openwrt/target/linux/brcm63xx/patches-4.4/000-4.8-08-mtd-spi-nor-simplify-write-loop.patch

From e5d05cbd6d8b01f08c95c427a36c66aac769af4f Mon Sep 17 00:00:00 2001
From: Michal Suchanek <hramrach@gmail.com>
Date: Thu, 5 May 2016 17:31:54 -0700
Subject: [PATCH 08/10] mtd: spi-nor: simplify write loop

The spi-nor write loop assumes that what is passed to the hardware
driver write() is what gets written.

When write() writes less than page size at once data is dropped on the
floor. Check the amount of data writen and exit if it does not match
requested amount.

Signed-off-by: Michal Suchanek <hramrach@gmail.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Tested-by Cyrille Pitchen <cyrille.pitchen@atmel.com>
Acked-by: Michal Suchanek <hramrach@gmail.com>
Tested-by: Michal Suchanek <hramrach@gmail.com>
---
 drivers/mtd/spi-nor/spi-nor.c | 58 +++++++++++++++++++------------------------
 1 file changed, 25 insertions(+), 33 deletions(-)

--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -988,8 +988,8 @@ static int spi_nor_write(struct mtd_info
 	size_t *retlen, const u_char *buf)
 {
 	struct spi_nor *nor = mtd_to_spi_nor(mtd);
-	u32 page_offset, page_size, i;
-	int ret;
+	size_t page_offset, page_remain, i;
+	ssize_t ret;
 
 	dev_dbg(nor->dev, "to 0x%08x, len %zd\n", (u32)to, len);
 
@@ -997,45 +997,37 @@ static int spi_nor_write(struct mtd_info
 	if (ret)
 		return ret;
 
-	write_enable(nor);
+	for (i = 0; i < len; ) {
+		ssize_t written;
 
-	page_offset = to & (nor->page_size - 1);
-
-	/* do all the bytes fit onto one page? */
-	if (page_offset + len <= nor->page_size) {
-		ret = nor->write(nor, to, len, buf);
-		if (ret < 0)
-			goto write_err;
-		*retlen += ret;
-	} else {
+		page_offset = (to + i) & (nor->page_size - 1);
+		WARN_ONCE(page_offset,
+			  "Writing at offset %zu into a NOR page. Writing partial pages may decrease reliability and increase wear of NOR flash.",
+			  page_offset);
 		/* the size of data remaining on the first page */
-		page_size = nor->page_size - page_offset;
-		ret = nor->write(nor, to, page_size, buf);
+		page_remain = min_t(size_t,
+				    nor->page_size - page_offset, len - i);
+
+		write_enable(nor);
+		ret = nor->write(nor, to + i, page_remain, buf + i);
 		if (ret < 0)
 			goto write_err;
-		*retlen += ret;
+		written = ret;
 
-		/* write everything in nor->page_size chunks */
-		for (i = ret; i < len; ) {
-			page_size = len - i;
-			if (page_size > nor->page_size)
-				page_size = nor->page_size;
-
-			ret = spi_nor_wait_till_ready(nor);
-			if (ret)
-				goto write_err;
-
-			write_enable(nor);
-
-			ret = nor->write(nor, to + i, page_size, buf + i);
-			if (ret < 0)
-				goto write_err;
-			*retlen += ret;
-			i += ret;
+		ret = spi_nor_wait_till_ready(nor);
+		if (ret)
+			goto write_err;
+		*retlen += written;
+		i += written;
+		if (written != page_remain) {
+			dev_err(nor->dev,
+				"While writing %zu bytes written %zd bytes\n",
+				page_remain, written);
+			ret = -EIO;
+			goto write_err;
 		}
 	}
 
-	ret = spi_nor_wait_till_ready(nor);
 write_err:
 	spi_nor_unlock_and_unprep(nor, SPI_NOR_OPS_WRITE);
 	return ret;