[PATCH v3 2/5] mtd: spi-nor: Set all BP bits to one when lock_len == mtd->size

[<Tudor.Ambarus@microchip.com>]

From: Tudor Ambarus <tudor.ambarus@microchip.com>

When there are more BP settings than needed for defining the protected
areas of the flash memory, most flashes will define the remaining
settings as "protect all", i.e. the equivalent of having all the BP bits
set to one. But there are flashes where the in-between BP values
are undefined (not mentioned), and only the "all bits set" is protecting
the entire memory. One such example is w25q80, where BP[2:0]=0b101 and
0b110 are not defined.

Set all the BP bits to one when lock_len == mtd->size, to treat this
special case.

Suggested-by: Michael Walle <michael@walle.cc>
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
---
 drivers/mtd/spi-nor/core.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
index 36660068bc04..3788a95c0a47 100644
--- a/drivers/mtd/spi-nor/core.c
+++ b/drivers/mtd/spi-nor/core.c
@@ -1660,13 +1660,19 @@ static int spi_nor_sr_lock(struct spi_nor *nor, loff_t ofs, uint64_t len)
 	 *
 	 *   pow = ceil(log2(size / len)) = log2(size) - floor(log2(len)) + 1
 	 */
-	pow = ilog2(mtd->size) - ilog2(lock_len) + 1;
-	val = mask - (pow << SR_BP_SHIFT);
-	if (val & ~mask)
-		return -EINVAL;
-	/* Don't "lock" with no region! */
-	if (!(val & mask))
-		return -EINVAL;
+	if (lock_len == mtd->size) {
+		val = mask;
+	} else {
+		pow = ilog2(mtd->size) - ilog2(lock_len) + 1;
+		val = mask - (pow << SR_BP_SHIFT);
+
+		if (val & ~mask)
+			return -EINVAL;
+
+		/* Don't "lock" with no region! */
+		if (!(val & mask))
+			return -EINVAL;
+	}
 
 	status_new = (status_old & ~mask & ~tb_mask) | val;
 
-- 
2.23.0

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