Max RAM for Linux only 1GB?

Max RAM for Linux only 1GB?

[Prakash Kanthi]

Folks,

I have over 1GB DIMM RAM on my board running PPC 405.
How can i ioremap that to my OS? As Linux virtual
space starts at 0xC0000000, we have only 1GB more for
all virtual space mappings.

Even if i move 0xC0000000 to 0x80000000, what will
happen to TLB settings? Any problem there to map 1GB
additional RAM?

Any idea as to how i can do this?

Thanks,
Prakash


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Re: Max RAM for Linux only 1GB?

[John Whitney]

Prakash,

The easiest route it to turn on highmem support (CONFIG_HIGHMEM).  As far as
I know, this does work for the PowerPC.  My understanding is that the kernel
doesn't directly use this memory, but will allow user-space programs to use
it (mapped into their memory space), which should in turn free up the memory
the kernel DOES use.

I think you'll need to start playing with the kernel start address if you
want the kernel to benefit directly from the additional memory.  I know this
has been done successfully to 0xA0000000, not sure about all the way down to
0x80000000 (but I can't think of why it wouldn't off the top of my head).

John

On 10/31/03 11:58 AM, "Prakash Kanthi" <pkanthi@yahoo.com> wrote:

>
> Folks,
>
> I have over 1GB DIMM RAM on my board running PPC 405.
> How can i ioremap that to my OS? As Linux virtual
> space starts at 0xC0000000, we have only 1GB more for
> all virtual space mappings.
>
> Even if i move 0xC0000000 to 0x80000000, what will
> happen to TLB settings? Any problem there to map 1GB
> additional RAM?
>
> Any idea as to how i can do this?
>
> Thanks,
> Prakash
>
>
>
>


** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/

Re: Max RAM for Linux only 1GB?

[Matt Porter]

On Fri, Oct 31, 2003 at 08:58:21AM -0800, Prakash Kanthi wrote:
>
> Folks,
>
> I have over 1GB DIMM RAM on my board running PPC 405.
> How can i ioremap that to my OS? As Linux virtual
> space starts at 0xC0000000, we have only 1GB more for
> all virtual space mappings.
>
> Even if i move 0xC0000000 to 0x80000000, what will
> happen to TLB settings? Any problem there to map 1GB
> additional RAM?
>
> Any idea as to how i can do this?

Use CONFIG_HIGHMEM or move KERNELBASE like you suggest.

You don't ioremap your system memory (well, under normal
conditions).

-Matt

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