Trying to install OpenBSD, I get u-Boot error

[AndroTester]

Hi there.

I tried to install OpenBSD, I copied the minirootfs to sd card from an OpenBSD machine and copied relevant dtb to sd card:

dd if=miniroot64.fs of/dev/rsd0c bs=1m
mount /dev/sd0i /mnt
mkdir /mnt/allwinner
cp /usr/local/share/dtb/arm64/allwinner/sun50i-a64-pine64.dtb /mnt/allwinner


But it didn't help. I get 
U-Boot SPL 2018.09 (Oct 12 2018 - 03:54:15 -0600)
DRAM: 0 MiB
### ERROR ### Please RESET the board ###

Please advise