mtd: spinand: add OTP support

The MTD subsystem already supports accessing two OTP areas: user and
factory. User areas can be written by the user.

This patch provides the SPINAND_FACT_OTP_INFO and SPINAND_USER_OTP_INFO
macros to add parameters to spinand_info.
To implement OTP operations, the client (flash driver) is provided with
callbacks for user area:
    .read(), .write(), .info(), .lock(), .erase();
and for factory area:
    .read(), .info();

Signed-off-by: Martin Kurbanov <mmkurbanov@salutedevices.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

drivers/mtd/nand/spi/Makefile

@@ -1,4 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
-spinand-objs := core.o alliancememory.o ato.o esmt.o foresee.o gigadevice.o macronix.o
+spinand-objs := core.o otp.o
+spinand-objs += alliancememory.o ato.o esmt.o foresee.o gigadevice.o macronix.o
 spinand-objs += micron.o paragon.o skyhigh.o toshiba.o winbond.o xtx.o
 obj-$(CONFIG_MTD_SPI_NAND) += spinand.o

drivers/mtd/nand/spi/core.c

@@ -1308,6 +1308,8 @@ int spinand_match_and_init(struct spinand_device *spinand,
 		spinand->id.len = 1 + table[i].devid.len;
 		spinand->select_target = table[i].select_target;
 		spinand->set_cont_read = table[i].set_cont_read;
+		spinand->fact_otp = &table[i].fact_otp;
+		spinand->user_otp = &table[i].user_otp;
 
 		op = spinand_select_op_variant(spinand,
 					       info->op_variants.read_cache);
@@ -1494,6 +1496,12 @@ static int spinand_init(struct spinand_device *spinand)
 	mtd->_max_bad_blocks = nanddev_mtd_max_bad_blocks;
 	mtd->_resume = spinand_mtd_resume;
 
+	if (spinand_user_otp_size(spinand) || spinand_fact_otp_size(spinand)) {
+		ret = spinand_set_mtd_otp_ops(spinand);
+		if (ret)
+			goto err_cleanup_ecc_engine;
+	}
+
 	if (nand->ecc.engine) {
 		ret = mtd_ooblayout_count_freebytes(mtd);
 		if (ret < 0)

