The mdadm assumes the Video ROM is present in the system (0xc0000 ~ 0xc7fff), so the it scans the other option ROMs (including Intel RST option ROM) starting from address 0xc8000 to 0xfffff.
If Video ROM is absent, the other option ROMs will start from 0xc0000. In my case, the Intel RST option ROM is located at Video ROM area, and mdadm is not finding it. The find_imsm_hba_orom() returns NULL.
Due to the changes introduced in mdadm 3.3.4 (commits 7eee461 “Assemble: don’t assemble IMSM array without OROM.” and 8360760 “Assemble: really don’t assemble IMSM array without OROM.”) the mdadm is reporting the Intel RAID is not supported on my platform.
Regards,
Tomasz