ops = nor->params->otp.ops;
 	const size_t rlen = spi_nor_otp_region_len(nor);
 	unsigned int region;
 	loff_t rstart;
 	int ret;

 	/* OTP erase is optional */
 	if (!ops->erase)
 		return -EOPNOTSUPP;

 	if (!len)
 		return 0;

 	if (from < 0 || (from + len) > spi_nor_otp_size(nor))
 		return -EINVAL;

 	/* the user has to explicitly ask for whole regions */
 	if (!IS_ALIGNED(len, rlen) || !IS_ALIGNED(from, rlen))
 		return -EINVAL;

 	ret = spi_nor_lock_and_prep(nor);
 	if (ret)
 		return ret;

 	ret = spi_nor_mtd_otp_range_is_locked(nor, from, len);
 	if (ret < 0) {
 		goto out;
 	} else if (ret) {
 		ret = -EROFS;
 		goto out;
 	}

 	while (len) {
 		region = spi_nor_otp_offset_to_region(nor, from);
 		rstart = spi_nor_otp_region_start(nor, region);

 		ret = ops->erase(nor, rstart);
 		if (ret)
 			goto out;

 		len -= rlen;
 		from += rlen;
 	}

 out:
 	spi_nor_unlock_and_unprep(nor);

 	return ret;
 }

 static int spi_nor_mtd_otp_lock(struct mtd_info *mtd, loff_t from, size_t len)
 {
 	struct spi_nor *nor = mtd_to_spi_nor(mtd);
 	const struct spi_nor_otp_ops *ops = nor->params->otp.ops;
 	const size_t rlen = spi_nor_otp_region_len(nor);
 	unsigned int region;
 	int ret;

 	if (from < 0 || (from + len) > spi_nor_otp_size(nor))
 		return -EINVAL;

 	/* the user has to explicitly ask for whole regions */
 	if (!IS_ALIGNED(len, rlen) || !IS_ALIGNED(from, rlen))
 		return -EINVAL;

 	ret = spi_nor_lock_and_prep(nor);
 	if (ret)
 		return ret;

 	while (len) {
 		region = spi_nor_otp_offset_to_region(nor, from);
 		ret = ops->lock(nor, region);
 		if (ret)
 			goto out;

 		len -= rlen;
 		from += rlen;
 	}

 out:
 	spi_nor_unlock_and_unprep(nor);

 	return ret;
 }

 void spi_nor_set_mtd_otp_ops(struct spi_nor *nor)
 {
 	struct mtd_info *mtd = &nor->mtd;

 	if (!nor->params->otp.ops)
 		return;

 	if (WARN_ON(!is_power_of_2(spi_nor_otp_region_len(nor))))
 		return;

 	/*
 	 * We only support user_prot callbacks (yet).
 	 *
 	 * Some SPI NOR flashes like Macronix ones can be ordered in two
 	 * different variants. One with a factory locked OTP area and one where
 	 * it is left to the user to write to it. The factory locked OTP is
 	 * usually preprogrammed with an "electrical serial number". We don't
 	 * support these for now.
 	 */
 	mtd->_get_user_prot_info = spi_nor_mtd_otp_info;
 	mtd->_read_user_prot_reg = spi_nor_mtd_otp_read;
 	mtd->_write_user_prot_reg = spi_nor_mtd_otp_write;
 	mtd->_lock_user_prot_reg = spi_nor_mtd_otp_lock;
 	mtd->_erase_user_prot_reg = spi_nor_mtd_otp_erase;
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* OTP support for SPI NOR flashes
	*
	* Copyright (C) 2021 Michael Walle <michael@walle.cc>
	*/

	#include <linux/log2.h>
	#include <linux/mtd/mtd.h>
	#include <linux/mtd/spi-nor.h>

	#include "core.h"

	#define spi_nor_otp_region_len(nor) ((nor)->params->otp.org->len)
	#define spi_nor_otp_n_regions(nor) ((nor)->params->otp.org->n_regions)

	/**
	* spi_nor_otp_read_secr() - read security register
	* @nor: pointer to 'struct spi_nor'
	* @addr: offset to read from
	* @len: number of bytes to read
	* @buf: pointer to dst buffer
	*
	* Read a security register by using the SPINOR_OP_RSECR commands.
	*
	* In Winbond/GigaDevice datasheets the term "security register" stands for
	* an one-time-programmable memory area, consisting of multiple bytes (usually
	* 256). Thus one "security register" maps to one OTP region.
	*
	* This method is used on GigaDevice and Winbond flashes.
	*
	* Please note, the read must not span multiple registers.
	*
	* Return: number of bytes read successfully, -errno otherwise
	*/
	int spi_nor_otp_read_secr(struct spi_nor nor, loff_t addr, size_t len, u8 buf)
	{
	u8 addr_width, read_opcode, read_dummy;
	struct spi_mem_dirmap_desc *rdesc;
	enum spi_nor_protocol read_proto;
	int ret;

