Early boot debug on STM32MP1, SD-Card boot not working
I'm working on a project using the Seeed Studio STM32MP157C-Odyssey-SoM (it is a module with the STM32MP1, DDR, eMMC and STPMIC). I am making a new PCB into which the module is plugged.
When using the module on the original host board from Seeed, both the eMMC (SDMMC2 controller) and the SD-Card (SDMMC1 controller) boot work.
On my board only the eMMC boot works. When using the SWD debugger, I found that the CPU does not even enter the FSBL, but remains stuck in the boot ROM. By checking the SD-Card connection, I found that the CPU does not even attempt a write (and the SDMMC1 controller has only the reset values in its registers).
I also determined that the boot mode is properly detected in the SYSCFG_BOOTR register.
Is there a way to debug the boot ROM?
I understand the code is not available, but I hope to be able to determine what is happening by reading peripheral registers, which ones should I check?
Thanks for your help