Non-contiguous physical memory

[Kumar Gala]

On Jan 21, 2009, at 9:18 AM, Aaron Pace wrote:

> Hello,
>
> I'm working on a design using a Freescale MPC8572 processor.
> We are using 4 gigs of memory, and also need a window of 512 megs for
> PCI-E devices.
> What I have done is set up the first 2G of memory from 0x0 - 0x7f, the
> PCI windows from 0x8 - 0x9f, localbus devices + CCSRBAR from 0xf -
> 0xffffffff, and the second 2G of ram from 0x1.0000.0000 -
> 0x1.8000.0000.
> I've got this set up in U-boot (although it only uses the low mem),
> but Linux will only use the first contiguous physical area (the
> message is "Only using first contiguous memory region").
> Is it possible to have multiple non-contiguous physical memory chunks
> used for memory allocation?
> If not, is there a better way to set this up without losing large
> chunks of memory?

Its possible in that Linux supports this.  However the PPC32 code does  
not exist and would need to be added to support non-contiguous memory  
ranges.

What exact PCI-E needs do you have?  Is PCI-E performance critical?   
Is (are) your pci device(s) 64-bit address capable?

I ask because depending on the answers doing straight 4G and PCI above  
that range might be sufficient for your needs.

- k