[PATCH 0/7] ARM: NOMMU: MPU updates

[Alexandre Torgue]

Hi Vlad,

On 06/13/2017 11:05 AM, Vladimir Murzin wrote:
> Hi,
> 
> This is an update of the existent MPU code which consist set of
> clean-ups and enhancements. The most significant changes are in the way
> how MPU settings sync-up for secondaries (PATCH 3/7) and more flexible
> layout for memory (PATCH 7/7). Since there is no in-tree user of MPU,
> support for M-class has been added (PATCH 6/7).
> 
> Thanks!
> 
> Changelog:
> 
>          RFC v2 -> v1
>                 - dropped RFC tag
> 	       - Tested-by from András
> 	       - rebased on 4.12-rc5
> 
>             RFC -> RFC v2
> 	       - fixed MPU enable for v7m (PATCH 6/7)
> 
> Vladimir Murzin (7):
>    ARM: NOMMU: Move out MPU setup in separate module
>    ARM: NOMMU: Update MPU accessors to use cp15 helpers
>    ARM: NOMMU: Rework MPU to be mostly done in C
>    ARM: NOMMU: Disallow MPU for XIP
>    ARM: Kconfig: Kill CONFIG_VECTORS_BASE
>    ARM: V7M: Add support for MPU to M-class
>    ARM: NOMMU: Use more MPU regions to cover memory
> 
>   arch/arm/Kconfig               |   9 -
>   arch/arm/Kconfig-nommu         |   4 +-
>   arch/arm/include/asm/cputype.h |  10 +
>   arch/arm/include/asm/mpu.h     |  23 ++-
>   arch/arm/include/asm/smp.h     |   2 +-
>   arch/arm/include/asm/v7m.h     |  10 +
>   arch/arm/kernel/asm-offsets.c  |  11 +
>   arch/arm/kernel/head-nommu.S   | 128 +++++++++---
>   arch/arm/kernel/smp.c          |   2 +-
>   arch/arm/mm/Makefile           |   1 +
>   arch/arm/mm/nommu.c            | 254 +----------------------
>   arch/arm/mm/pmsa-v7.c          | 445 +++++++++++++++++++++++++++++++++++++++++
>   12 files changed, 598 insertions(+), 301 deletions(-)
>   create mode 100644 arch/arm/mm/pmsa-v7.c
> 

I tested two cases on stm32h743 (based on cortes-M7):

  - NO XIP: it works fine.
  - XIP: it is ko Kernel doesn't boot.

I started investigations but no big success.
I have a question:
In arch/arm/kernel/head-nommu.S, I see that background region is set 
after the XIP region. It seems due to save CPU register value. But doing 
that you remove the XIP region just created. No ?

Other point, why (in arch/arm/kernel/head-nommu.S) we couldn't create:

1-backup region strongly-ordered
2-create SDRAM region (normal one)
3-create XIP region

By debugging I saw that issue was due to the backup region. If I remove, 
backup region settings done by Kernel, and I put the sequence above in 
my bootloader, it works fine in XIP.

Sorry to not have more precise analysis.

Regards
Alex