From: Quanyang Wang <[email protected]>

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 <[email protected]>
---
 drivers/mtd/spi-nor/core.c | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
index 33433c3ed995d..944499999ecca 100644
--- a/drivers/mtd/spi-nor/core.c
+++ b/drivers/mtd/spi-nor/core.c
@@ -1773,6 +1773,26 @@ static int spi_nor_is_unlocked_sr(struct spi_nor *nor, 
loff_t ofs, uint64_t len,
        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
@@ -1917,12 +1937,13 @@ 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

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