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SubjectRe: bcm33xx port
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On Sunday 08 June 2008, Maciej W. Rozycki wrote:
> On Sun, 8 Jun 2008, Luke -Jr wrote:
> > the bcm63xx patches OpenWrt has that I'm using as a base for this...
>
> It would be best if the patches you are referring to got merged with the
> mainline. Otherwise whoever uses them is essentially on their own --
> people lack the resources needed to chase random changes out there in
> general.

Is merging with mainline something I can help with, being a beginner in this
area generally and not having any part in writing them?

> > > That's grossly wrong. If you need to preset it for the time being
> > > till you debug calibration, then for a MIPS processor assume one
> > > instruction per clock tick and two instructions per loop -- that may
> > > not be entirely correct, but is a good approximation. Otherwise you
> > > risk peripheral devices are not driven correctly with all sorts of the
> > > nasty results.
> >
> > Meaning this?
> > preset_lpj = loops_per_jiffy = 2;
>
> Not exactly. Try harder -- this is simple arithmetic and you've got all
> the data given above already. :)

200 / 2? I'm not really sure what a 'jiffy' is..

> > > and (b) control being transferred to a block of memory that isn't
> > > actually code, as can happen if exception vectors or global
> > > pointers-to-functions aren't set up correctly, or if the kernel stack
> > > is being corrupted. When you say "the instruction in question is a
> > > store word", how do you know that?
> >
> > The RI error spits out a bunch of info, including epc which presumably
> > points to the instruction causing the problem: ac85ffc0; this is 'sw
> > a1,-64(a0)'
>
> I have seen that already and wrote these stores in __bzero are protected.
> Perhaps the fixup fails for some reason, but you need to investigate it
> and this is why I suggested to see how the RI handler is reached. Since
> this is a known point the failure leads to, you should be able to work
> backwards from there quite easily.

Ah, so what you're saying is that perhaps the 'sw' is triggering a TLB
exception, and the handler for *that* is causing the RI problem?

Thanks,

Luke


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