drivers/mtd/nand/spi/otp.c

@@ -0,0 +1,244 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2025, SaluteDevices. All Rights Reserved.
+ *
+ * Author: Martin Kurbanov <mmkurbanov@salutedevices.com>
+ */
+
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/spinand.h>
+
+static size_t spinand_otp_size(struct spinand_device *spinand,
+			       const struct spinand_otp_layout *layout)
+{
+	struct nand_device *nand = spinand_to_nand(spinand);
+	size_t otp_pagesize = nanddev_page_size(nand) +
+			      nanddev_per_page_oobsize(nand);
+
+	return layout->npages * otp_pagesize;
+}
+
+/**
+ * spinand_fact_otp_size() - Get SPI-NAND factory OTP area size
+ * @spinand: the spinand device
+ *
+ * Return: the OTP size.
+ */
+size_t spinand_fact_otp_size(struct spinand_device *spinand)
+{
+	return spinand_otp_size(spinand, &spinand->fact_otp->layout);
+}
+
+/**
+ * spinand_user_otp_size() - Get SPI-NAND user OTP area size
+ * @spinand: the spinand device
+ *
+ * Return: the OTP size.
+ */
+size_t spinand_user_otp_size(struct spinand_device *spinand)
+{
+	return spinand_otp_size(spinand, &spinand->user_otp->layout);
+}
+
+static int spinand_otp_check_bounds(struct spinand_device *spinand, loff_t ofs,
+				    size_t len,
+				    const struct spinand_otp_layout *layout)
+{
+	if (ofs < 0 || ofs + len > spinand_otp_size(spinand, layout))
+		return -EINVAL;
+
+	return 0;
+}
+
+static int spinand_user_otp_check_bounds(struct spinand_device *spinand,
+					 loff_t ofs, size_t len)
+{
+	return spinand_otp_check_bounds(spinand, ofs, len,
+					&spinand->user_otp->layout);
+}
+
+static int spinand_mtd_otp_info(struct mtd_info *mtd, size_t len,
+				size_t *retlen, struct otp_info *buf,
+				bool is_fact)
+{
+	struct spinand_device *spinand = mtd_to_spinand(mtd);
+	int ret;
+
+	*retlen = 0;
+
+	mutex_lock(&spinand->lock);
+
+	if (is_fact)
+		ret = spinand->fact_otp->ops->info(spinand, len, buf, retlen);
+	else
+		ret = spinand->user_otp->ops->info(spinand, len, buf, retlen);
+
+	mutex_unlock(&spinand->lock);
+
+	return ret;
+}
+
+static int spinand_mtd_fact_otp_info(struct mtd_info *mtd, size_t len,
+				     size_t *retlen, struct otp_info *buf)
+{
+	return spinand_mtd_otp_info(mtd, len, retlen, buf, true);
+}
+
+static int spinand_mtd_user_otp_info(struct mtd_info *mtd, size_t len,
+				     size_t *retlen, struct otp_info *buf)
+{
+	return spinand_mtd_otp_info(mtd, len, retlen, buf, false);
+}
+
+static int spinand_mtd_otp_read(struct mtd_info *mtd, loff_t ofs, size_t len,
+				size_t *retlen, u8 *buf, bool is_fact)
+{
+	struct spinand_device *spinand = mtd_to_spinand(mtd);
+	int ret;
+
+	*retlen = 0;
+
+	if (!len)
+		return 0;
+
+	ret = spinand_otp_check_bounds(spinand, ofs, len,
+				       is_fact ? &spinand->fact_otp->layout :
+						 &spinand->user_otp->layout);
+	if (ret)
+		return ret;
+
+	mutex_lock(&spinand->lock);
+
+	if (is_fact)
+		ret = spinand->fact_otp->ops->read(spinand, ofs, len, retlen,
+						   buf);
+	else
+		ret = spinand->user_otp->ops->read(spinand, ofs, len, retlen,
+						   buf);
+
+	mutex_unlock(&spinand->lock);
+
+	return ret;
+}
+
+static int spinand_mtd_fact_otp_read(struct mtd_info *mtd, loff_t ofs,
+				     size_t len, size_t *retlen, u8 *buf)
+{
+	return spinand_mtd_otp_read(mtd, ofs, len, retlen, buf, true);
+}
+
+static int spinand_mtd_user_otp_read(struct mtd_info *mtd, loff_t ofs,
+				     size_t len, size_t *retlen, u8 *buf)
+{
+	return spinand_mtd_otp_read(mtd, ofs, len, retlen, buf, false);
+}
+
+static int spinand_mtd_user_otp_write(struct mtd_info *mtd, loff_t ofs,
+				      size_t len, size_t *retlen, const u8 *buf)
+{
+	struct spinand_device *spinand = mtd_to_spinand(mtd);
+	const struct spinand_user_otp_ops *ops = spinand->user_otp->ops;
+	int ret;
+
+	*retlen = 0;
+
+	if (!len)
+		return 0;
+
+	ret = spinand_user_otp_check_bounds(spinand, ofs, len);
+	if (ret)
+		return ret;
+
+	mutex_lock(&spinand->lock);
+	ret = ops->write(spinand, ofs, len, retlen, buf);
+	mutex_unlock(&spinand->lock);
+
+	return ret;
+}
+
+static int spinand_mtd_user_otp_erase(struct mtd_info *mtd, loff_t ofs,
+				      size_t len)
+{
+	struct spinand_device *spinand = mtd_to_spinand(mtd);
+	const struct spinand_user_otp_ops *ops = spinand->user_otp->ops;
+	int ret;
+
+	if (!len)
+		return 0;
+
+	ret = spinand_user_otp_check_bounds(spinand, ofs, len);
+	if (ret)
+		return ret;
+
+	mutex_lock(&spinand->lock);
+	ret = ops->erase(spinand, ofs, len);
+	mutex_unlock(&spinand->lock);
+
+	return ret;
+}
+
+static int spinand_mtd_user_otp_lock(struct mtd_info *mtd, loff_t ofs,
+				     size_t len)
+{
+	struct spinand_device *spinand = mtd_to_spinand(mtd);
+	const struct spinand_user_otp_ops *ops = spinand->user_otp->ops;
+	int ret;
+
+	if (!len)
+		return 0;
+
+	ret = spinand_user_otp_check_bounds(spinand, ofs, len);
+	if (ret)
+		return ret;
+
+	mutex_lock(&spinand->lock);
+	ret = ops->lock(spinand, ofs, len);
+	mutex_unlock(&spinand->lock);
+
+	return ret;
+}
+
+/**
+ * spinand_set_mtd_otp_ops() - Setup OTP methods
+ * @spinand: the spinand device
+ *
+ * Setup OTP methods.
+ *
+ * Return: 0 on success, a negative error code otherwise.
+ */
+int spinand_set_mtd_otp_ops(struct spinand_device *spinand)
+{
+	struct mtd_info *mtd = spinand_to_mtd(spinand);
+	const struct spinand_fact_otp_ops *fact_ops = spinand->fact_otp->ops;
+	const struct spinand_user_otp_ops *user_ops = spinand->user_otp->ops;
+
+	if (!user_ops && !fact_ops)
+		return -EINVAL;
+
+	if (user_ops) {
+		if (user_ops->info)
+			mtd->_get_user_prot_info = spinand_mtd_user_otp_info;
+
+		if (user_ops->read)
+			mtd->_read_user_prot_reg = spinand_mtd_user_otp_read;
+
+		if (user_ops->write)
+			mtd->_write_user_prot_reg = spinand_mtd_user_otp_write;
+
+		if (user_ops->lock)
+			mtd->_lock_user_prot_reg = spinand_mtd_user_otp_lock;
+
+		if (user_ops->erase)
+			mtd->_erase_user_prot_reg = spinand_mtd_user_otp_erase;
+	}
+
+	if (fact_ops) {
+		if (fact_ops->info)
+			mtd->_get_fact_prot_info = spinand_mtd_fact_otp_info;
+
+		if (fact_ops->read)
+			mtd->_read_fact_prot_reg = spinand_mtd_fact_otp_read;
+	}
+
+	return 0;
+}