I think that the correct steps after my unlucky MMC0 erase were:
Code:
- attach serial cable
- boot
- during boot enter recovery menu
- there select "I. Initialize Partition Table (fdisk) and format FAT"
- reboot
- immediately after restart enter any key to stop autoboot
- enter "bist" and then "fastboot"
- via fastboot tool flash diags and data partitions using backed-up data
- reboot
- immediately after restart enter any key to stop autoboot
- boot into diags (run bootargs_diags ; bootm 0xE41000)
- in system diags menu export USB storage (menu "U) USB device mode")
- mount USB storage, copy system partition backup file to it and correctly unmount
- quit USB storage mode (menu "Q ~ to continue")
- get login prompy (menu "D) Exit, Reboot or Disable Diags" and then "L) Exit to login prompt")
- login as root (default password can be calculated but you may as well update your backup to alter it prior fastboot flash)
- flash system partition (dd if=/mnt/base-us/mmcblk0p1.bin of=/dev/mmcblk0p1 bs=16384)
- reboot
I'll try to write some step in more detail on wiki, including "screenshots" of individual menus.