[PATCH 2/2] mtd: spi-nor: add option to keep lock bits

[Michael Walle <michael@walle.cc>]

Traditionally, linux unlocks the whole flash because there are legacy
devices which has the write protections bits set by default at startup.
If you actually want to use the flash protection bits, eg. because there
is a read-only part for a bootloader, this automatic unlocking is
harmful. If there is no hardware write protection in place (usually
called WP#), a startup of the kernel just discards this protection.

Introduce a new device tree flag to indicate that the flash should not
be automatically unlocked.

Signed-off-by: Michael Walle <michael@walle.cc>
---
 drivers/mtd/spi-nor/spi-nor.c | 5 ++++-
 include/linux/mtd/spi-nor.h   | 1 +
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
index f4afe123e9dc..d0bec0adf2f8 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -4910,7 +4910,7 @@ static int spi_nor_quad_enable(struct spi_nor *nor)
  */
 static int spi_nor_unlock_all(struct spi_nor *nor)
 {
-	if (nor->flags & SNOR_F_HAS_LOCK)
+	if (nor->flags & SNOR_F_HAS_LOCK && !(nor->flags & SNOR_F_NO_UNLOCK))
 		return spi_nor_unlock(&nor->mtd, 0, nor->params.size);
 
 	return 0;
@@ -5159,6 +5159,9 @@ int spi_nor_scan(struct spi_nor *nor, const char *name,
 	if (of_property_read_bool(np, "broken-flash-reset"))
 		nor->flags |= SNOR_F_BROKEN_RESET;
 
+	if (of_property_read_bool(np, "no-unlock"))
+		nor->flags |= SNOR_F_NO_UNLOCK;
+
 	/*
 	 * Configure the SPI memory:
 	 * - select op codes for (Fast) Read, Page Program and Sector Erase.
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index 5a4623fc586b..4cba5dda2d38 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -244,6 +244,7 @@ enum spi_nor_option_flags {
 	SNOR_F_HAS_LOCK		= BIT(8),
 	SNOR_F_HAS_16BIT_SR	= BIT(9),
 	SNOR_F_NO_READ_CR	= BIT(10),
+	SNOR_F_NO_UNLOCK	= BIT(11),
 
 };
 
-- 
2.20.1