RE: Lots of memory on 826x

What about moving the VMALLOC_START and VMALLOC_END #defines to
something else (like start at 0x80000000 and end at 0xc0000000), or will
that break some assumptions in the kernel about the position of the
vmalloc area?

-----Original Message-----
From: Matt Porter [mailto:mporter@kernel.crashing.org]=20
Sent: Tuesday, March 08, 2005 14:33
To: Rune Torgersen
Cc: Kumar Gala; linuxppc-embedded@ozlabs.org
Subject: Re: Lots of memory on 826x
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On Tue, Mar 08, 2005 at 12:37:33PM -0600, Rune Torgersen wrote:

quoted

Ok... Got a little closer....
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I have PCI (outbound) mapped in the area 0x80000000-0x8fffffff
(prefetch/non-prefetch and IO)
IMMR of cource is at 0xf0000000
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So I map the IO as following:
	/* Map IMMR region to a 256MB BAT */
	addr =3D (cpm2_immr !=3D NULL) ? (uint)cpm2_immr : CPM_MAP_ADDR;
	io_block_mapping(addr, addr, 0x10000000, _PAGE_IO);
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	io_block_mapping(0x80000000, 0x80000000, 0x10000000, _PAGE_IO);
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Now I can almost boot....:
It craches when trying to read from harddisk
(only happens with more than 512MB)

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That's expected if you are going to 768MB. You have kernel lowmem
being mapped at 0xc0000000+<size_of_system_memory>. With 768MB that
takes you all the way to where you have the IMMR mapped 1:1 I
guess. This leaves no room for vmalloc space.  With 768MB of ram
the kernel will calculate VMALLOC_START at 0xf1000000 which is a
problem.
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A few options are:
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* Move the IMMR much higher to allow vmalloc space
* Modify maximum low memory to limit to 512MB using the advanced
  options menu
* Modify KERNELBASE to something like 0xa0000000 using the advanced
  options menu
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All of these methods will provide addition vmalloc space.
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Don't forget to turn on HIGHMEM to use everything above MAX_LOW_MEM.
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-Matt
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