Subject: Re: Advice on adding support for a new Platform
To: John Fremlin <vii@users.sourceforge.net>
From: Richard Earnshaw <rearnsha@buzzard.freeserve.co.uk>
List: port-arm
Date: 06/07/2001 22:26:36
> "Thomas J. Merritt" <tjm@codegen.com> writes:
>
> [...]
>
> > |It's basically a 710T with the fast context switch extension, so
> > |John Fremlin's 7TDMI code should provide all the necessary CPU
> > |support.
> >
> > The 720T extends the ARM7TDMI core with an MMU and a few other
> > goodies.
>
> I'm porting to a 710T, and the so called "7tdmi" code I wrote is for
> the *710T* MMU. As long as the 720T is just a superset of that there
> won't be any hassle until you want to use the extensions . . .
Yep, you should find that, apart from having a different CPU id in CP15
r0, that the 720T is a strict superset of the 710T (at least from a
programmer's point of view).
R.
BTW, I think it is probably a mistake to name some of the cpus after the
basic core name (arm6, arm7, arm8 etc). Cores don't have MMUs or caches,
and NetBSD only runs on a core with a MMU. It would be better to name the
ports after the full cpu-name (6x0, 710, 710T, 920 etc), then it would be
clear that the code works for that core+mmu combination.
Take a look at arm/cpufunc{.c,_asm.S} to see what I mean.