[U-Boot] PPC440GX TLB setting problem.

[Stefan Roese]

Hi Wouter,

On Thursday 23 July 2009 20:39:44 Wouter Eckhardt wrote:
> I'm working on trying to get VxWorks to boot on a PPC440GX processor
> using U-Boot, using an ALPR board. In order to boot VxWorks properly (it
> expects caching on the SDRAM to be disabled), I created a new board
> directory and such (based on the ALPR board), and then changed the TLB
> settings in init.S.

Are you sure that the cache needs to be disabled? Perhaps it just needs to get 
properly flushed before booting VxWorks? Just checking.

> My problem is that when my new U-Boot has booted, the TLBs are not
> configured as I have programmed them. I verified this using a BDI
> debugger. The TLB settings are still the same as the settings the
> original ALPR U-Boot used. I'm really at a loss here. It seems that no
> matter what I try (I tried quite a few variantions of the TLB settings),
> the TLB settings won't change.
>
> So now I several, related, questions:
> - What could be the cause of this? Have I done something wrong?

This could have multiple reasons. Are you sure that you are running the 
freshly compiled image on the board? Did you check the build time?

> - Is U-Boot reconfiguring the TLBs after init.S has executed?

Yes. But only one (IIRC). The first TLB for bootrom access. Caching will be 
disabled before relocating to SDRAM.

> - If so, how can I control those TLBs?

All other TLB's should be the same.

Not sure what's going wrong here.

Best regards,
Stefan

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