[PATCH] mtd: spi-nor: swp: fix unlock lower area failure

[quanyang.wang at windriver.com]

From: Quanyang Wang <quanyang.wang at windriver.com>

In the function spi_nor_sr_unlock, the variables "can_be_top" and
"can_be_bottom" determine how to calculate the value of "lock_len".

When we try to unlock a locked region in the lower area of flash,
the variables "can_be_top" and "can_be_bottom" may be all true and
this is not right because for this case "lock_len" is only "ofs"
but not "mtd->size - (ofs + len)".

So introduce spi_nor_is_lower_area() to check if the area to be
unlocked is in the lower and use it to exclude "can_be_top".

It's similar to spi_nor_is_upper_area() which is used to exclude
"can_be_bottom".

Signed-off-by: Quanyang Wang <quanyang.wang at windriver.com>
---
 drivers/mtd/spi-nor/swp.c | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/spi-nor/swp.c b/drivers/mtd/spi-nor/swp.c
index 63512ff3b184..3214b644f093 100644
--- a/drivers/mtd/spi-nor/swp.c
+++ b/drivers/mtd/spi-nor/swp.c
@@ -118,6 +118,26 @@ static bool spi_nor_is_unlocked_sr(struct spi_nor *nor, loff_t ofs,
 	return spi_nor_check_lock_status_sr(nor, ofs, len, sr, false);
 }
 
+static bool spi_nor_is_lower_area(struct spi_nor *nor, loff_t ofs, uint64_t len)
+{
+	struct mtd_info *mtd = &nor->mtd;
+
+	if (nor->flags & SNOR_F_HAS_SR_TB)
+		return ((ofs + len) <= (mtd->size >> 1));
+	else
+		return false;
+}
+
+static bool spi_nor_is_upper_area(struct spi_nor *nor, loff_t ofs, uint64_t len)
+{
+	struct mtd_info *mtd = &nor->mtd;
+
+	if ((nor->flags & SNOR_F_HAS_SR_TB))
+		return (ofs >= (mtd->size >> 1));
+	else
+		return true;
+}
+
 /*
  * Lock a region of the flash. Compatible with ST Micro and similar flash.
  * Supports the block protection bits BP{0,1,2}/BP{0,1,2,3} in the status
@@ -259,12 +279,13 @@ static int spi_nor_sr_unlock(struct spi_nor *nor, loff_t ofs, uint64_t len)
 		return 0;
 
 	/* If anything below us is locked, we can't use 'top' protection */
-	if (!spi_nor_is_unlocked_sr(nor, 0, ofs, status_old))
+	if ((!spi_nor_is_unlocked_sr(nor, 0, ofs, status_old)) ||
+				    spi_nor_is_lower_area(nor, ofs, len))
 		can_be_top = false;
 
 	/* If anything above us is locked, we can't use 'bottom' protection */
 	if (!spi_nor_is_unlocked_sr(nor, ofs + len, mtd->size - (ofs + len),
-				    status_old))
+				    status_old) || spi_nor_is_upper_area(nor, ofs, len))
 		can_be_bottom = false;
 
 	if (!can_be_bottom && !can_be_top)
-- 
2.25.1