[PATCH 1/2] mtd: spi-nor: add unlock all config option

[Michael Walle <michael@walle.cc>]

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 at 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>
---
 drivers/mtd/spi/Kconfig        | 10 ++++++++++
 drivers/mtd/spi/spi-nor-core.c |  9 +++++----
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/spi/Kconfig b/drivers/mtd/spi/Kconfig
index 018e8c597e..bb8e8a9153 100644
--- 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 e16b0e1462..ef426dac02 100644
--- 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);
-- 
2.20.1