[PATCH 2/2] mtd: spi-nor: Always use biggest erase size

["Sverdlin, Alexander (Nokia - DE/Ulm)" <alexander.sverdlin@xxxxxxxxx>]

Optimize erase time by always using biggest erase size for given erase
request. Do it by removing "sector"-at-a-time erase code.
spi_nor_erase_multi_sectors() seems to be mature enough to handle all
the cases better.

For the above to work backwards-compatible regarding 4-bytes commands
spi_nor_set_4byte_opcodes() has to prepare them always, independent of
spi_nor_has_uniform_erase() flag.

Remainder check in spi_nor_erase() becomes superfluous because
spi_nor_erase_multi_sectors() performs it anyway.

The trigger for this change was n25q128a13: enabling SECT_4K increased
erase time of 128k block from 1.763s to 11.335s.

Fixes: 4607777c71 ("mtd: spi-nor: add subsector flag to n25q128a")
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx>
---
 drivers/mtd/spi-nor/spi-nor.c | 46 ++++++-----------------------------
 1 file changed, 7 insertions(+), 39 deletions(-)

diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
index c3598f0571cc..a25324a52eae 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -434,6 +434,10 @@ static u8 spi_nor_convert_3to4_erase(u8 opcode)
 
 static void spi_nor_set_4byte_opcodes(struct spi_nor *nor)
 {
+	struct spi_nor_erase_map *map = &nor->erase_map;
+	struct spi_nor_erase_type *erase;
+	int i;
+
 	/* Do some manufacturer fixups first */
 	switch (JEDEC_MFR(nor->info)) {
 	case SNOR_MFR_SPANSION:
@@ -450,16 +454,9 @@ static void spi_nor_set_4byte_opcodes(struct spi_nor *nor)
 	nor->program_opcode = spi_nor_convert_3to4_program(nor->program_opcode);
 	nor->erase_opcode = spi_nor_convert_3to4_erase(nor->erase_opcode);
 
-	if (!spi_nor_has_uniform_erase(nor)) {
-		struct spi_nor_erase_map *map = &nor->erase_map;
-		struct spi_nor_erase_type *erase;
-		int i;
-
-		for (i = 0; i < SNOR_ERASE_TYPE_MAX; i++) {
-			erase = &map->erase_type[i];
-			erase->opcode =
-				spi_nor_convert_3to4_erase(erase->opcode);
-		}
+	for (i = 0; i < SNOR_ERASE_TYPE_MAX; i++) {
+		erase = &map->erase_type[i];
+		erase->opcode = spi_nor_convert_3to4_erase(erase->opcode);
 	}
 }
 
@@ -978,18 +975,11 @@ static int spi_nor_erase(struct mtd_info *mtd, struct erase_info *instr)
 {
 	struct spi_nor *nor = mtd_to_spi_nor(mtd);
 	u32 addr, len;
-	uint32_t rem;
 	int ret;
 
 	dev_dbg(nor->dev, "at 0x%llx, len %lld\n", (long long)instr->addr,
 			(long long)instr->len);
 
-	if (spi_nor_has_uniform_erase(nor)) {
-		div_u64_rem(instr->len, mtd->erasesize, &rem);
-		if (rem)
-			return -EINVAL;
-	}
-
 	addr = instr->addr;
 	len = instr->len;
 
@@ -1021,28 +1011,6 @@ static int spi_nor_erase(struct mtd_info *mtd, struct erase_info *instr)
 		if (ret)
 			goto erase_err;
 
-	/* REVISIT in some cases we could speed up erasing large regions
-	 * by using SPINOR_OP_SE instead of SPINOR_OP_BE_4K.  We may have set up
-	 * to use "small sector erase", but that's not always optimal.
-	 */
-
-	/* "sector"-at-a-time erase */
-	} else if (spi_nor_has_uniform_erase(nor)) {
-		while (len) {
-			write_enable(nor);
-
-			ret = spi_nor_erase_sector(nor, addr);
-			if (ret)
-				goto erase_err;
-
-			addr += mtd->erasesize;
-			len -= mtd->erasesize;
-
-			ret = spi_nor_wait_till_ready(nor);
-			if (ret)
-				goto erase_err;
-		}
-
 	/* erase multiple sectors */
 	} else {
 		ret = spi_nor_erase_multi_sectors(nor, addr, len);
-- 
2.19.2


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