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Re: CONFIG_MIPS_UNCACHED

To: "Kevin D. Kissell" <kevink@mips.com>
Subject: Re: CONFIG_MIPS_UNCACHED
From: Jun Sun <jsun@mvista.com>
Date: Sun, 24 Jun 2001 21:42:32 -0700
Cc: linux-mips@oss.sgi.com
In-reply-to: <020c01c0fc21$51256760$0deca8c0@Ulysses>; from kevink@mips.com on Sat, Jun 23, 2001 at 10:15:49PM +0200
References: <3B34BE3B.B72D40F1@mvista.com> <01ee01c0fc08$66e81e80$0deca8c0@Ulysses> <3B34D6AC.9EACA819@mvista.com> <020c01c0fc21$51256760$0deca8c0@Ulysses>
Sender: owner-linux-mips@oss.sgi.com
User-agent: Mutt/1.2.5i
On Sat, Jun 23, 2001 at 10:15:49PM +0200, Kevin D. Kissell wrote:
> > > Since the kernel cache attribute is never initialized before
> > > ld_mmu_{whatever} is invoked, and since that Config field
> > > does not have a well-defined reset state on many MIPS
> > > CPUs, it would appear that we are in effect trusting the
> > > bootloader to have done something reasonable like
> > > set kseg0 to be non-cachable or write-through, either
> > > of which would be safe for the current code.
> >
> > I think you just proposed a fix: check current config register when we
> turn
> > off cache.  Thanks. :-)
> 
> That's a heuristic at best.  If the config register comes up random,
> it can appear to be sane even though the cache is in fact uninitialized.
> 

For any practical reasons, we can assume there is a loader for Linux,
and we can assume loader does not run with a random config register.

Jun

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