[U-Boot-Users] Re: U-boot environment in Xilinx System ACE?

[Keith J Outwater]

Hi Wolfgang - 

wd at denx.de wrote on 07/07/2005 01:00:41 PM:
> Dear Keith,
> 
> in message <OFD86B567B.6DB5DBFC-ON07257037.005D553D-07257037.
> 005E4D94 at mck.us.ray.com> you wrote:
> >
> > The nature of the design requires that the Xilinx System ACE compact 
flash 
> > card be the only nonvolatile memory on the board - no plain old FLASH 
> > memory or I2C EEPROM.  Therefore, I would like to store the U-Boot 
> > environment as a file on the compact flash card.
> 
> This has been discussed before...

I thought as much.  I just makes too much sense :)

> 
> > I have checked the latest CVS sources and it appears that no one has 
> > implemented this yet.
> 
> Right.
> 
> > Before I take a crack at it, is anyone planning to do this or in the 
> > process of doing it?  Does anyone have any advice or caveats?
> 
> This is not trivial to handle. The environment needs to  be  accessed
> very,  very  early  in  initialization - to read the console baudrate
> when starting the console driver. IDE /  CompactFlash  on  the  other
> hand  gets  initialized  much,  much later, long after relocating the
> whole stuff to RAM.
> 
> I don't see how these two situations mix easily.  Can  you  attach  a
> EEPROM via I2C or so?

I would prefer to do it that way, but the hardware must not be able to
store any data on-board.  All nonvolatile storage must be "removable"
as in physical removal.

I did remember that the u-boot environment was read very early and it
sounds like the restricted runtime environment was the reason that
storing then environment in compact flash was not implemented.

If the problem is RAM, then I can solve that by dedicating some
internal RAM in the FPGA for stack and data.  Could we also use
the PPC405 caches?

> 
> Best regards,
> 
> Wolfgang Denk