SMP8634 DRAM memory issue

SMP8634 DRAM memory issue

[linux-mips]

Hi,

We've got an SMP8634 based set-top box from a 3rd party and are trying to
port some middleware to it.
Everything seems to work out fine, except for one thing ... the amount of
memory for kernel space.

The box physically has two 64MB chips and two 32MB chips.  
The kernel is only seeing the two 32MB chips, apparently attached to DRAM0.

The problem is the following:

1) The middleware requires more memory in kernel space to allocalte big
graphical surfaces.
2) Whatever runs before the kernel is also from a 3rd party and we don't
have access to it.
3) We can't change anything on the box hardware.

This means, we would only be able to patch starting from the Linux kernel.

Do you see any way to swap what the kernel sees to be 128MB instead of 64MB
and the user space 64MB minus whatever is allocated for the initial RAM
disc?
The 64MB for user space are sufficient, we just need more then 64 MB on
kernel space.

Regards,

Robert

-- 
Robert Berger
Embedded Software Specialist

Reliable Embedded Systems
Consulting Training Engineering
Tel.: (+30) 697 593 3428
Fax.:(+30 210) 684 7881
URL: http://www.reliableembeddedsystems.com
--
...This above all: to thine own self be true.-- Shakespeare

Re: SMP8634 DRAM memory issue

[David Daney]

linux-mips@reliableembeddedsystems.com wrote:
> Hi,
> 
> We've got an SMP8634 based set-top box from a 3rd party and are trying to
> port some middleware to it.
> Everything seems to work out fine, except for one thing ... the amount of
> memory for kernel space.
> 
> The box physically has two 64MB chips and two 32MB chips.  
> The kernel is only seeing the two 32MB chips, apparently attached to DRAM0.
> 
> The problem is the following:
> 
> 1) The middleware requires more memory in kernel space to allocalte big
> graphical surfaces.
> 2) Whatever runs before the kernel is also from a 3rd party and we don't
> have access to it.
> 3) We can't change anything on the box hardware.
> 
> This means, we would only be able to patch starting from the Linux kernel.
> 
> Do you see any way to swap what the kernel sees to be 128MB instead of 64MB
> and the user space 64MB minus whatever is allocated for the initial RAM
> disc?
> The 64MB for user space are sufficient, we just need more then 64 MB on
> kernel space.
> 

It depends if the 128MB is on DRAM0 or DRAM1.  Typically DRAM1 is not
usable by the kernel, although others have tried to access it as high-mem.

If DRAM0 is 128MB, *and* you have access to the kernel command line, you
 might try to append something like 'mem=96M'.  You may need to leave
some space in DRAM0 for the media components.  If not try jacking it up
to mem=128M.  Said media components do need memory too, so it may not be
possible to get more for the kernel and have it all work together.

David Daney