[PATCH] cmd: sf: Handle unaligned 'update' start offset

[Marek Vasut]

Currently the 'sf update' command fails in case the 'start' offset is
not aligned to SPI NOR erase block size. Add the missing alignment
calculation. In case the start offset is in the middle of erase block,
round start address down to the nearest aligned one, compare only the
updated data between what is in the SPI NOR and what is being written,
copy new data at offset of the compare buffer, and write back the entire
erase block.

This is useful e.g. on i.MX6Q where the u-boot-with-spl.imx is at
offset 0x400 in the SPI NOR, while the SPI NOR may have erase block
size e.g. 0x1000 bytes.

Signed-off-by: Marek Vasut <marex at denx.de>
---
Cc: Bin Meng <bmeng.cn at gmail.com>
Cc: Jagan Teki <jagan at amarulasolutions.com>
Cc: Jan Kiszka <jan.kiszka at siemens.com>
Cc: Pratyush Yadav <p.yadav at ti.com>
Cc: Sean Anderson <seanga2 at gmail.com>
---
 cmd/sf.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/cmd/sf.c b/cmd/sf.c
index bd102f5af9d..f9b2d9a47a7 100644
--- a/cmd/sf.c
+++ b/cmd/sf.c
@@ -179,16 +179,18 @@ static const char *spi_flash_update_block(struct spi_flash *flash, u32 offset,
 		size_t len, const char *buf, char *cmp_buf, size_t *skipped)
 {
 	char *ptr = (char *)buf;
+	u32 start_offset = offset % flash->sector_size;
+	u32 read_offset = offset - start_offset;
 
-	debug("offset=%#x, sector_size=%#x, len=%#zx\n",
-	      offset, flash->sector_size, len);
+	debug("offset=%#x+%#x, sector_size=%#x, len=%#zx\n",
+	      read_offset, start_offset, flash->sector_size, len);
 	/* Read the entire sector so to allow for rewriting */
-	if (spi_flash_read(flash, offset, flash->sector_size, cmp_buf))
+	if (spi_flash_read(flash, read_offset, flash->sector_size, cmp_buf))
 		return "read";
 	/* Compare only what is meaningful (len) */
-	if (memcmp(cmp_buf, buf, len) == 0) {
-		debug("Skip region %x size %zx: no change\n",
-		      offset, len);
+	if (memcmp(cmp_buf + start_offset, buf, len) == 0) {
+		debug("Skip region %x+%x size %zx: no change\n",
+		      start_offset, read_offset, len);
 		*skipped += len;
 		return NULL;
 	}
@@ -197,7 +199,7 @@ static const char *spi_flash_update_block(struct spi_flash *flash, u32 offset,
 		return "erase";
 	/* If it's a partial sector, copy the data into the temp-buffer */
 	if (len != flash->sector_size) {
-		memcpy(cmp_buf, buf, len);
+		memcpy(cmp_buf + start_offset, buf, len);
 		ptr = cmp_buf;
 	}
 	/* Write one complete sector */
@@ -238,6 +240,8 @@ static int spi_flash_update(struct spi_flash *flash, u32 offset,
 
 		for (; buf < end && !err_oper; buf += todo, offset += todo) {
 			todo = min_t(size_t, end - buf, flash->sector_size);
+			todo = min_t(size_t, end - buf,
+				     flash->sector_size - (offset % flash->sector_size));
 			if (get_timer(last_update) > 100) {
 				printf("   \rUpdating, %zu%% %lu B/s",
 				       100 - (end - buf) / scale,
-- 
2.35.1