[PATCH] cmd: sf: Support unaligned flash updates with 'sf update'

[Frieder Schrempf <frieder@fris.de>]

From: Frieder Schrempf <frieder.schrempf@kontron.de>

Currently 'sf update' supports only offsets that are aligned to the
erase block size of the serial flash. Unaligned offsets result in
something like:

=> sf update ${kernel_addr_r} 0x400 ${filesize}
device 0 offset 0x400, size 0x11f758
SPI flash failed in erase step

In order to support unaligned updates, we simply read the first full
block and check only the requested part of the block for changes. If
necessary, the block is erased, the first (unchanged) part of the block
is written back together with the second part of the block (updated data).

Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
---
 cmd/sf.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/cmd/sf.c b/cmd/sf.c
index eac27ed2d7..c54b4b10bb 100644
--- a/cmd/sf.c
+++ b/cmd/sf.c
@@ -171,30 +171,32 @@ static int do_spi_flash_probe(int argc, char *const argv[])
 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)
 {
+	u32 offset_aligned = ALIGN_DOWN(offset, flash->sector_size);
+	u32 sector_offset = offset - offset_aligned;
 	char *ptr = (char *)buf;
 
 	debug("offset=%#x, sector_size=%#x, len=%#zx\n",
 	      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, offset_aligned, flash->sector_size, cmp_buf))
 		return "read";
 	/* Compare only what is meaningful (len) */
-	if (memcmp(cmp_buf, buf, len) == 0) {
+	if (memcmp(cmp_buf + sector_offset, buf, len) == 0) {
 		debug("Skip region %x size %zx: no change\n",
 		      offset, len);
 		*skipped += len;
 		return NULL;
 	}
 	/* Erase the entire sector */
-	if (spi_flash_erase(flash, offset, flash->sector_size))
+	if (spi_flash_erase(flash, offset_aligned, flash->sector_size))
 		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 + sector_offset, buf, len);
 		ptr = cmp_buf;
 	}
 	/* Write one complete sector */
-	if (spi_flash_write(flash, offset, flash->sector_size, ptr))
+	if (spi_flash_write(flash, offset_aligned, flash->sector_size, ptr))
 		return "write";
 
 	return NULL;
@@ -230,7 +232,10 @@ static int spi_flash_update(struct spi_flash *flash, u32 offset,
 		ulong last_update = get_timer(0);
 
 		for (; buf < end && !err_oper; buf += todo, offset += todo) {
-			todo = min_t(size_t, end - buf, flash->sector_size);
+			if (offset % flash->sector_size)
+				todo = flash->sector_size - (offset % flash->sector_size);
+			else
+				todo = min_t(size_t, end - buf, flash->sector_size);
 			if (get_timer(last_update) > 100) {
 				printf("   \rUpdating, %zu%% %lu B/s",
 				       100 - (end - buf) / scale,
-- 
2.33.0