Booting current FreeBSD fails since patch
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:
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.
I've opened this up: https://reviews.freebsd.org/D21655
Commit 16ef880ce6ee ("loader.efi: efipart needs to use ioalign") was merged into FreeBSD on Sep 17th, 2019.