The locking scheme for ISSI devices is based on stm_lock mechanism. The is25xxxxx devices have 4 bits for selecting the range of blocks to be locked for write.
The current implementation, blocks entire 512 blocks of flash memory. Signed-off-by: Sagar Shrikant Kadam <[email protected]> --- drivers/mtd/spi-nor/spi-nor.c | 60 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 60 insertions(+) diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c index 81c7b3e..2dba7e9 100644 --- a/drivers/mtd/spi-nor/spi-nor.c +++ b/drivers/mtd/spi-nor/spi-nor.c @@ -1459,6 +1459,65 @@ static int macronix_quad_enable(struct spi_nor *nor) return 0; } +/** + * Lock a region of the flash.Implementation is based on stm_lock + * Supports the block protection bits BP{0,1,2,3} in the status register + * Returns negative on errors, 0 on success. + */ +static int issi_lock(struct spi_nor *nor, loff_t ofs, uint64_t len) +{ + struct mtd_info *mtd = &nor->mtd; + int status_old, status_new; + u8 mask = SR_BP3 | SR_BP2 | SR_BP1 | SR_BP0; + u8 shift = ffs(mask) - 1, pow, val = 0; + loff_t lock_len; + bool use_top = true; + + status_old = read_sr(nor); + + if (status_old < 0) + return status_old; + + /* lock_len: length of region that should end up locked */ + if (use_top) + lock_len = mtd->size - ofs; + else + lock_len = ofs + len; + + /* + * Need smallest pow such that: + * + * 1 / (2^pow) <= (len / size) + * + * so (assuming power-of-2 size) we do: + * + * pow = ceil(log2(size / len)) = log2(size) - floor(log2(len)) + */ + pow = ilog2(mtd->size) - ilog2(lock_len); + val = mask - (pow << shift); + + if (val & ~mask) + return -EINVAL; + + /* Don't "lock" with no region! */ + if (!(val & mask)) + return -EINVAL; + + status_new = (status_old & ~mask & ~SR_TB) | val; + + /* Disallow further writes if WP pin is asserted */ + status_new |= SR_SRWD; + + /* Don't bother if they're the same */ + if (status_new == status_old) + return 0; + + /* Only modify protection if it will not unlock other areas */ + if ((status_new & mask) < (status_old & mask)) + return -EINVAL; + + return write_sr_and_check(nor, status_new, mask); +} /** * issi_unlock() - clear BP[0123] write-protection. @@ -4121,6 +4180,7 @@ int spi_nor_scan(struct spi_nor *nor, const char *name, /* NOR protection support for ISSI chips */ if (JEDEC_MFR(info) == SNOR_MFR_ISSI || info->flags & SPI_NOR_HAS_LOCK) { + nor->flash_lock = issi_lock; nor->flash_unlock = issi_unlock; } -- 1.9.1
