Where is MMU enabled?

Where is MMU enabled?

[Rick Brown]

Hi List,

I am curious to know where is the MMU turned on in a Linux PPC system
- is it the u-boot or the linux kernel? Since enabling of MMU shall be
the point from where the CPU will have to generate virtual addresses -
I think it should be somewhere in the kernel. The reason is that all
the addresses that we give on the u-boot command line are physical
addresses and not virtual, right (Thus implying MMU is not turned
on?)?

Or is it that kernel always gets the control with MMU on on PPC systems?

How about other architectures?

Thanks,

Rick
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Re: Where is MMU enabled?

[hmthalib]

Rick Brown wrote:
> Hi List,
> 
> I am curious to know where is the MMU turned on in a Linux PPC system
> - is it the u-boot or the linux kernel?


It is Linux. u-boot uses the flat memory system.

  Since enabling of MMU shall be
> the point from where the CPU will have to generate virtual addresses -
> I think it should be somewhere in the kernel. The reason is that all
> the addresses that we give on the u-boot command line are physical
> addresses and not virtual, right (Thus implying MMU is not turned
> on?)?

yes. MMU is not turned on in u-boot

compare the data sheet and head_32.S for powerpc arch to know how the 
MMU is initialized .

> 
> Or is it that kernel always gets the control with MMU on on PPC systems?
> 
> How about other architectures?
> 
> Thanks,
> 
> Rick
> 
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Regards,
Mohamed Thalib H
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