[U-Boot] Segmented RAM, big userspace.

[Wolfgang Denk]

Dear Sergey Lapin,

In message <20111213160810.GA27440 at build.ihdev.net> you wrote:
> 
> We have a board, based on s3c2416, with 128MB of RAM
> and 1GB of NAND flash.
> RAM is organized as 2 memory banks with far placed bases:
> TOP
> UNUSED 64MB
> 64MB SDRAM
> --- 128MB segment base 1 -----
> UNUSED 64MB
> 64MB SDRAM
> -- 128MB segment base 0 ------
> BOTTOM
> 
> So we could have only 64MB as one piece; Due to u-boot reloaction code we
> need to have u-boot in first 64MB also. ...

Why would that be the case?

I would expect that U-Boot (with all it's heap and stack and
everything) sits only at the upper end of the upper bank of memory (in
your sgment 1).

>                                   ... . And now we have root filesystem
> which we need to flash using u-boot, which is a little over this 64MB limit.

Split it?

> Is there some way to use second memory bank from u-boot?
> Is it possible to tftp file in parts and flash it on NAND in parts?
> (This requires handling of bad blocks too)
> 
> We need to flash using u-boot, that's requirement for speedy production.

I somewhat doubt that. Booting Linux is probably a matter of 2 or 3
seconds, or less.  You migth save that time again by using Linux' much
better performing network stack, together with interleaving network
traffic and flash writing.

If I were in this situation, I'd probably run this under Linux.

Best regards,

Wolfgang Denk

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