mtd: spi-nor: otp: implement erase for Winbond and similar flashes

Winbond flashes with OTP support provide a command to erase the OTP
data. This might come in handy during development.

This was tested with a Winbond W25Q32JW on a LS1028A SoC with the
NXP FSPI controller.
Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Pratyush Yadav <p.yadav@ti.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>

drivers/mtd/spi-nor/core.c

@@ -1318,7 +1318,7 @@ static u32 spi_nor_convert_addr(struct spi_nor *nor, loff_t addr)
 /*
  * Initiate the erasure of a single sector
  */
-static int spi_nor_erase_sector(struct spi_nor *nor, u32 addr)
+int spi_nor_erase_sector(struct spi_nor *nor, u32 addr)
 {
 	int i;
 

drivers/mtd/spi-nor/core.h

@@ -207,6 +207,7 @@ struct spi_nor_otp_organization {
  * @read:	read from the SPI NOR OTP area.
  * @write:	write to the SPI NOR OTP area.
  * @lock:	lock an OTP region.
+ * @erase:	erase an OTP region.
  * @is_locked:	check if an OTP region of the SPI NOR is locked.
  */
 struct spi_nor_otp_ops {
@@ -214,6 +215,7 @@ struct spi_nor_otp_ops {
 	int (*write)(struct spi_nor *nor, loff_t addr, size_t len,
 		     const u8 *buf);
 	int (*lock)(struct spi_nor *nor, unsigned int region);
+	int (*erase)(struct spi_nor *nor, loff_t addr);
 	int (*is_locked)(struct spi_nor *nor, unsigned int region);
 };
 
@@ -503,10 +505,12 @@ ssize_t spi_nor_read_data(struct spi_nor *nor, loff_t from, size_t len,
 			  u8 *buf);
 ssize_t spi_nor_write_data(struct spi_nor *nor, loff_t to, size_t len,
 			   const u8 *buf);
+int spi_nor_erase_sector(struct spi_nor *nor, u32 addr);
 
 int spi_nor_otp_read_secr(struct spi_nor *nor, loff_t addr, size_t len, u8 *buf);
 int spi_nor_otp_write_secr(struct spi_nor *nor, loff_t addr, size_t len,
 			   const u8 *buf);
+int spi_nor_otp_erase_secr(struct spi_nor *nor, loff_t addr);
 int spi_nor_otp_lock_sr2(struct spi_nor *nor, unsigned int region);
 int spi_nor_otp_is_locked_sr2(struct spi_nor *nor, unsigned int region);
 

drivers/mtd/spi-nor/otp.c

@@ -120,6 +120,38 @@ int spi_nor_otp_write_secr(struct spi_nor *nor, loff_t addr, size_t len,
 	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 };
@@ -360,6 +392,59 @@ static int spi_nor_mtd_otp_write(struct mtd_info *mtd, loff_t to, size_t len,
 	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);
@@ -418,4 +503,5 @@ void spi_nor_otp_init(struct spi_nor *nor)
 	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;
 }

drivers/mtd/spi-nor/winbond.c

@@ -139,6 +139,7 @@ static int winbond_set_4byte_addr_mode(struct spi_nor *nor, bool enable)
 static const struct spi_nor_otp_ops winbond_otp_ops = {
 	.read = spi_nor_otp_read_secr,
 	.write = spi_nor_otp_write_secr,
+	.erase = spi_nor_otp_erase_secr,
 	.lock = spi_nor_otp_lock_sr2,
 	.is_locked = spi_nor_otp_is_locked_sr2,
 };