Re: [coreboot] How to test RAM beyond 640 kByte boundary

[Marc Jones]

llandre wrote:
> > > > Why is the RAM physically unaccessible beyond 640 KByte at this stage?
> > >
> > > Which chipset / board? It's not necessarily unaccessible.
> >
> > AMD Geode LX/CS5536
>
> I forgot to mention that is a custom board.

The 640-1MB area is covered by a basemask descriptor (A0000-BFFFFh) 
setup and used by graphics and a swisscheese descriptor (C0000h-FFFFFh) 
for the legacy shadow memory hole. In 
northbridge/amd/lx/northbridgeinit.c see the gliutables structures.

In both tables you could change the swisscheese to allow reads and 
writes to memory like this:

{.desc_name = MSR_GLIU0_SHADOW,.desc_type = SC_SHADOW,.hi = MSR_MC + 
0xFFFF,.lo = 0xFFFF0003},

Marc