From: "mojtaba" <kernelppc@gmail.com>
To: "'Sergey Temerkhanov'" <temerkhanov@yandex.ru>,
<linuxppc-embedded@ozlabs.org>
Subject: RE: Instruction OCM
Date: Tue, 20 May 2008 11:19:26 +0200 [thread overview]
Message-ID: <016b01c8ba5a$9a621000$cf263000$@com> (raw)
In-Reply-To: <4831CCA2.6000107@yandex.ru>
Thank you for your email. But what is the solution to that? I have seen this
in a thesis:
"when using the OCM buses to connect memory, we can only use virtual memory
as long as the virtual address is the same as the physical address, which is
conceptually
the same as using a system without MMU. Therefore porting Linux to a
system based on an OCM memory system is not possible"
http://ce.et.tudelft.nl/publicationfiles/1367_700_thesis.pdf
Is that right? What do you suggest?
-----Original Message-----
From: linuxppc-embedded-bounces+kernelppc=gmail.com@ozlabs.org
[mailto:linuxppc-embedded-bounces+kernelppc=gmail.com@ozlabs.org] On Behalf
Of Sergey Temerkhanov
Sent: Monday, May 19, 2008 8:53 PM
To: linuxppc-embedded@ozlabs.org
Subject: Re: Instruction OCM
mojtaba wrote:
>
> Dear all,
>
> I cannot run Linux when I have an instruction OCM in my design but,
> without instruction OCM everything is fine. I tried to do some
> debugging. It seems that the Linux memory management unit has a
> problem with that. After entering the MMU initialization phase, it
> suddenly jumps to address 0x00000700 it get stuck there. Is there
> anybody who have tried a design with instruction OCM? Do I need to do
> special configuration for the Linux kernel?
>
> Regards,
>
> Mojtaba
>
> ------------------------------------------------------------------------
>
> _______________________________________________
> Linuxppc-embedded mailing list
> Linuxppc-embedded@ozlabs.org
> https://ozlabs.org/mailman/listinfo/linuxppc-embedded
Address 0x700 means invalid opcode exception.
If instruction OCM is same as data OCM (I think it's so) then any MMU
mapping is not applicable to this region at all as OCM controller
decodes virtual addresses bypassing any MMU mappings.
In your situation MMU maps virtual address of OCM to physical address
containing some random data and CPU tries to execute it. So you get
invalid opcode exception.
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next prev parent reply other threads:[~2008-05-20 9:18 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-19 15:17 Instruction OCM mojtaba
2008-05-19 16:58 ` Stephen Neuendorffer
2008-05-20 8:31 ` mojtaba
2008-05-19 17:59 ` Koss, Mike (Mission Systems)
2008-05-19 18:53 ` Sergey Temerkhanov
2008-05-20 9:19 ` mojtaba [this message]
2008-05-20 11:11 ` Temerkhanov
2008-05-20 21:26 ` Stephen Neuendorffer
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