[U-Boot] [PATCH v2] ppc4xx: Add Sequoia RAM-booting target

[Stefan Roese]

On Monday 11 May 2009 15:20:10 Wolfgang Denk wrote:
> > > And what happens when the TLB is not correctly set? Will we get a
> > > useful error message then?
> >
> > No. SDRAM needs to work correctly so that this RAM-booting version can
> > function. And for this the MMU needs to be configured and the SDRAM
> > controller setup correctly. If this is not the case and SDRAM is not
> > working from the debugger then we have no chance to load this image
> > without problems (verify will most likely fail) or run it.
>
> Hm... if the image cannot run anyway without initialized SDRAM TLB,
> then why do you scan for it?  My understanding is that the result
> wouldbe the same even if you omitted this test: without initialized
> SDRAM TLB the system would just hang / crash without error message.
> So this test is dead code.
>
> Or am I missing something?

I'm "scanning" for the SDRAM TLB, because it can be on any TLB location. In my 
first implementation I assumed that the SDRAM TLB was TLB #0 (configured via 
BDI2000). This worked just fine. But then I loaded this RAM-booting image via 
U-Boot and started it here (via go ...). And it crashed since U-Boot uses a 
different TLB #. So now I'm scanning/detecting the SDRAM TLB to be independent 
from the originator of the TLB. 

Best regards,
Stefan

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