Multi-core supports fully operational on LS1028A.
In order to specify the number of core to use, you could use bootargs "maxcpus“, modify Linux Kernel configuration CONFIG_NR_CPUS or modify the dts file only defining CPU.
For example, you could specify "maxcpus=1" in the bootargs to only run Linux on core0.
Kernel command line: root=/dev/ram rw console=ttyS0,115200 maxcpus=1
Initializing one or the two CPU cores, you could refer to the following.
smp_setup_processor_id in arch/arm64/kernel/setup.c
__cpu_up in arch/arm64/kernel/smp.c
smp_init in kernel/smp.c