mtd: spi-nor: factor out write_enable() for erase commands

write_enable() was being duplicated to both m25p80.c and fsl-quadspi.c.
But this should be handled within the spi-nor abstraction layer.

At the same time, let's add write_disable() after erasing, so we don't
leave the flash in a write-enabled state afterward.
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Acked-by: Huang Shijie <shijie.huang@intel.com>

drivers/mtd/devices/m25p80.c

@@ -157,16 +157,10 @@ static int m25p80_read(struct spi_nor *nor, loff_t from, size_t len,
 static int m25p80_erase(struct spi_nor *nor, loff_t offset)
 {
 	struct m25p *flash = nor->priv;
-	int ret;
 
 	dev_dbg(nor->dev, "%dKiB at 0x%08x\n",
 		flash->mtd.erasesize / 1024, (u32)offset);
 
-	/* Send write enable, then erase commands. */
-	ret = nor->write_reg(nor, SPINOR_OP_WREN, NULL, 0, 0);
-	if (ret)
-		return ret;
-
 	/* Set up command buffer. */
 	flash->command[0] = nor->erase_opcode;
 	m25p_addr2cmd(nor, offset, flash->command);

drivers/mtd/spi-nor/fsl-quadspi.c

@@ -738,11 +738,6 @@ static int fsl_qspi_erase(struct spi_nor *nor, loff_t offs)
 	dev_dbg(nor->dev, "%dKiB at 0x%08x:0x%08x\n",
 		nor->mtd->erasesize / 1024, q->chip_base_addr, (u32)offs);
 
-	/* Send write enable, then erase commands. */
-	ret = nor->write_reg(nor, SPINOR_OP_WREN, NULL, 0, 0);
-	if (ret)
-		return ret;
-
 	ret = fsl_qspi_runcmd(q, nor->erase_opcode, offs, 0);
 	if (ret)
 		return ret;

drivers/mtd/spi-nor/spi-nor.c

@@ -265,9 +265,6 @@ static int erase_chip(struct spi_nor *nor)
 {
 	dev_dbg(nor->dev, " %lldKiB\n", (long long)(nor->mtd->size >> 10));
 
-	/* Send write enable, then erase commands. */
-	write_enable(nor);
-
 	return nor->write_reg(nor, SPINOR_OP_CHIP_ERASE, NULL, 0, 0);
 }
 
@@ -322,6 +319,8 @@ static int spi_nor_erase(struct mtd_info *mtd, struct erase_info *instr)
 
 	/* whole-chip erase? */
 	if (len == mtd->size) {
+		write_enable(nor);
+
 		if (erase_chip(nor)) {
 			ret = -EIO;
 			goto erase_err;
@@ -339,6 +338,8 @@ static int spi_nor_erase(struct mtd_info *mtd, struct erase_info *instr)
 	/* "sector"-at-a-time erase */
 	} else {
 		while (len) {
+			write_enable(nor);
+
 			if (nor->erase(nor, addr)) {
 				ret = -EIO;
 				goto erase_err;
@@ -353,6 +354,8 @@ static int spi_nor_erase(struct mtd_info *mtd, struct erase_info *instr)
 		}
 	}
 
+	write_disable(nor);
+
 	spi_nor_unlock_and_unprep(nor, SPI_NOR_OPS_ERASE);
 
 	instr->state = MTD_ERASE_DONE;