On the defective unit, the MMC continuously responds to CMD1 (SEND_OP_COND) with the busy flag -- ie: never finishing internal initialization.
Boot logs between units shows no discernible difference (debugging enabled).
Changing kernel/bootloader/rom shows no difference. MMC never finishes internal initialization.
1. Is there a way to manually interface with the MMC and send it commands from user mode, outside of the kernel?
2. What might cause the internal MMC to never finish its internal initialization?
3. What possible causing files/registers survive a kernel/bootloader/rom change, and can they be read/modified from user mode?
Any input is appreciated.
PS: Do not suggest re-partitioning, factory reset, or microwave .