From c77e111b6d159a1df32c586dd61a11b00d54a10b Mon Sep 17 00:00:00 2001
From: Pratyush Yadav <p.yadav@ti.com>
Date: Thu, 8 Jun 2023 16:29:31 +0530
Subject: [PATCH] mtd: spi-nor-core: Do not start or end writes at odd address
 in DTR mode

On DTR capable flashes like Micron Xcella the writes cannot start or end
at an odd address in DTR mode. Extra 0xff bytes need to be prepended or
appended respectively to make sure both the start and end addresses are
even.

Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
Reviewed-by: Vignesh Raghavendra <vigneshr@ti.com>
Signed-off-by: Apurva Nandan <a-nandan@ti.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
---
 drivers/mtd/spi/spi-nor-core.c | 59 +++++++++++++++++++++++++++++++---
 1 file changed, 55 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/spi/spi-nor-core.c b/drivers/mtd/spi/spi-nor-core.c
index 35ab608863..232a0ac3a9 100644
--- a/drivers/mtd/spi/spi-nor-core.c
+++ b/drivers/mtd/spi/spi-nor-core.c
@@ -1760,11 +1760,62 @@ static int spi_nor_write(struct mtd_info *mtd, loff_t to, size_t len,
 		if (ret < 0)
 			return ret;
 #endif
+
 		write_enable(nor);
-		ret = nor->write(nor, addr, page_remain, buf + i);
-		if (ret < 0)
-			goto write_err;
-		written = ret;
+
+		/*
+		 * On DTR capable flashes like Micron Xcella the writes cannot
+		 * start or end at an odd address in DTR mode. So we need to
+		 * append or prepend extra 0xff bytes to make sure the start
+		 * address and end address are even.
+		 */
+		if (spi_nor_protocol_is_dtr(nor->write_proto) &&
+		    ((addr | page_remain) & 1)) {
+			u_char *tmp;
+			size_t extra_bytes = 0;
+
+			tmp = kmalloc(nor->page_size, 0);
+			if (!tmp) {
+				ret = -ENOMEM;
+				goto write_err;
+			}
+
+			/* Prepend a 0xff byte if the start address is odd. */
+			if (addr & 1) {
+				tmp[0] = 0xff;
+				memcpy(tmp + 1, buf + i, page_remain);
+				addr--;
+				page_remain++;
+				extra_bytes++;
+			} else {
+				memcpy(tmp, buf + i, page_remain);
+			}
+
+			/* Append a 0xff byte if the end address is odd. */
+			if ((addr + page_remain) & 1) {
+				tmp[page_remain + extra_bytes] = 0xff;
+				extra_bytes++;
+				page_remain++;
+			}
+
+			ret = nor->write(nor, addr, page_remain, tmp);
+
+			kfree(tmp);
+
+			if (ret < 0)
+				goto write_err;
+
+			/*
+			 * We write extra bytes but they are not part of the
+			 * original write.
+			 */
+			written = ret - extra_bytes;
+		} else {
+			ret = nor->write(nor, addr, page_remain, buf + i);
+			if (ret < 0)
+				goto write_err;
+			written = ret;
+		}
 
 		ret = spi_nor_wait_till_ready(nor);
 		if (ret)