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Subject[PATCH v5 2/3] mtd: spi-nor: add support to unlock flash device
Date
Nor device (is25wp256 mounted on HiFive unleashed Rev A00 board) from ISSI
have memory blocks guarded by block protection bits BP[0,1,2,3].

Clearing block protection bits,unlocks the flash memory regions
The unlock scheme is registered during nor scans.

Based on code developed by Wesley Terpstra <wesley@sifive.com>
and/or Palmer Dabbelt <palmer@sifive.com>.
https://github.com/riscv/riscv-linux/commit/c94e267766d62bc9a669611c3d0c8ed5ea26569b

Signed-off-by: Sagar Shrikant Kadam <sagar.kadam@sifive.com>
---
drivers/mtd/spi-nor/spi-nor.c | 51 ++++++++++++++++++++++++++++++++++++++++++-
include/linux/mtd/spi-nor.h | 1 +
2 files changed, 51 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
index 2d5a925..b7c6261 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -1461,6 +1461,49 @@ static int macronix_quad_enable(struct spi_nor *nor)
}

/**
+ * issi_unlock() - clear BP[0123] write-protection.
+ * @nor: pointer to a 'struct spi_nor'.
+ * @ofs: offset from which to unlock memory.
+ * @len: number of bytes to unlock.
+ *
+ * Bits [2345] of the Status Register are BP[0123].
+ * ISSI chips use a different block protection scheme than other chips.
+ * Just disable the write-protect unilaterally.
+ *
+ * Return: 0 on success, -errno otherwise.
+ */
+static int issi_unlock(struct spi_nor *nor, loff_t ofs, uint64_t len)
+{
+ int ret, val;
+ u8 mask = SR_BP0 | SR_BP1 | SR_BP2 | SR_BP3;
+
+ val = read_sr(nor);
+ if (val < 0)
+ return val;
+ if (!(val & mask))
+ return 0;
+
+ write_enable(nor);
+
+ write_sr(nor, val & ~mask);
+
+ ret = spi_nor_wait_till_ready(nor);
+ if (ret)
+ return ret;
+
+ ret = read_sr(nor);
+ if (ret > 0 && !(ret & mask)) {
+ dev_info(nor->dev,
+ "ISSI Block Protection Bits cleared SR=0x%x", ret);
+ ret = 0;
+ } else {
+ dev_err(nor->dev, "ISSI Block Protection Bits not cleared\n");
+ ret = -EINVAL;
+ }
+ return ret;
+}
+
+/**
* spansion_quad_enable() - set QE bit in Configuraiton Register.
* @nor: pointer to a 'struct spi_nor'
*
@@ -1836,7 +1879,7 @@ static int sr2_bit7_quad_enable(struct spi_nor *nor)
SECT_4K | SPI_NOR_DUAL_READ | SPI_NOR_QUAD_READ) },
{ "is25wp256", INFO(0x9d7019, 0, 64 * 1024, 1024,
SECT_4K | SPI_NOR_DUAL_READ | SPI_NOR_QUAD_READ |
- SPI_NOR_4B_OPCODES)
+ SPI_NOR_4B_OPCODES | SPI_NOR_HAS_LOCK)
},

/* Macronix */
@@ -4080,6 +4123,12 @@ int spi_nor_scan(struct spi_nor *nor, const char *name,
nor->flash_is_locked = stm_is_locked;
}

+ /* NOR protection support for ISSI chips */
+ if (JEDEC_MFR(info) == SNOR_MFR_ISSI ||
+ info->flags & SPI_NOR_HAS_LOCK) {
+ nor->flash_unlock = issi_unlock;
+
+ }
if (nor->flash_lock && nor->flash_unlock && nor->flash_is_locked) {
mtd->_lock = spi_nor_lock;
mtd->_unlock = spi_nor_unlock;
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index ff13297..9a7d719 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -127,6 +127,7 @@
#define SR_BP0 BIT(2) /* Block protect 0 */
#define SR_BP1 BIT(3) /* Block protect 1 */
#define SR_BP2 BIT(4) /* Block protect 2 */
+#define SR_BP3 BIT(5) /* Block protect 3 for ISSI device*/
#define SR_TB BIT(5) /* Top/Bottom protect */
#define SR_SRWD BIT(7) /* SR write protect */
/* Spansion/Cypress specific status bits */
--
1.9.1
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