[PATCH] mtd: spi-nor: swp: check SR_TB flag when getting tb_mask

[Shiji Yang]

When the chip does not support top/bottom block protect, the tb_mask
must be set to 0, otherwise SR1 bit5 will be unexpectedly modified.

Signed-off-by: Shiji Yang <yangshiji66 at outlook.com>
---
 drivers/mtd/spi-nor/swp.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/spi-nor/swp.c b/drivers/mtd/spi-nor/swp.c
index 9b07f83ae..e67a81dbb 100644
--- a/drivers/mtd/spi-nor/swp.c
+++ b/drivers/mtd/spi-nor/swp.c
@@ -28,8 +28,10 @@ static u8 spi_nor_get_sr_tb_mask(struct spi_nor *nor)
 {
 	if (nor->flags & SNOR_F_HAS_SR_TB_BIT6)
 		return SR_TB_BIT6;
-	else
+	else if (nor->flags & SNOR_F_HAS_SR_TB)
 		return SR_TB_BIT5;
+	else
+		return 0;
 }
 
 static u64 spi_nor_get_min_prot_length_sr(struct spi_nor *nor)
-- 
2.51.0