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Subject: Re: how to support more than 512MB RAM for MIPS32 ?
From:   "Figo.zhang" <figo1802@gmail.com>
To:     Kevin Hickey <khickey@netlogicmicro.com>
Cc:     ralf@linux-mips.org, linux-mips@linux-mips.org
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Date:   Wed, 25 Nov 2009 23:31:14 +0800
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On Wed, 2009-11-25 at 08:37 -0600, Kevin Hickey wrote:
> We use HIGHMEM on the Au1300 to access any memory spaces >256 MB.  Our
> I/O area starts at 256 MB.  We just map the extra DRAM to any area
> outside the I/O space,

how to do map extra RAM to any ouside I/O space?
it is just motify:

1. arch/mips/kernel/setup.c: bootm_init()function, motity the define
"HIGHMEM_START", for me: 
#define HIGHMEM_START 0x2000,0000   //512MB

2. use add_memory_region, for me:
 add_memory_region(0x20000000, 0x40000000, BOOT_MEM_RAM); //extra 1G RAM

is it ok ?

Best,
Figo.zhang


>  enable highmem, and register it as BOOT_MEM_RAM
> with add_memory_region.  Works great.
> 
> =Kevin
> --
> Kevin Hickey
> Netlogic Microsystems
> 
> 
> On Wed, 2009-11-25 at 14:34 +0800, figo zhang wrote:
> > hi all,
> > 
> > I am using 24KEC SOC, i want to support larger more than 512MB RAM.
> > The mips32 architure  in Kseg0/Kseg1,
> > such as:
> > 0x8000,0000 ~ 0x92c0,0000  # 300MB for RAM
> > 0x92c0,0000 ~ 0xa000,0000  # 212 for I/O register
> > 
> > so, mips32 only support 300MB memory, i dont how to support more than
> > 512MB in linux-mips kernel , such as 2GB memory? it is using HIGHMEM
> > strategy
> > for kernel(ZONE_HIGHMEM)?
> > 
> > Best,
> > Figo.zhang
>