[PATCH v3 0/2] fastboot: mmc: fix bootloader offset

Heiko Schocher
2026-02-17T10:36:26Z

Not for all SoCs the bootloader start at offset 0x0,
in a hardware partition of an emmc. So we need the possibility to
set the correct offset, where bootloader starts.

Example:

imx8qxp revision C0 emmc Partition layout

| eMMC block / partition | Offset | Size | Purpose |
| ---------------------- | ---------- | ----- | ------------------------------ |
| /dev/mmcblk0boot0 | 0x0 | 2MB | imx-boot-container A |
| | 0x00220000 | 128kB | secure boot signature rootfs A |
| /dev/mmcblk0boot1 | 0x0 | 2MB | imx-boot-container B |
| | 0x00200000 | 8kB | U-Boot env 0 |
| | 0x00202000 | 8kB | U-Boot env 1 |
| | 0x00220000 | 128kB | secure boot signature rootfs B |

imx8qxp rev B0 emmc Partition layout

| eMMC block / partition | Offset | Size | Purpose |
| ---------------------- | ---------- | ----- | ------------------------------ |
| /dev/mmcblk0boot0 | 0x00008000 | 2MB | imx-boot-container A |
| | 0x00220000 | 128kB | secure boot signature rootfs A |
| /dev/mmcblk0boot1 | 0x0 | 8kB | U-Boot env 0 |
| | 0x00002000 | 8kB | U-Boot env 1 |
| | 0x00008000 | 2MB | imx-boot-container B |

If we flash now the bootloader image flash.bin on a B0 revision with

uuu FB: flash bootloader flash.bin

we overwrite the environment and board does not boot at all, as offset
is wrong.

To prevent any API change in the above command we propose
the following implementation from this series:

We add a new weak function fb_mmc_get_boot_offset() in drivers/fastboot/fb_block.c
which returns 0 and call this function instead of passing 0 for
the offset where offset is used/passed.

In SoC specific code (currently for IMX8QXP only) we implement this function
that it returns on B0 SoCs the 32k offset and on other SoC revisions the
offset 0.

This is tested on B0 and C0 based boards from siemens.

This patch should have no effect for other SoCs.

Changes in v3:
reworked the logic as Peng suggested, so newer SoC
revisions will also start from offset 0x0

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
- added Reviewed-by from Mattijs

Adrian Freihofer (2):
fastboot: mmc: make boot partition offset configurable
arch: imx8qxp: Override weak fb_mmc_get_boot_offset function

arch/arm/mach-imx/imx8/cpu.c | 21 +++++++++++++++++++++
drivers/fastboot/fb_block.c | 15 +++++++++++----
2 files changed, 32 insertions(+), 4 deletions(-)

--
2.20.1

base-commit: b99da05e1538b8fa153322da82917af2aa27e1d6