Cannot activate multiple CPUs.

[chris warth]

Is there a trick to bringing up multiple CPUs on an SOC?
My kernel is not bringing up secondary CPUs.

Running a kernel compiled from v4.10 sources on an LS1046A reference board.
Support for this platform only arrived in the mainline sources in
v4.10, so it is pretty new, and
there are clearly differences from the vendor supplied SDK sources.

Configured with generic arm64 defconfig.
Loading the kernel via `booti` in u-boot.  Provided
fsl-ls1046a-rdb.dtb as the device tree.
Console log indicates only a single CPU is available.

[    0.083735] EFI services will not be available.
[    0.096301] smp: Bringing up secondary CPUs ...
[    1.141306] CPU1: failed to come online
[    1.145159] CPU1: failed in unknown state : 0x0
[    2.202164] CPU2: failed to come online
[    2.206016] CPU2: failed in unknown state : 0x0
[    3.263021] CPU3: failed to come online
[    3.266873] CPU3: failed in unknown state : 0x0
[    3.271449] smp: Brought up 1 node, 1 CPU

Is it possible that multiple cores are not supported in the mainline code?
Or am I missing some piece of configuration that would bring up multiple cores?

Thanks in advance,

- Chris