Subject: Re: Acorn32 start.S
To: Gavan Fantom <gavan@coolfactor.org>
From: Reinoud Zandijk <reinoud@netbsd.org>
List: port-arm
Date: 07/03/2007 18:30:05
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Dear Gavan,

On Tue, Jul 03, 2007 at 05:23:55PM +0100, Gavan Fantom wrote:
> >i'm confused about the correct procedure concerning MMU disabling on ARMv3 
> >and ARMv4. The data sheets i have for ARM610/ARM710 and SA don't mention 
> >what effect it will have on the instruction fetching. AFAIK its two 
> >instructions that are in the pipeline before the translation becomes 
> >effective.
> >
> >The offending code is in src/sys/arch/acorn32/stand/boot32/start.S around 
> >line 83. Will the following patch fix the problem? or is something really 
> >wrong and should i split off ARMv3 and ARMv4 mmu disable code?
> 
> What is the problem you are trying to fix?

erradic booting problems on various machines; some work and bootup NetBSD 
fine and others never make it into kernel code it appears. I think it might 
be due to interaction between MMU, D&I caches etc. that it sometimes works 
and otherwise not and might be as simple as does the code start in a cache 
line or not etc.

So i'd rather fix it for once and for all :)

Cheers,
Reinoud

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