3.9.1. Enabling the MMU

To enable the MMU:

  1. Program the TTB and domain access control registers.

  2. Program level 1 and level 2 page tables as required.

  3. Enable the MMU by setting bit 0 in the control register.

You must take care if the translated address differs from the untranslated address because several instructions following the enabling of the MMU might have been prefetched with the MMU off (using physical = VA - flat translation).

In this case, enabling the MMU can be considered as a branch with delayed execution. A similar situation occurs when the MMU is disabled. Consider the following code sequence:

MRCp15, 0, R1, c1, C0, 0        ; Read control register
ORR R1, #0x1
MCR p15,0,R1,C1, C0,0           ; Enable MMUS
Fetch Flat
Fetch Flat
Fetch Translated

You can enable the ICache and DCache simultaneously with the MMU using a single MCR instruction.

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