[ECOS] RedBoot in Little Endian Mode

Mark Salter msalter@redhat.com
Thu Feb 17 19:11:00 GMT 2005


On Thu, 2005-02-17 at 21:26 +0300, Nickolay wrote:
> Mark Salter wrote:
> 
> >On Thu, 2005-02-17 at 21:00 +0300, Nickolay wrote:
> >  
> >
> >>Hello Guys!
> >>
> >>I has IXDP425 board, and should running her in Little Endian mode.
> >>I download redboot BE and LE ROM image from Intel, but has some trouble 
> >>with NPE network card working in LE mode.
> >>    
> >>
> >
> >This could be a problem with the CPU. Early (A-step) CPUs do not
> >correctly support LE mode. This only really shows up in the NPE
> >ethernet support. Look at the CPU on your board and see if it is
> >marked "IXP425AD" (A-step) or "IXP425BD" (B-step). A-step will
> >not support NPE in LE mode.
> >
> >--Mark
> >
> >
> >
> >  
> >
> Yeah, CPU marked IXP425AD.
> But i can't understand, really it is impossible to fix it(LE/BE 
> conversion) in the NPE-ethernet driver?
> Why not?

The B-step and later CPUs support a "data coherent" attribute
bit in page table entries. This bit controls how the CPU views
the LE memory area covered by the page table section entry.
The networking support for NPE relies on this special view
into memory, but the A-step CPUs cannot provide this.

I wouldn't say it is impossible to get around this, but it
isn't worth the effort to support the original run of CPUs.

--Mark




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