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Subject[PATCH v8 3/4] mtd: spi-nor: add support to unlock the 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].
Add an identifier within the flash info structure to indicate that a
particular flash device has the fourth block protect bit (SPI_NOR_HAS_BP3).

Increase size of flash_info flags from u16 to u32 to avoid flag overflow
due SPI_NOR_HAS_BP3.
Clear block protection bits unlocks the flash memory regions.

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

spell correction: "Configuration" in spansion_quad_enable function
description.

Signed-off-by: Sagar Shrikant Kadam <sagar.kadam@sifive.com>
---
drivers/mtd/spi-nor/spi-nor.c | 72 ++++++++++++++++++++++++++++++++++++++++---
include/linux/mtd/spi-nor.h | 2 ++
2 files changed, 70 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
index cb40b1b..24c1c11 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -250,7 +250,7 @@ struct flash_info {
u16 page_size;
u16 addr_width;

- u16 flags;
+ u32 flags;
#define SECT_4K BIT(0) /* SPINOR_OP_BE_4K works uniformly */
#define SPI_NOR_NO_ERASE BIT(1) /* No erase command needed */
#define SST_WRITE BIT(2) /* use SST byte programming */
@@ -279,6 +279,13 @@ struct flash_info {
#define SPI_NOR_SKIP_SFDP BIT(13) /* Skip parsing of SFDP tables */
#define USE_CLSR BIT(14) /* use CLSR command */
#define SPI_NOR_OCTAL_READ BIT(15) /* Flash supports Octal Read */
+#define SPI_NOR_HAS_BP3 BIT(16) /*
+ * Flash SR has block protect bits
+ * for lock/unlock purpose, few support
+ * BP0-BP2 while few support BP0-BP3.
+ * This flag identifies devices that
+ * support BP3 bit.
+ */

/* Part specific fixup hooks. */
const struct spi_nor_fixups *fixups;
@@ -1461,7 +1468,55 @@ static int macronix_quad_enable(struct spi_nor *nor)
}

/**
- * spansion_quad_enable() - set QE bit in Configuraiton Register.
+ * 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;
+
+ if (nor->flags & SNOR_F_HAS_BP3)
+ mask = SR_BP3 | SR_BP2 | SR_BP1 | SR_BP0;
+ else
+ mask = SR_BP2 | SR_BP1 | SR_BP0;
+
+ 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 protect bits cleared SR: 0x%x\n",
+ ret);
+ ret = 0;
+ } else {
+ dev_err(nor->dev, "ISSI block protect bits not cleared\n");
+ ret = -EINVAL;
+ }
+ return ret;
+}
+
+/**
+ * spansion_quad_enable() - set QE bit in Configuration Register.
* @nor: pointer to a 'struct spi_nor'
*
* Set the Quad Enable (QE) bit in the Configuration Register.
@@ -1948,8 +2003,10 @@ static int spi_nor_spansion_clear_sr_bp(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)
- .fixups = &is25lp256_fixups },
+ SPI_NOR_4B_OPCODES | SPI_NOR_HAS_LOCK | SPI_NOR_HAS_TB |
+ SPI_NOR_HAS_BP3)
+ .fixups = &is25lp256_fixups
+ },
/* Macronix */
{ "mx25l512e", INFO(0xc22010, 0, 64 * 1024, 1, SECT_4K) },
{ "mx25l2005a", INFO(0xc22012, 0, 64 * 1024, 4, SECT_4K) },
@@ -4207,6 +4264,13 @@ 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 &&
+ info->flags & SPI_NOR_HAS_BP3) {
+ 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 5d6583e..4f92dbb 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 */
#define SR_TB BIT(5) /* Top/Bottom protect */
#define SR_SRWD BIT(7) /* SR write protect */
/* Spansion/Cypress specific status bits */
@@ -244,6 +245,7 @@ enum spi_nor_option_flags {
SNOR_F_BROKEN_RESET = BIT(6),
SNOR_F_4B_OPCODES = BIT(7),
SNOR_F_HAS_4BAIT = BIT(8),
+ SNOR_F_HAS_BP3 = BIT(9),
};

/**
--
1.9.1
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