	read_opcode = nor->read_opcode;
	addr_width = nor->addr_width;
	read_dummy = nor->read_dummy;
	read_proto = nor->read_proto;
	rdesc = nor->dirmap.rdesc;

	nor->read_opcode = SPINOR_OP_RSECR;
	nor->read_dummy = 8;
	nor->read_proto = SNOR_PROTO_1_1_1;
	nor->dirmap.rdesc = NULL;

	ret = spi_nor_read_data(nor, addr, len, buf);

	nor->read_opcode = read_opcode;
	nor->addr_width = addr_width;
	nor->read_dummy = read_dummy;
	nor->read_proto = read_proto;
	nor->dirmap.rdesc = rdesc;

	return ret;
	}

	/**
	* spi_nor_otp_write_secr() - write security register
	* @nor: pointer to 'struct spi_nor'
	* @addr: offset to write to
	* @len: number of bytes to write
	* @buf: pointer to src buffer
	*
	* Write a security register by using the SPINOR_OP_PSECR commands.
	*
	* For more information on the term "security register", see the documentation
	* of spi_nor_otp_read_secr().
	*
	* This method is used on GigaDevice and Winbond flashes.
	*
	* Please note, the write must not span multiple registers.
	*
	* Return: number of bytes written successfully, -errno otherwise
	*/
	int spi_nor_otp_write_secr(struct spi_nor *nor, loff_t addr, size_t len,
	const u8 *buf)
	{
	enum spi_nor_protocol write_proto;
	struct spi_mem_dirmap_desc *wdesc;
	u8 addr_width, program_opcode;
	int ret, written;

	program_opcode = nor->program_opcode;
	addr_width = nor->addr_width;
	write_proto = nor->write_proto;
	wdesc = nor->dirmap.wdesc;

	nor->program_opcode = SPINOR_OP_PSECR;
	nor->write_proto = SNOR_PROTO_1_1_1;
	nor->dirmap.wdesc = NULL;

	/*
	* We only support a write to one single page. For now all winbond
	* flashes only have one page per security register.
	*/
	ret = spi_nor_write_enable(nor);
	if (ret)
	goto out;

	written = spi_nor_write_data(nor, addr, len, buf);
	if (written < 0)
	goto out;

	ret = spi_nor_wait_till_ready(nor);

	out:
	nor->program_opcode = program_opcode;
	nor->addr_width = addr_width;
	nor->write_proto = write_proto;
	nor->dirmap.wdesc = wdesc;

	return ret ?: written;
	}

	/**
	* spi_nor_otp_erase_secr() - erase a security register
	* @nor: pointer to 'struct spi_nor'
	* @addr: offset of the security register to be erased
	*
	* Erase a security register by using the SPINOR_OP_ESECR command.
	*
	* For more information on the term "security register", see the documentation
	* of spi_nor_otp_read_secr().
	*
	* This method is used on GigaDevice and Winbond flashes.
	*
	* Return: 0 on success, -errno otherwise
	*/
	int spi_nor_otp_erase_secr(struct spi_nor *nor, loff_t addr)
	{
	u8 erase_opcode = nor->erase_opcode;
	int ret;

	ret = spi_nor_write_enable(nor);
	if (ret)
	return ret;

	nor->erase_opcode = SPINOR_OP_ESECR;
	ret = spi_nor_erase_sector(nor, addr);
	nor->erase_opcode = erase_opcode;
	if (ret)
	return ret;

	return spi_nor_wait_till_ready(nor);
	}

	static int spi_nor_otp_lock_bit_cr(unsigned int region)
	{
	static const int lock_bits[] = { SR2_LB1, SR2_LB2, SR2_LB3 };

	if (region >= ARRAY_SIZE(lock_bits))
	return -EINVAL;

	return lock_bits[region];
	}

	/**
	* spi_nor_otp_lock_sr2() - lock the OTP region
	* @nor: pointer to 'struct spi_nor'
	* @region: OTP region
	*
	* Lock the OTP region by writing the status register-2. This method is used on
	* GigaDevice and Winbond flashes.
	*
	* Return: 0 on success, -errno otherwise.
	*/
	int spi_nor_otp_lock_sr2(struct spi_nor *nor, unsigned int region)
	{
	u8 *cr = nor->bouncebuf;
	int ret, lock_bit;

	lock_bit = spi_nor_otp_lock_bit_cr(region);
	if (lock_bit < 0)
	return lock_bit;

	ret = spi_nor_read_cr(nor, cr);
	if (ret)
	return ret;

