mtd: spi-nor: implement OTP support for Winbond and similar flashes

Use the new OTP ops to implement OTP access on Winbond flashes. Most
Winbond flashes provides up to four different OTP regions ("Security
Registers").

Winbond devices use a special opcode to read and write to the OTP
regions, just like the RDSFDP opcode. In fact, it seems that the
(undocumented) first OTP area of the newer flashes is the actual SFDP
table.

On a side note, Winbond devices also allow erasing the OTP regions as
long as the area isn't locked down.

Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20210321235140.8308-3-michael@walle.cc

1 files changed, 164 insertions, 0 deletions

diff --git a/drivers/mtd/spi-nor/otp.c b/drivers/mtd/spi-nor/otp.c
index 075b7290a95d..5021d40dffbf 100644
--- a/drivers/mtd/spi-nor/otp.c
+++ b/drivers/mtd/spi-nor/otp.c
@@ -14,6 +14,170 @@
 #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 OTP data
+ * @nor:	pointer to 'struct spi_nor'
+ * @from:       offset to read from
+ * @len:        number of bytes to read
+ * @buf:        pointer to dst buffer
+ *
+ * Read OTP data from one region by using the SPINOR_OP_RSECR commands. This
+ * method is used on GigaDevice and Winbond flashes.
+ *
+ * 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->addr_width = 3;
+	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 OTP data
+ * @nor:        pointer to 'struct spi_nor'
+ * @to:         offset to write to
+ * @len:        number of bytes to write
+ * @buf:        pointer to src buffer
+ *
+ * Write OTP data to one region by using the SPINOR_OP_PSECR commands. This
+ * method is used on GigaDevice and Winbond flashes.
+ *
+ * Please note, the write must not span multiple OTP regions.
+ *
+ * Return: number of bytes written successfully, -errno otherwise
+ */
+int spi_nor_otp_write_secr(struct spi_nor *nor, loff_t addr, size_t len, 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->addr_width = 3;
+	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 OTP region.
+	 */
+	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;
+}
+
+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;