Direct Kernel Boot on STM32MP1

[HZ890]

Hi everyone,

I'm attempting to optimize the boot process on my STM32MP157F-DK2 board by removing U-Boot and booting the Linux kernel directly via the FIP. I've followed the documented steps for STM32MP1:

1. TF-A BL2 Modifications:

   • Updated STM32MP_BL33_BASE and STM32MP_BL33_MAX_SIZE in the STM32MP1 header file.

   • Increased the SDMMC timeout in stm32_sdmmc2.c to accommodate the larger kernel image.

2. FIP Creation:

   • Recompiled TF-A with my modifications.

   • Created a new FIP where I replaced the U-Boot binary and its DTB with my Linux kernel Image and DTB.

   • The new FIP (fip.bin) now contains the kernel and DTB.

3. Flash Layout TSV Modifications:
   I updated the TSV file to allocate a larger space for the FIP. Below is the relevant excerpt:

   

Despite these modifications, every time I execute the process, it fails. My questions are:

• What is the purpose of the bootfs partition?
  Since my new FIP (fip.bin) already contains the Linux kernel and its DTB, I'm unclear why the flash layout still reserves a bootfs partition. Is it meant for additional boot configurations, an initial ramdisk, or something else?

• Why is the u-boot-env partition still present?
  If U-Boot is being removed entirely from the boot chain, what role does the U-Boot environment play here? Is it kept for legacy or recovery purposes?

I would really appreciate any insights or suggestions on what might be going wrong or what additional changes I need to consider for a successful direct kernel boot setup on STM32MP157f-dk2.

Thanks in advance for your help!

[Erwan SZYMANSKI]

Hello @HZ890 ,
Can you please precise a bit the status when you says "everytime I execute the process it fails" ? Do you talk at boot time or during the preparation process ? 

Do you have some error logs or anything to share ? 

Kind regards,
Erwan.

[HZ890]

Dear Erwan SZYMANSKI,

I received the following error during the boot time process:

NOTICE: CPU: STM32MP157FAC Rev.Z NOTICE: Model: STMicroelectronics STM32MP157F-DK2 Discovery Board NOTICE: Board: MB1272 Var4.0 Rev.C-03 NOTICE: BL2: v2.10-stm32mp1-r1.0(release):() NOTICE: BL2: Built : 11:26:24, Apr 7 2025 ERROR: BL2: Failed to load image id 1 (-27)

If you have any pointers or an example with those platforms, it would be much appreciated.

Best Regards,
Hassan