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
=20
On Tue, Mar 08, 2005 at 12:37:33PM -0600, Rune Torgersen wrote:
quoted
Ok... Got a little closer....
=20
I have PCI (outbound) mapped in the area 0x80000000-0x8fffffff
(prefetch/non-prefetch and IO)
IMMR of cource is at 0xf0000000
=20
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);
=20
io_block_mapping(0x80000000, 0x80000000, 0x10000000, _PAGE_IO);
=20
Now I can almost boot....:
It craches when trying to read from harddisk
(only happens with more than 512MB)
=20
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.
=20
A few options are:
=20
* 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
=20
All of these methods will provide addition vmalloc space.
=20
Don't forget to turn on HIGHMEM to use everything above MAX_LOW_MEM.
=20
-Matt
=20
=20
Hmm, I think there is an expectation that virt->phys is a simple=20
translation (ie, subtract KERNELBASE) for lowmem. lowmem most parts=20
tops out at 768M. So changing VMALLOC_START would break that.
Is there an issue with moving the IMMR virt address up higher?
- kumar
On Mar 8, 2005, at 3:16 PM, Rune Torgersen wrote:
What about moving the VMALLOC_START and VMALLOC_END #defines to
something else (like start at 0x80000000 and end at 0xc0000000), or=20=
will
that break some assumptions in the kernel about the position of the
vmalloc area?
quoted
-----Original Message-----
> From: Matt Porter [mailto:mporter@kernel.crashing.org]
quoted
Sent: Tuesday, March 08, 2005 14:33
> To: Rune Torgersen
> Cc: Kumar Gala; linuxppc-embedded@ozlabs.org
quoted
Subject: Re: Lots of memory on 826x
>
quoted
On Tue, Mar 08, 2005 at 12:37:33PM -0600, Rune Torgersen wrote:
> > Ok... Got a little closer....
> >
quoted
quoted
I have PCI (outbound) mapped in the area 0x80000000-0x8fffffff
> > (prefetch/non-prefetch and IO)
> > IMMR of cource is at 0xf0000000
> >
quoted
quoted
So I map the IO as following:
> > =A0=A0=A0 /* Map IMMR region to a 256MB BAT */
> > =A0=A0=A0 addr =3D (cpm2_immr !=3D NULL) ? (uint)cpm2_immr : =
CPM_MAP_ADDR;
quoted
quoted
=A0=A0=A0 io_block_mapping(addr, addr, 0x10000000, _PAGE_IO);
> >
quoted
quoted
=A0=A0=A0 io_block_mapping(0x80000000, 0x80000000, 0x10000000, =
_PAGE_IO);
> >
quoted
quoted
Now I can almost boot....:
It craches when trying to read from harddisk
> > (only happens with more than 512MB)
>
quoted
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.=A0 With 768MB of ram
> the kernel will calculate VMALLOC_START at 0xf1000000 which is a
> problem.
>
quoted
A few options are:
>
quoted
* Move the IMMR much higher to allow vmalloc space
> * Modify maximum low memory to limit to 512MB using the advanced
>=A0=A0 options menu
> * Modify KERNELBASE to something like 0xa0000000 using the advanced
>=A0=A0 options menu
>
quoted
All of these methods will provide addition vmalloc space.
Don't forget to turn on HIGHMEM to use everything above MAX_LOW_MEM.
-Matt
>
quoted