Re: [microblaze-uclinux] Question

[Aurelian Lazarut <aurelian.lazarut@xxxxxxxxxxx>]

Hi John,

On Wed, 2004-02-04 at 19:15, John McGrath wrote:
> Hi All,
> I am attempting to compile the uClinux distribution for the Xilinx AFX 
> 456fg board. It is a basic board with just 8mb of SDRAM, a serial 
> interface and 8 led's.
You have sufficient hardware there, you don't need to use flash to store
the kernel + root file system, it can be downloaded in RAM and executed
there (sram in your case)
> 
> I have a few questions:
> 
> a)As it has no flash, I would be interested in cutting down the kernel 
> to its bare bones - i.e. making it as compact as possible.
you need ~2M bytes for image.bin (uncompressed) why cutting the size?

> Does anyone know of certain features I can cut out to improve this? Do 
> the default settigns when I configure uClinux choose minimal options?
You will have an already "shrink" version if you run without net support
(you don't have the ethernet on AFX right?) 
> 
> b)What are the primary files I need to change to get my board supported 
> - I have seen the mbvanilla.ln linker script, and also the 
> asm/mbvanilla.h files in the distribution. If I change all the 
> base-addresses here, should this be enough?
Yes
> 
> What is the memory controller (defined in the mbvanilla.h) ? I do not 
> have one of these in my design. I simply have some SRAM directly onto 
> the OPB bus, which is at base address 0x81800000 - I dont think I need a 
> separate memory controller for this, so how do I set this parameter so 
> it will work - do I simply set it to the base address of my SRAM? (this 
> is also defined in that file).
in your case it will be easier to make the base address 0x80000000 (by
reimplementing the design in EDK) and then you don't have to modify
mbvanilla.h
> 
> c) Does the uClinux compress the kernel and expand it when running - if 
> not, is this an option?
> 
> d) Is it possible to get the impact tool to download data to the SRAM? 
> it is very fast at downloading the ~1MB bistream, so if this was an 
> option perhaps this could be a way of bypassing the ~1 hour kernel 
> download time I am experiencing with XMD & debugger.
you can use the uart as the connection for XMD at 115200bps, I know is
not much but you can download the the image in ~4min 
> 

In my opinion you should modify Dr.John's demo posted on the official
Microblaze uClinux port, by changing the DDR memory contoller with a
SDRAM memory controller keeping the same base_address (0x80000000) and
get rid of the ethernet MAC. I think with this approach you will save
time and ... coffee 

> Cheers & thanks for help
> 
> John
> 
> 
Aurash


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