Re: [Gumstix-users] Odd problems between Verdex and PDA255 gumstix

[Dave H. <dhy...@gm...>]

Hi David,

> Unfortunately, from what I can see with the XScale architecture, you can
> turn instruction cache on easily, but to turn the data cache on, you
> need to enable the MMU, which then requires virtual addresses.  At the
> moment, I've never dealt with a MMU before so don't know where to start.
> > u-boot could also be doing stuff like turning off caches etc when
> > doing a go command.

I believer that u-boot would use a 1:1 mapping where each virtual
address corresponds to the same physical address.

> > I know that the kernel expects all of the caches to be off.
> >
> >
> Thanks for that info, I'll take a deeper look at u-boot, to try and see
> whether it does anything with the cache.  AFAIK, what I picked up from
> it was that caches were turned off/ignored in the startup code - but I'm
> quite new to all this!

u-boot has two commands: icache and dcache. I see that icache is used
in the default bootcmd just before loading the kernel, but it doesn't
use dcache.

Could you post your actual serial routines?

-- 
Dave Hylands
Vancouver, BC, Canada
http://www.DaveHylands.com/