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STM32MP257F-AI3 Custom Board Not Booting from eMMC (A35 Master) After SD Image Flash

_Krishna
Associate II

‎2025-11-09 3:16 AM

We are working on a custom board based on STM32MP257F-AI3. We flashed an X-Linux RT patched image via SD card in boot mode 0001(A35-Master), and in the ST Cube Programmer flashing completed successfully with a "download successful" pop-up in when boot mode USB/UART switches configuration is 0000.

After powering off, we set the boot switches to 0010 (eMMC boot, A35 master), but the board fails to boot properly from eMMC.

Could you please help us identify:

  1. Whether the image correctly written to the eMMC boot partitions (FSBL, SSBL, U-Boot, etc.)?

  2. Any mandatory post-flash steps required for enabling eMMC boot on STM32MP257?

  3. The correct boot configuration (TF-A, OP-TEE, U-Boot, extlinux or boot partition flags)

Any guidance on debugging or verifying the eMMC boot flow would be helpful.

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erna23
Associate II

‎2025-11-09 5:20 AM

To boot STM32MP257 from eMMC:

  1. Ensure the full image (FSBL, SSBL, TF-A, U-Boot, OP-TEE, rootfs) is flashed to eMMC.

  2. Set boot switches = 0010 (A35 master).

  3. Verify eMMC partitions and boot flags (extlinux/bootable).

  4. Use UART console to debug early boot messages.

Common issues: missing FSBL/SSBL, wrong partition flags, or extlinux misconfiguration.

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