[U-Boot] boot from ram on rd-6281-a

[Juergen Schindele]

Am Freitag, 26. Februar 2010 schrieben Sie:
> Dear Juergen,
> 
> On Fri, Feb 26, 2010 at 12:16:22PM +0100, Juergen Schindele wrote:
> > Am Freitag, 26. Februar 2010 schrieb Wolfgang Denk:
> > > Dear Juergen Schindele,
> > > 
> > > In message <201002261056.32502.schindele at nentec.de> you wrote:
> > > >
> > > > i need a different bootloader than the one installed.
> > > > so i tried to develop a private one by loading it to RAM.
> > > > So i modified the TEXT_BASE = 0x00400000
> > > > to not collide with the installed one.
> > > 
> > > This is not enough. You must also make sure not to try to perform all
> > > the low level initializations again that have already been done.
> > I know that, but SKIP_LOW_LEVEL_INIT is defined because 
> > register init is done with kirkwood boot header for booting from
> > SPI/NAND-Flash. I dont see other blocking points. :-(
> > i tried to skip relocate too but it did not help !
> 
> I have absolutely no experience concerning kirkwood, but did the same
> for coldfire for running U-Boot as the flasher application started
> from the debugger...
> IIRC there were three places I had to change for coldfire:
> - low-level init: do not put the vector table at the beginning
>   of code (probably better: initialize it in the proper place?)
> - leave the vector base register as it is (should be set up
>   properly by first loader/debugger, and U-Boot does not use
>   interrupts)
> - the cpu speed detection/setting code was basically switched back to
>   detection for CONFIG_MONITOR_IS_IN_RAM because it involved putting
>   the RAM to self-refresh, which is obviously not possible when running
>   from it
> 
> (For Coldfire, a special case was that I had to disable monitor
> protection manually because the standard condition fails due to the
> memory layout.)
Thanks for your hint. It lead me to comment out "kirkwood_mpp_conf"
in function "board_init" and now it works quite great like expected.
In my understanding the mpp configuration of  rd6281a is buggy !?

we'll see in furter tests.
> Here's my patch for Coldfire MCF532x/7x:
> http://www.mail-archive.com/u-boot@lists.denx.de/msg28779.html
> 
> BTW, disabling relocation may lead to bad results for malloc and
> the initial stack setup. I am not sure but seem to remember I
> had some problems when I tried it - and, it should not be a problem
> to do it as usual anyways if everything else is working correctly.
> 
> Hope this can give some useful hints,
> Wolfgang
> 
> 
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Jürgen Schindele  
Software-Entwicklung

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