[U-Boot] PPC440GX TLB setting problem.

[Stefan Roese <sr@denx.de>]

Hi Wouter,

On Friday 24 July 2009 09:48:17 Wouter Eckhardt wrote:
> Yes, I've checked the VxWorks kernel code. The comments mention that if
> caching is enabled, the cache should be flushed before the call to MMU
> TLB initialization is done. However, the calling code never actually
> flushes the cache. So they're not even following their own advice. In
> the calling code, they just assume that caching is disabled.

OK.

> > > - 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.
> Hmmm. This should be a problem since I changed the TLB settings to have
> SDRAM at the first TLB. However, the SDRAM gets remapped in a different
> TLB as well. Where in the code can I find this? I tried looking for
> something like that, but couldn't find it. Perhaps that piece of code is
> actually replacing all TLBs, not just the bootrom access one.

Take a look at Sequoia. It has support for VxWorks booting. You need to switch 
the sequence of the TLB entries. init.S:

	/* vxWorks needs this as first entry for the Machine Check interrupt */
	tlbentry( 0x40000000, SZ_256M, 0, 0, AC_R|AC_W|AC_X|SA_G|SA_I )

And you need to set CONFIG_SYS_TLB_FOR_BOOT_FLASH in your board config header 
to the number of the boot TLB entry.

Let me know if this helps.

Best regards,
Stefan

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