[coreboot] armv8 mmu limitation?

Folks,
We are working with a device that has 8GB DDR.

Using the basic mmu_config_range() call, twice, like this:

mmu_config_range((void *)0x080000000, DRAMSIZE, UNCACHED_MEM);
    mmu_config_range((void *)0x180000000, DRAMSIZE, UNCACHED_MEM);

print messages from Coreboot suggest the mmu calls are happy:

Mapping address range [0000000080000000:0000000180000000) as 
non-cacheable | read-write | non-secure | normal
Mapping address range [0000000180000000:0000000280000000) as 
non-cacheable | read-write | non-secure | normal

The debugger is not convinced and believes only 6GB got mapped.

I'm guessing tables are overflowing and perhaps granule or page sizes 
need to be changed or?
As mmu_init() takes no parameters, what mmu options are easily 
configurable within Coreboot?
Any pointers to correct code to look at is appreciated.

Cheers,
T.mike