[PATCH v3 1/2] fastboot: mmc: make boot partition offset configurable

[Heiko Schocher <hs@nabladev.com>]

From: Adrian Freihofer <adrian.freihofer@siemens.com>

i.MX8QXP rev C.0 requires boot container stored at offset 0KB
for eMMC, while i.MX8QXP pre C.0 requires boot container stored
at offset 32KB for eMMC.

To use one U-Boot binary to support different chip revisions,
introduce fb_mmc_get_boot_offset() to allow override the default
offset when writing to eMMC boot partitions.

This enables support for devices with non-standard boot partition
layouts, such as those requiring an offset for correct bootloader
placement.

Signed-off-by: Adrian Freihofer <adrian.freihofer@siemens.com>
Signed-off-by: Heiko Schocher <hs@nabladev.com>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@kernel.org>
---

(no changes since v2)

Changes in v2:
- added Reviewed-by from Mattijs
- Used the commit message as Peng suggested (with a small
  checkpatch fix:
  WARNING: 'writting' may be misspelled - perhaps 'writing'?
- rebased to mainline
  b99da05e153 - (tag: v2026.04-rc2, origin/master, origin/HEAD) Prepare v2026.04-rc2

 drivers/fastboot/fb_block.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/fastboot/fb_block.c b/drivers/fastboot/fb_block.c
index 2a7e47992f8..51d1abb18c7 100644
--- a/drivers/fastboot/fb_block.c
+++ b/drivers/fastboot/fb_block.c
@@ -28,6 +28,11 @@
  */
 #define FASTBOOT_MAX_BLOCKS_WRITE 65536
 
+__weak lbaint_t fb_mmc_get_boot_offset(void)
+{
+	return 0;
+}
+
 struct fb_block_sparse {
 	struct blk_desc	*dev_desc;
 };
@@ -160,7 +165,8 @@ void fastboot_block_raw_erase_disk(struct blk_desc *dev_desc, const char *disk_n
 
 	debug("Start Erasing %s...\n", disk_name);
 
-	written = fb_block_write(dev_desc, 0, dev_desc->lba, NULL);
+	written = fb_block_write(dev_desc, fb_mmc_get_boot_offset(),
+				 dev_desc->lba, NULL);
 	if (written != dev_desc->lba) {
 		pr_err("Failed to erase %s\n", disk_name);
 		fastboot_response("FAIL", response, "Failed to erase %s", disk_name);
@@ -211,7 +217,8 @@ void fastboot_block_erase(const char *part_name, char *response)
 	if (fastboot_block_get_part_info(part_name, &dev_desc, &part_info, response) < 0)
 		return;
 
-	fastboot_block_raw_erase(dev_desc, &part_info, part_name, 0, response);
+	fastboot_block_raw_erase(dev_desc, &part_info, part_name,
+				 fb_mmc_get_boot_offset(), response);
 }
 
 void fastboot_block_write_raw_disk(struct blk_desc *dev_desc, const char *disk_name,
@@ -224,7 +231,7 @@ void fastboot_block_write_raw_disk(struct blk_desc *dev_desc, const char *disk_n
 	blkcnt = ((download_bytes + (dev_desc->blksz - 1)) & ~(dev_desc->blksz - 1));
 	blkcnt = lldiv(blkcnt, dev_desc->blksz);
 
-	if (blkcnt > dev_desc->lba) {
+	if ((blkcnt + fb_mmc_get_boot_offset()) > dev_desc->lba) {
 		pr_err("too large for disk: '%s'\n", disk_name);
 		fastboot_fail("too large for disk", response);
 		return;
@@ -232,7 +239,7 @@ void fastboot_block_write_raw_disk(struct blk_desc *dev_desc, const char *disk_n
 
 	printf("Flashing Raw Image\n");
 
-	blks = fb_block_write(dev_desc, 0, blkcnt, buffer);
+	blks = fb_block_write(dev_desc, fb_mmc_get_boot_offset(), blkcnt, buffer);
 
 	if (blks != blkcnt) {
 		pr_err("failed writing to %s\n", disk_name);
-- 
2.20.1