Is STM32MP13 custom board with eMMC but no JTAG, no SD, and no serial useless?

[cbcooper]

The STM32MP135AAE3 board was designed incorrectly, they have pins for a JTAG but forgot to actually route them to the MPU.  The eMMC is not going to have a first-stage bootloader on it, and it's looking like it's not possible to flash an SPL to the eMMC over USB alone?  Management won't be happy to do another board spin but it's sure looking like that's the only path forward.

[cbcooper]

ChatGPT says:

1. USB DFU alone cannot flash first-stage bootloader (SPL) to eMMC on a totally blank STM32MP135.

2. This is not a dfu-util bug — it’s how the STM32MP1 ROM works.

3. You need hardware access to write SPL + U-Boot to eMMC:

• Option A: SWD / JTAG (ST-LINK)

  • CubeProgrammer can directly write SPL + U-Boot to eMMC.

• Option B: SD card boot

  • The ROM can load a SPL + U-Boot image from SD into RAM and then copy it to eMMC.