cmd_sf: let "sf update" preserve the final part of the last sector

Since "sf update" erases the last block as a whole, but only rewrites
the meaningful initial part of it, the rest would be left erased,
potentially erasing meaningful information.
So, as a safety measure, have it rewrite the original content.

Signed-off-by: Gerlando Falauto <gerlando.falauto@keymile.com>
Cc: Valentin Longchamp <valentin.longchamp@keymile.com>
Cc: Holger Brunck <holger.brunck@keymile.com>
Acked-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Jagannadha Sutradharudu Teki <jaganna@xilinx.com>

diff --git a/common/cmd_sf.c b/common/cmd_sf.c
index 4af0f0af26bcfa3afbc63708fb019a89cc99d274..3f60979ae78fa9e33d331940db01d6eb25528626 100644 (file)
--- a/common/cmd_sf.c
+++ b/common/cmd_sf.c
@@ -152,8 +152,10 @@ static const char *spi_flash_update_block(struct spi_flash *flash, u32 offset,
 {
        debug("offset=%#x, sector_size=%#x, len=%#zx\n",
              offset, flash->sector_size, len);
-       if (spi_flash_read(flash, offset, len, cmp_buf))
+       /* Read the entire sector so to allow for rewriting */
+       if (spi_flash_read(flash, 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);
@@ -163,8 +165,17 @@ static const char *spi_flash_update_block(struct spi_flash *flash, u32 offset,
        /* Erase the entire sector */
        if (spi_flash_erase(flash, offset, flash->sector_size))
                return "erase";
+       /* Write the initial part of the block from the source */
        if (spi_flash_write(flash, offset, len, buf))
                return "write";
+       /* If it's a partial sector, rewrite the existing part */
+       if (len != flash->sector_size) {
+               /* Rewrite the original data to the end of the sector */
+               if (spi_flash_write(flash, offset + len,
+                                   flash->sector_size - len, &cmp_buf[len]))
+                       return "write";
+       }
+
        return NULL;
 }