mtd: spi-nor: sst: Factor out common write operation to sst_nor_write_data()

Writing to the Flash in `sst_nor_write()` is a 3-step process:
first an optional one-byte write to get 2-byte-aligned, then the
bulk of the data is written out in vendor-specific 2-byte writes.
Finally, if there's a byte left over, another one-byte write.
This was implemented 3 times in the body of `sst_nor_write()`.
To reduce code duplication, factor out these sub-steps to their
own function.

Signed-off-by: Csókás, Bence <csokas.bence@prolan.hu>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
[pratyush@kernel.org: fixup whitespace, use %zu instead of %i in WARN()]
Signed-off-by: Pratyush Yadav <pratyush@kernel.org>
Link: https://lore.kernel.org/r/20240710091401.1282824-1-csokas.bence@prolan.hu

Author: Csókás, Bence

drivers/mtd/spi-nor/sst.c

@@ -167,6 +167,21 @@ static const struct flash_info sst_nor_parts[] = {
 	}
 };
 
+static int sst_nor_write_data(struct spi_nor *nor, loff_t to, size_t len,
+			      const u_char *buf)
+{
+	u8 op = (len == 1) ? SPINOR_OP_BP : SPINOR_OP_AAI_WP;
+	int ret;
+
+	nor->program_opcode = op;
+	ret = spi_nor_write_data(nor, to, 1, buf);
+	if (ret < 0)
+		return ret;
+	WARN(ret != len, "While writing %zu byte written %i bytes\n", len, ret);
+
+	return spi_nor_wait_till_ready(nor);
+}
+
 static int sst_nor_write(struct mtd_info *mtd, loff_t to, size_t len,
 			 size_t *retlen, const u_char *buf)
 {
@@ -188,33 +203,22 @@ static int sst_nor_write(struct mtd_info *mtd, loff_t to, size_t len,
 
 	/* Start write from odd address. */
 	if (to % 2) {
-		nor->program_opcode = SPINOR_OP_BP;
-
 		/* write one byte. */
-		ret = spi_nor_write_data(nor, to, 1, buf);
+		ret = sst_nor_write_data(nor, to, 1, buf);
 		if (ret < 0)
 			goto out;
-		WARN(ret != 1, "While writing 1 byte written %i bytes\n", ret);
-		ret = spi_nor_wait_till_ready(nor);
-		if (ret)
-			goto out;
 
 		to++;
 		actual++;
 	}
 
 	/* Write out most of the data here. */
 	for (; actual < len - 1; actual += 2) {
-		nor->program_opcode = SPINOR_OP_AAI_WP;
-
 		/* write two bytes. */
-		ret = spi_nor_write_data(nor, to, 2, buf + actual);
+		ret = sst_nor_write_data(nor, to, 2, buf + actual);
 		if (ret < 0)
 			goto out;
-		WARN(ret != 2, "While writing 2 bytes written %i bytes\n", ret);
-		ret = spi_nor_wait_till_ready(nor);
-		if (ret)
-			goto out;
+
 		to += 2;
 		nor->sst_write_second = true;
 	}
@@ -234,14 +238,9 @@ static int sst_nor_write(struct mtd_info *mtd, loff_t to, size_t len,
 		if (ret)
 			goto out;
 
-		nor->program_opcode = SPINOR_OP_BP;
-		ret = spi_nor_write_data(nor, to, 1, buf + actual);
+		ret = sst_nor_write_data(nor, to, 1, buf + actual);
 		if (ret < 0)
 			goto out;
-		WARN(ret != 1, "While writing 1 byte written %i bytes\n", ret);
-		ret = spi_nor_wait_till_ready(nor);
-		if (ret)
-			goto out;
 
 		actual += 1;