[PATCH v3 2/2] mtd: spi-nor: sst: Add support for Global Unlock on sst26vf

[Tudor Ambarus]

Even if sst26vf shares the SPINOR_OP_GBULK opcode with
Macronix (ex. MX25U12835F) and Winbound (ex. W25Q128FV),
it has its own Individual Block Protection scheme, which
is also capable to read-lock individual parameter blocks.
Thus the sst26vf's Individual Block Protection scheme will
reside in the sst.c manufacturer driver.

Add support to unlock the entire flash memory. The device
is write-protected by default after a power-on reset cycle
(volatile software protection), in order to avoid inadvertent
writes during power-up. Could do an erase, write, read back,
and compare when MTD_SPI_NOR_SWP_DISABLE_ON_VOLATILE=y.

Signed-off-by: Tudor Ambarus <tudor.ambarus at microchip.com>
---
v3:
- s/Winbound/Winbond/
- read CR.BPNV and check if we can really unlock the entire flash array
- sst26vf_unlock: return -EINVAL instead of -EOPNOTSUPP when caller
asks to unlock a range/granularity that we can't unlock

v2: v2: s/!ofs/ofs == 0/

 drivers/mtd/spi-nor/core.c |  2 +-
 drivers/mtd/spi-nor/core.h |  1 +
 drivers/mtd/spi-nor/sst.c  | 52 ++++++++++++++++++++++++++++++++++++--
 3 files changed, 52 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
index e82732dd31e1..c50b30fbb912 100644
--- a/drivers/mtd/spi-nor/core.c
+++ b/drivers/mtd/spi-nor/core.c
@@ -465,7 +465,7 @@ static int spi_nor_read_fsr(struct spi_nor *nor, u8 *fsr)
  *
  * Return: 0 on success, -errno otherwise.
  */
-static int spi_nor_read_cr(struct spi_nor *nor, u8 *cr)
+int spi_nor_read_cr(struct spi_nor *nor, u8 *cr)
 {
 	int ret;
 
diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
index eb26796db026..4a3f7f150b5d 100644
--- a/drivers/mtd/spi-nor/core.h
+++ b/drivers/mtd/spi-nor/core.h
@@ -441,6 +441,7 @@ int spi_nor_sr1_bit6_quad_enable(struct spi_nor *nor);
 int spi_nor_sr2_bit1_quad_enable(struct spi_nor *nor);
 int spi_nor_sr2_bit7_quad_enable(struct spi_nor *nor);
 int spi_nor_read_sr(struct spi_nor *nor, u8 *sr);
+int spi_nor_read_cr(struct spi_nor *nor, u8 *cr);
 int spi_nor_write_sr(struct spi_nor *nor, const u8 *sr, size_t len);
 int spi_nor_write_sr_and_check(struct spi_nor *nor, u8 sr1);
 
diff --git a/drivers/mtd/spi-nor/sst.c b/drivers/mtd/spi-nor/sst.c
index 00e48da0744a..980f4c09c91d 100644
--- a/drivers/mtd/spi-nor/sst.c
+++ b/drivers/mtd/spi-nor/sst.c
@@ -8,6 +8,53 @@
 
 #include "core.h"
 
+#define SST26VF_CR_BPNV		BIT(3)
+
+static int sst26vf_lock(struct spi_nor *nor, loff_t ofs, uint64_t len)
+{
+	return -EOPNOTSUPP;
+}
+
+static int sst26vf_unlock(struct spi_nor *nor, loff_t ofs, uint64_t len)
+{
+	int ret;
+
+	/* We only support unlocking the entire flash array. */
+	if (ofs != 0 || len != nor->params->size)
+		return -EINVAL;
+
+	ret = spi_nor_read_cr(nor, nor->bouncebuf);
+	if (ret)
+		return ret;
+
+	if (!(nor->bouncebuf[0] & SST26VF_CR_BPNV)) {
+		dev_dbg(nor->dev, "Any block has been permanently locked\n");
+		return -EINVAL;
+	}
+
+	return spi_nor_global_block_unlock(nor);
+}
+
+static int sst26vf_is_locked(struct spi_nor *nor, loff_t ofs, uint64_t len)
+{
+	return -EOPNOTSUPP;
+}
+
+static const struct spi_nor_locking_ops sst26vf_locking_ops = {
+	.lock = sst26vf_lock,
+	.unlock = sst26vf_unlock,
+	.is_locked = sst26vf_is_locked,
+};
+
+static void sst26vf_default_init(struct spi_nor *nor)
+{
+	nor->params->locking_ops = &sst26vf_locking_ops;
+}
+
+static const struct spi_nor_fixups sst26vf_fixups = {
+	.default_init = sst26vf_default_init,
+};
+
 static const struct flash_info sst_parts[] = {
 	/* SST -- large erase sizes are "overlays", "sectors" are 4K */
 	{ "sst25vf040b", INFO(0xbf258d, 0, 64 * 1024,  8,
@@ -39,8 +86,9 @@ static const struct flash_info sst_parts[] = {
 	{ "sst26vf016b", INFO(0xbf2641, 0, 64 * 1024, 32,
 			      SECT_4K | SPI_NOR_DUAL_READ) },
 	{ "sst26vf064b", INFO(0xbf2643, 0, 64 * 1024, 128,
-			      SECT_4K | SPI_NOR_DUAL_READ |
-			      SPI_NOR_QUAD_READ) },
+			      SECT_4K | SPI_NOR_DUAL_READ | SPI_NOR_QUAD_READ |
+			      SPI_NOR_HAS_LOCK | SPI_NOR_SWP_IS_VOLATILE)
+		.fixups = &sst26vf_fixups },
 };
 
 static int sst_write(struct mtd_info *mtd, loff_t to, size_t len,
-- 
2.25.1