	/* no need to write the register if region is already locked */
	if (cr[0] & lock_bit)
	return 0;

	cr[0] \|= lock_bit;

	return spi_nor_write_16bit_cr_and_check(nor, cr[0]);
	}

	/**
	* spi_nor_otp_is_locked_sr2() - get the OTP region lock status
	* @nor: pointer to 'struct spi_nor'
	* @region: OTP region
	*
	* Retrieve the OTP region lock bit by reading the status register-2. This
	* method is used on GigaDevice and Winbond flashes.
	*
	* Return: 0 on success, -errno otherwise.
	*/
	int spi_nor_otp_is_locked_sr2(struct spi_nor *nor, unsigned int region)
	{
	u8 *cr = nor->bouncebuf;
	int ret, lock_bit;

	lock_bit = spi_nor_otp_lock_bit_cr(region);
	if (lock_bit < 0)
	return lock_bit;

	ret = spi_nor_read_cr(nor, cr);
	if (ret)
	return ret;

	return cr[0] & lock_bit;
	}

	static loff_t spi_nor_otp_region_start(const struct spi_nor *nor, unsigned int region)
	{
	const struct spi_nor_otp_organization *org = nor->params->otp.org;

	return org->base + region * org->offset;
	}

	static size_t spi_nor_otp_size(struct spi_nor *nor)
	{
	return spi_nor_otp_n_regions(nor) * spi_nor_otp_region_len(nor);
	}

	/* Translate the file offsets from and to OTP regions. */
	static loff_t spi_nor_otp_region_to_offset(struct spi_nor *nor, unsigned int region)
	{
	return region * spi_nor_otp_region_len(nor);
	}

	static unsigned int spi_nor_otp_offset_to_region(struct spi_nor *nor, loff_t ofs)
	{
	return div64_u64(ofs, spi_nor_otp_region_len(nor));
	}

	static int spi_nor_mtd_otp_info(struct mtd_info *mtd, size_t len,
	size_t retlen, struct otp_info buf)
	{
	struct spi_nor *nor = mtd_to_spi_nor(mtd);
	const struct spi_nor_otp_ops *ops = nor->params->otp.ops;
	unsigned int n_regions = spi_nor_otp_n_regions(nor);
	unsigned int i;
	int ret, locked;

	if (len < n_regions * sizeof(*buf))
	return -ENOSPC;

	ret = spi_nor_lock_and_prep(nor);
	if (ret)
	return ret;

	for (i = 0; i < n_regions; i++) {
	buf->start = spi_nor_otp_region_to_offset(nor, i);
	buf->length = spi_nor_otp_region_len(nor);

	locked = ops->is_locked(nor, i);
	if (locked < 0) {
	ret = locked;
	goto out;
	}

	buf->locked = !!locked;
	buf++;
	}

	retlen = n_regions sizeof(*buf);

	out:
	spi_nor_unlock_and_unprep(nor);

	return ret;
	}

	static int spi_nor_mtd_otp_range_is_locked(struct spi_nor *nor, loff_t ofs,
	size_t len)
	{
	const struct spi_nor_otp_ops *ops = nor->params->otp.ops;
	unsigned int region;
	int locked;

	/*
	* If any of the affected OTP regions are locked the entire range is
	* considered locked.
	*/
	for (region = spi_nor_otp_offset_to_region(nor, ofs);
	region <= spi_nor_otp_offset_to_region(nor, ofs + len - 1);
	region++) {
	locked = ops->is_locked(nor, region);
	/* take the branch it is locked or in case of an error */
	if (locked)
	return locked;
	}

	return 0;
	}

	static int spi_nor_mtd_otp_read_write(struct mtd_info *mtd, loff_t ofs,
	size_t total_len, size_t *retlen,
	const u8 *buf, bool is_write)
	{
	struct spi_nor *nor = mtd_to_spi_nor(mtd);
	const struct spi_nor_otp_ops *ops = nor->params->otp.ops;
	const size_t rlen = spi_nor_otp_region_len(nor);
	loff_t rstart, rofs;
	unsigned int region;
	size_t len;
	int ret;

	if (ofs < 0 \|\| ofs >= spi_nor_otp_size(nor))
	return 0;

	/* don't access beyond the end */
	total_len = min_t(size_t, total_len, spi_nor_otp_size(nor) - ofs);

	if (!total_len)
	return 0;

	ret = spi_nor_lock_and_prep(nor);
	if (ret)
	return ret;

	if (is_write) {
	ret = spi_nor_mtd_otp_range_is_locked(nor, ofs, total_len);
	if (ret < 0) {
	goto out;
	} else if (ret) {
	ret = -EROFS;
	goto out;
	}
	}

	while (total_len) {
	/*
	* The OTP regions are mapped into a contiguous area starting
	* at 0 as expected by the MTD layer. This will map the MTD
	* file offsets to the address of an OTP region as used in the
	* actual SPI commands.
	*/
	region = spi_nor_otp_offset_to_region(nor, ofs);
	rstart = spi_nor_otp_region_start(nor, region);

