[U-Boot-Users] 5282 u-boot shadowing

[U-Boot-Users] 5282 u-boot shadowing

[NZG]

I'm working on getting u-boot up and running, pre-loader less, for the 5282.
I've run into a few issues with the way things are currently done and I wanted 
to run some alternatives past the list to make sure I'm not violating any 
u-boot standards.

1. The m68k code currently copies it's flash to DRAM at it's final location, 
then jumps to DRAM.
To do it this way, the DRAM cannot be located at 0, as initializing the RAM 
there will shadow the Flash before the code has been copied. 

Therefore the RAM can either be
1. moved to another location - I have implemented a version that does this, 
and it starts up ok, but the RAM winds up being at location 0xff000000, 
rather than 0. Is this going to work? Or am I violating some important 
standard?

2. Copied before the address of the RAM is set, then just drop the RAM 
directly on top of it. I haven't tried this yet, but it may be a better 
solution as I'm getting the feeling that u-boot is expecting RAM at 0.
Is this correct?


thx,
NZG.

[U-Boot-Users] 5282 u-boot shadowing

[Zachary Landau]

On Tue, 15 Mar 2005 11:50:34 -0600, NZG <ngustavson@emacinc.com> wrote:
> I'm working on getting u-boot up and running, pre-loader less, for the 5282.
> I've run into a few issues with the way things are currently done and I wanted
> to run some alternatives past the list to make sure I'm not violating any
> u-boot standards.

Maybe you didn't get my previous email to you about this.  I got the
5282 running pre-loader less in u-boot.  Some of the necessary changes
I have posted as patches to the mailing list.  A few of the changes
(like for the FLASH support) required some changes that changed u-boot
too much, so they still need to be reworked.  It still has some
issues, so don't expect all of this to work right away.   My webspace
isn't working properly, so I'll put the code up there a bit later.

> 
> 1. The m68k code currently copies it's flash to DRAM at it's final location,
> then jumps to DRAM.
> To do it this way, the DRAM cannot be located at 0, as initializing the RAM
> there will shadow the Flash before the code has been copied.

I have the linker setup the flash at 0xf0000000.  When booting up,
before setting the FLASHBAR, the flash is seen as being at 0x0.  So,
first, I jump to 0x400 instead of 0xf000400.  I then copy into the
internal SRAM code to set the flash bar and then jump to the proper
location.  There may be a cleaner way, but that worked for me.  I'll
attach cpu/mcf52x2/start.S so you can see how I did it.

-- 
Zachary P. Landau <kapheine@gmail.com>
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