From: Matt Porter <mporter@kernel•crashing.org>
To: ming lei <mlei30@yahoo•com>
Cc: linuxppc-embedded@ozlabs•org
Subject: Re: MMUCR on ppc440 GP/GX
Date: Mon, 23 May 2005 15:03:22 -0700 [thread overview]
Message-ID: <20050523150322.A17066@cox.net> (raw)
In-Reply-To: <20050523205558.28957.qmail@web61022.mail.yahoo.com>; from mlei30@yahoo.com on Mon, May 23, 2005 at 01:55:58PM -0700
On Mon, May 23, 2005 at 01:55:58PM -0700, ming lei wrote:
> Hi,
>
> I have problem on running system with linuxppc
> 2.4.19(ppc440GP/GX) regarding MMU Control
> Register(MMUCR).
>
> I checked the code in arch/ppc/ there is no code
> setting or unsetting bit 12(DULXE) or bit 13(IULXE),
> but somehow these two bits got changed during boot
> process.
>
> Question 1:
> Does CPU or other hardware change these two bits? If
> linux code doesnt set these two bits initiallt, what's
> the default value? Or I miss something in the code
> that may change these two bits?
>
> Question 2:
> For current 2.4.19 PPC440 implementation, there is no
> special handling for this kind of DataStorage
> exception, is it possible for the user code to stuck
> in this exception forever if these two bits got set in
> MMUCR and the user code calls icbi instruction?
>
> I did a simple test on head_440.S so whenever the
> DataStorage exception happens, in DataStorage assmbly
> code, I clear these two bits in MMUCR, but somehow
> these two bits got set mysteriourly in next exception
> with error_code 0x200000(got from ESR DLK bits).
> What's happening here?
Your kernel revision is very ancient. The problem here is that
you are trying to use _very_ early PPC440 core code I released.
It's filled with critical bugs that were fixed over time. The MMUCR
issue was fixed almost 3 years ago, in fact.
Your best solution is to run a more recent kernel. If that's
not possible, then I suggest you backport all the PPC440
related code from a more recent kernel into your old kernel
base.
-Matt
next prev parent reply other threads:[~2005-05-23 22:03 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-05-23 20:55 MMUCR on ppc440 GP/GX ming lei
2005-05-23 22:03 ` Matt Porter [this message]
-- strict thread matches above, loose matches on Subject: below --
2005-05-24 18:36 ming lei
2005-05-24 20:38 ` Matt Porter
2005-05-24 22:30 ming lei
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