	/*
	* The size of a OTP region is expected to be a power of two,
	* thus we can just mask the lower bits and get the offset into
	* a region.
	*/
	rofs = ofs & (rlen - 1);

	/* don't access beyond one OTP region */
	len = min_t(size_t, total_len, rlen - rofs);

	if (is_write)
	ret = ops->write(nor, rstart + rofs, len, buf);
	else
	ret = ops->read(nor, rstart + rofs, len, (u8 *)buf);
	if (ret == 0)
	ret = -EIO;
	if (ret < 0)
	goto out;

	*retlen += ret;
	ofs += ret;
	buf += ret;
	total_len -= ret;
	}
	ret = 0;

	out:
	spi_nor_unlock_and_unprep(nor);
	return ret;
	}

	static int spi_nor_mtd_otp_read(struct mtd_info *mtd, loff_t from, size_t len,
	size_t retlen, u8 buf)
	{
	return spi_nor_mtd_otp_read_write(mtd, from, len, retlen, buf, false);
	}

	static int spi_nor_mtd_otp_write(struct mtd_info *mtd, loff_t to, size_t len,
	size_t retlen, const u8 buf)
	{
	return spi_nor_mtd_otp_read_write(mtd, to, len, retlen, buf, true);
	}

	static int spi_nor_mtd_otp_erase(struct mtd_info *mtd, loff_t from, size_t len)
	{
	struct spi_nor *nor = mtd_to_spi_nor(mtd);
	const struct spi_nor_otp_ops *ops = nor->params->otp.ops;
	const size_t rlen = spi_nor_otp_region_len(nor);
	unsigned int region;
	loff_t rstart;
	int ret;

	/* OTP erase is optional */
	if (!ops->erase)
	return -EOPNOTSUPP;

	if (!len)
	return 0;

	if (from < 0 \|\| (from + len) > spi_nor_otp_size(nor))
	return -EINVAL;

	/* the user has to explicitly ask for whole regions */
	if (!IS_ALIGNED(len, rlen) \|\| !IS_ALIGNED(from, rlen))
	return -EINVAL;

	ret = spi_nor_lock_and_prep(nor);
	if (ret)
	return ret;

	ret = spi_nor_mtd_otp_range_is_locked(nor, from, len);
	if (ret < 0) {
	goto out;
	} else if (ret) {
	ret = -EROFS;
	goto out;
	}

	while (len) {
	region = spi_nor_otp_offset_to_region(nor, from);
	rstart = spi_nor_otp_region_start(nor, region);

	ret = ops->erase(nor, rstart);
	if (ret)
	goto out;

	len -= rlen;
	from += rlen;
	}

	out:
	spi_nor_unlock_and_unprep(nor);

	return ret;
	}

	static int spi_nor_mtd_otp_lock(struct mtd_info *mtd, loff_t from, size_t len)
	{
	struct spi_nor *nor = mtd_to_spi_nor(mtd);
	const struct spi_nor_otp_ops *ops = nor->params->otp.ops;
	const size_t rlen = spi_nor_otp_region_len(nor);
	unsigned int region;
	int ret;

	if (from < 0 \|\| (from + len) > spi_nor_otp_size(nor))
	return -EINVAL;

	/* the user has to explicitly ask for whole regions */
	if (!IS_ALIGNED(len, rlen) \|\| !IS_ALIGNED(from, rlen))
	return -EINVAL;

	ret = spi_nor_lock_and_prep(nor);
	if (ret)
	return ret;

	while (len) {
	region = spi_nor_otp_offset_to_region(nor, from);
	ret = ops->lock(nor, region);
	if (ret)
	goto out;

	len -= rlen;
	from += rlen;
	}

	out:
	spi_nor_unlock_and_unprep(nor);

	return ret;
	}

	void spi_nor_set_mtd_otp_ops(struct spi_nor *nor)
	{
	struct mtd_info *mtd = &nor->mtd;

	if (!nor->params->otp.ops)
	return;

	if (WARN_ON(!is_power_of_2(spi_nor_otp_region_len(nor))))
	return;

	/*
	* We only support user_prot callbacks (yet).
	*
	* Some SPI NOR flashes like Macronix ones can be ordered in two
	* different variants. One with a factory locked OTP area and one where
	* it is left to the user to write to it. The factory locked OTP is
	* usually preprogrammed with an "electrical serial number". We don't
	* support these for now.
	*/
	mtd->_get_user_prot_info = spi_nor_mtd_otp_info;
	mtd->_read_user_prot_reg = spi_nor_mtd_otp_read;
	mtd->_write_user_prot_reg = spi_nor_mtd_otp_write;
	mtd->_lock_user_prot_reg = spi_nor_mtd_otp_lock;
	mtd->_erase_user_prot_reg = spi_nor_mtd_otp_erase;
	}