[PATCH v9 25/28] mtd: spi-nor-core: allow truncated erases

[Pratyush Yadav <p.yadav@ti.com>]

On devices with non-uniform sector sizes like Spansion S25 or S28 family
of flashes the sector under erase does not necessarily have to be
mtd->erasesize bytes long. For example, on S28 flashes the first 128 KiB
region is composed of 32 4 KiB sectors, then a 128 KiB sector, and then
256 KiB sectors till the end.

Let the flash-specific erase functions erase less than the requested
length in case of the 4 or 128 KiB sectors and report the number of
bytes erased back to the calling function.

Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
---
 drivers/mtd/spi/spi-nor-core.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/mtd/spi/spi-nor-core.c b/drivers/mtd/spi/spi-nor-core.c
index 0199352d31..a91a358560 100644
--- a/drivers/mtd/spi/spi-nor-core.c
+++ b/drivers/mtd/spi/spi-nor-core.c
@@ -806,7 +806,8 @@ static int read_bar(struct spi_nor *nor, const struct flash_info *info)
 #endif
 
 /*
- * Initiate the erasure of a single sector
+ * Initiate the erasure of a single sector. Returns the number of bytes erased
+ * on success, a negative error code on error.
  */
 static int spi_nor_erase_sector(struct spi_nor *nor, u32 addr)
 {
@@ -815,6 +816,7 @@ static int spi_nor_erase_sector(struct spi_nor *nor, u32 addr)
 			   SPI_MEM_OP_ADDR(nor->addr_width, addr, 0),
 			   SPI_MEM_OP_NO_DUMMY,
 			   SPI_MEM_OP_NO_DATA);
+	int ret;
 
 	spi_nor_setup_op(nor, &op, nor->write_proto);
 
@@ -825,7 +827,11 @@ static int spi_nor_erase_sector(struct spi_nor *nor, u32 addr)
 	 * Default implementation, if driver doesn't have a specialized HW
 	 * control
 	 */
-	return spi_mem_exec_op(nor->spi, &op);
+	ret = spi_mem_exec_op(nor->spi, &op);
+	if (ret)
+		return ret;
+
+	return nor->mtd.erasesize;
 }
 
 /*
@@ -861,11 +867,11 @@ static int spi_nor_erase(struct mtd_info *mtd, struct erase_info *instr)
 		write_enable(nor);
 
 		ret = spi_nor_erase_sector(nor, addr);
-		if (ret)
+		if (ret < 0)
 			goto erase_err;
 
-		addr += mtd->erasesize;
-		len -= mtd->erasesize;
+		addr += ret;
+		len -= ret;
 
 		ret = spi_nor_wait_till_ready(nor);
 		if (ret)
-- 
2.30.0