Hello Emmanuel,
booting current FreeBSD fails since patch f59f0825e8b9fdeb8abe43ffd10c5119ca1a032f efi_loader: parameter checks BLOCK_IO_PROTOCOL
The reason is that the buffer used by FreeBSD to read is not block aligned.
The UEFI spec requires that EFI_BLOCK_IO_PROTOCOL.ReadBlocks() returns EFI_INVALID_PARAMETER if the buffer is not properly aligned (i.e. is not a multiple of EFI_BLOCK_IO_MEDIA.IoAlign)
FreeBSD does not guarantee this alignment, e.g. efi_disk_read_blocks() is called with buffer 00000000995b08d0 which is not aligned to a multiple of 512.
FreeBSD function efipart_readwrite writes this error message: efipart_readwrite: rw=1, blk=62333952 size=1 status=2
The problem can be traced back to the FreeBSD line:
stand/efi/libefi/efipart.c(1043) efipart_realstrategy(): blkbuf = malloc(blkio->Media->BlockSize);
U-Boot does not yet implement the EFI_DISK_IO_PROTOCOL which is a wrapper for the EFI_BLOCK_IO_PROTOCOL allowing unaligned access.
malloc() could be replaced in FreeBSD by AllocatePages() which returns a 4096 byte aligned memory block.
Best regards
Heinrich