We made a custom board based on the IMX28EVK, but using the i.MX280, with DDR2 and boot from SSP0 (microSD card).
In our initial tests we found out that some SD cards couldn't boot on our board, but were successful on the EVK.
So I started looking for differences and ended up comparing the OTP flags. The EVK has only one OTP flag set, enabling 12mA drive on SSP0 pins. After burning that fuse, our board was able to boot with the problematic cards.
The boot message when the SD card fails, is just: 0x8020a014
The same card started working after we burned ENABLE_SSP_12MA_DRIVE bit in HW_OCOTP_ROM7 register of the same board.
Another board with OTP unchanged fails to boot the same card.
Now the question is: why is that flag necessary? is it a workaround for design issues of the EVK (and so in our board too) or is it required for proper boot with SD cards?
Can anyone shed a light on this matter?