Re: [microblaze-uclinux] Need some pool memory

[John Williams <jwilliams@xxxxxxxxxxxxxx>]

Hi George,

George Smith wrote:

>  I need some "pool" memory - memory that linux won't touch and I can use
> external dma into it. So I tried the: 
>  PARAMETER MAIN_MEMORY_SIZE = 0x01f00000
>  in my system.mss. 
> 
> That sets auto-config.in:
> # MAIN_MEMORY Settings
> define_hex CONFIG_XILINX_ERAM_START 0x80000000
> define_hex CONFIG_XILINX_ERAM_SIZE 0x01f00000

How much memory does the kernel report in the boot log?

> Which seems to me that linux would not touch about 
> 0x81efffff (or mod 4 of that).
> But when uclinux comes up I find memory from there up to the 32MB
> boundry has been painted with zeros. 

Hmm..  I wonder if it's not a power-of-two issue in the initial boot mem
allocator.

> So the question is how to get pool memory. Have I done something
> incorrect? Should I place it at the bottom of memory, which was the
> standard back in the old unix days??

You could try the MSS parameter MAIN_MEMORY_OFFSET that is supported in
recent versions of the uClinux BSP packages

MAIN_MEMORY_OFFSET = 0x100000
MAIN_MEMORY_SIZE = 0x1F00000

see if that works any better.

John
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