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Message-ID: <020c01c0fc21$51256760$0deca8c0@Ulysses>
From: "Kevin D. Kissell" <kevink@mips.com>
To: "Jun Sun" <jsun@mvista.com>
Cc: <linux-mips@oss.sgi.com>
References: <3B34BE3B.B72D40F1@mvista.com> <01ee01c0fc08$66e81e80$0deca8c0@Ulysses> <3B34D6AC.9EACA819@mvista.com>
Subject: Re: CONFIG_MIPS_UNCACHED
Date: Sat, 23 Jun 2001 22:15:49 +0200
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> > 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.

            Kevin K.

From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <020c01c0fc21$51256760$0deca8c0@Ulysses>
From: "Kevin D. Kissell" <kevink@mips.com>
References: <3B34BE3B.B72D40F1@mvista.com> <01ee01c0fc08$66e81e80$0deca8c0@Ulysses> <3B34D6AC.9EACA819@mvista.com>
Subject: Re: CONFIG_MIPS_UNCACHED
Date: Sat, 23 Jun 2001 22:15:49 +0200
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	charset="iso-8859-1"
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Sender: owner-linux-mips@oss.sgi.com
To: Jun Sun <jsun@mvista.com>
Cc: linux-mips@oss.sgi.com
Message-ID: <20010623201549.wTv7J4kp9R42HOEYEmLOhca_QDcDpZhaTAy719zV3YI@z>

> > 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.

            Kevin K.