Re: Regarding MPC8641D

[sivaji <rameshmrm@gmail.com>]

Hi,
           We need only SMP mode, asper ur idea let me disable the Low
memory offset mode. We face some issues when ioremap in the kernel, we guess
the problem is related to Low memory offset mode so only we go for that.
Consider now the Low memory offset is disable the bootargs (root=/dev/ram
console=ttyS0, mem=504M). When mem=504 or greater than  we are not able to
ioremap, if mem is less than 500 there was no issues on ioremap. We can't
understand why ioremap was failed for 504M?

Thanks and Regards
S.Balamurugan


Siva Prasad-3 wrote:
> 
> Hi,
> 
> If you want to use SMP, do not enable low memory offset mode. That is
> only and only for AMP, not for SMP. All the exception vectors go into a
> different address range for core1, once you enable that, resulting in a
> need for entirely different copy of OS (be it Linux, or any other OS).
> 
> You are in the right path. Just don't enable low memory offset mode,
> unless you are looking for Assymetric multi-processing.
> 
> - siva
> 
> 
> 
> 
> Message: 6
> Date: Wed, 5 Dec 2007 16:45:31 -0800 (PST)
> From: sivaji <rameshmrm@gmail.com>
> Subject: Re: Regarding MPC8641D
> To: linuxppc-dev@ozlabs.org
> Message-ID: <14184234.post@talk.nabble.com>
> Content-Type: text/plain; charset=us-ascii
> 
> 
> Hai,
>              The kernel was compiled in SMP mode. The low memory offset
> mode
> is only for AMP mode means, then how we test both the core 0 and 1 in
> the
> linux kernel ?. Asper my understanding if we enable the Low Memory
> Offset
> mode, then only the core1 translation is enabled. If we disalbed the Low
> Memory offset mode, Only Core 0  will work in SMP mode and Core 1 will
> idle.
> If we want to test the efficient of Dual core means we need to enable
> both
> the core and Low Memory Offset Mode. For this configuration linux kernel
> was
> not up.
> ( Please correct me if I am wrong )
> 
> Thanks and Regards
> Sivaji
> 
> 
> Chris Fester wrote:
>> 
>> On Tue, 2007-12-04 at 23:51 -0800, sivaji wrote:
>>>             We have designed  a MPC8641D based AMC card. We are using
> the
>>> kernel (2.6.23-rc4) and uboot (1.2.0).  When we disable the core1 Low
>>> Memory
>>> offset mode the kernel was up and when we enable this core1 Low
> Memory
>>> offset mode kernel was not up, It was hang after MPIC initialization.
>> [snip!]
>>>                      After this the kernel was hang, i want to know
> why
>>> kernel was hang when we enalbe Low memory Offset mode. Please help me
> to
>>> fix
>>> this issue.
>> 
>> Have you compiled your kernel for SMP mode?  I believe the Low memory
>> offset mode is only for AMP mode (vxworks can use this, probably other
>> OSes).  I don't know if the kernel has support for any multiprocessing
>> mode other than SMP.
>> 
>> Hope that helps,
>> Chris
>> 
> 
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> 

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