Re: Non-contiguous physical memory

[Michele Pallaro <michele.pallaro@alcatel-lucent.it>]

Hello,
	I have a similar problem with my custom board CPU mpc8548 (E500V2) with
4Gbytes of RAM

	  0x0000_0000 --    0x7FFF_FFFF  2Gbytes
	0x1_0000_0000 -- 0x1_7FFF_FFFF   2Gbytes

I Enable the option PHYS_64BIT, and set in dts

memory {
                #address-cells = <2>;
                #size-cells = <1>;   
                device_type = "memory";
                reg = <00000000 00000000 00000000 7FFFFFFF
                       00000001 00000000 00000000 7FFFFFFF>;
        };  

But the kernel can see just 2Gbytes of memory.
How the kernel can see the other 2Gbytes ?

	Michele
	

On Wed, 2009-01-21 at 11:28 -0600, Kumar Gala wrote:
> 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
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