mtd: spi-nor: add unlock all config option

Provide an explicit configuration option to disable default "unlock all"
of any flash chip which supports locking. It doesn't make sense to
automatically unprotect the entire flash on each u-boot startup if the
block protection bits are actually used.

Traditionally, the unlock was there to be able to write to flash devices
which powered-up with the block protection bits set. Over time this
feature creeped into all flash devices which support locking.

For a more detailed description and discussion see:
https://lore.kernel.org/linux-mtd/20201203162959.29589-8-michael@walle.cc/

Keep things simple in u-boot and just provide a configration option to
disable this behavior which can be set per board.

Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>

diff --git a/drivers/mtd/spi/Kconfig b/drivers/mtd/spi/Kconfig
index ea44443..f8db8e5 100644 (file)
--- a/drivers/mtd/spi/Kconfig
+++ b/drivers/mtd/spi/Kconfig
@@ -95,6 +95,16 @@ config SPI_FLASH_BAR
          Bank/Extended address registers are used to access the flash
          which has size > 16MiB in 3-byte addressing.
 
+config SPI_FLASH_UNLOCK_ALL
+       bool "Unlock the entire SPI flash on u-boot startup"
+       default y
+       help
+        Some flashes tend to power up with the software write protection
+        bits set. If this option is set, the whole flash will be unlocked.
+
+        For legacy reasons, this option default to y. But if you intend to
+        actually use the software protection bits you should say n here.
+
 config SF_DUAL_FLASH
        bool "SPI DUAL flash memory support"
        help

diff --git a/drivers/mtd/spi/spi-nor-core.c b/drivers/mtd/spi/spi-nor-core.c
index e16b0e1..ef426da 100644 (file)
--- a/drivers/mtd/spi/spi-nor-core.c
+++ b/drivers/mtd/spi/spi-nor-core.c
@@ -2443,10 +2443,11 @@ static int spi_nor_init(struct spi_nor *nor)
         * Atmel, SST, Intel/Numonyx, and others serial NOR tend to power up
         * with the software protection bits set
         */
-       if (JEDEC_MFR(nor->info) == SNOR_MFR_ATMEL ||
-           JEDEC_MFR(nor->info) == SNOR_MFR_INTEL ||
-           JEDEC_MFR(nor->info) == SNOR_MFR_SST ||
-           nor->info->flags & SPI_NOR_HAS_LOCK) {
+       if (IS_ENABLED(CONFIG_SPI_FLASH_UNLOCK_ALL) &&
+           (JEDEC_MFR(nor->info) == SNOR_MFR_ATMEL ||
+            JEDEC_MFR(nor->info) == SNOR_MFR_INTEL ||
+            JEDEC_MFR(nor->info) == SNOR_MFR_SST ||
+            nor->info->flags & SPI_NOR_HAS_LOCK)) {
                write_enable(nor);
                write_sr(nor, 0);
                spi_nor_wait_till_ready(nor);