MMU deactivation and I-Cache / Branch Predictor

Hi !

In order to call some functionality hard-coded in my board ROM (HAB from NXP i.MX6 board), I need to shut down the MMU: the ROM is not position independent. In particular, it is not always possible to map it and the devices correctly due to restriction in my OS.

I order to shutdown the MMU, I started first to shutdown and invalidate the I-Cache, BP and L1/L2 D cache, then I run the ROM code, and then I re-enable everything.

I was wondering if I could keep the I-Cache and BP activated running ROM code, and what was the correct code sequence ? At the moment I do the following:

• Jump to a virtual code region which is mapped as 1:1 with physical addresses
• Disable I Cache & BP
• Invalidate I Cache & BP
• Flush (Clean + Invalidate) L1 D-cache
• Flush (Clean + Invalidate) L2 D-cache
• Disable MMU & L1 D-cache at the same time
• set the stack pointer to a valid physical address
• Disable L2 D-cache
• run the HAB ROM code
• Invalidate I Cache, BP & TLB
• Reactivate I Cache & BP
• Invalidate L1 / L2 D-cache
• Reactivate L2 D-cache
• Reactivate L1 D cache & MMU at the same time
• restore virtual stack pointer
• jump back to my OS

I think I still need to invalidate I cache & BP before shutting down the MMU, but could I keep them enabled ? Or should I reenable them before calling the HAB ROM code ?

Best,

Vincent