ARM: mpu: Allow enabling of the MPU via kconfig
Allows the user to select MPU support when compiling for ARM processors
that support the PMSAv7.
This ensures that CONFIG_SMP depends on the MPU in the case that no MMU
is present.
CONFIG_SMP_ON_UP is not implemented for nommu, so introduce an MMU
dependency there.
Signed-off-by: Jonathan Austin <jonathan.austin@arm.com>
Reviewed-by: Will Deacon <will.deacon@arm.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 5543d36..ec38cac 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1414,7 +1414,7 @@
depends on CPU_V6K || CPU_V7
depends on GENERIC_CLOCKEVENTS
depends on HAVE_SMP
- depends on MMU
+ depends on MMU || ARM_MPU
select USE_GENERIC_SMP_HELPERS
help
This enables support for systems with more than one CPU. If you have
@@ -1435,7 +1435,7 @@
config SMP_ON_UP
bool "Allow booting SMP kernel on uniprocessor systems (EXPERIMENTAL)"
- depends on SMP && !XIP_KERNEL
+ depends on SMP && !XIP_KERNEL && MMU
default y
help
SMP kernels contain instructions which fail on non-SMP processors.
diff --git a/arch/arm/Kconfig-nommu b/arch/arm/Kconfig-nommu
index c859495..db597e1 100644
--- a/arch/arm/Kconfig-nommu
+++ b/arch/arm/Kconfig-nommu
@@ -50,3 +50,14 @@
Otherwise, say 'y' here. In this case, the kernel will require
external support to redirect the hardware exception vectors to
the writable versions located at DRAM_BASE.
+
+config ARM_MPU
+ bool 'Use the ARM v7 PMSA Compliant MPU'
+ default y
+ help
+ Some ARM systems without an MMU have instead a Memory Protection
+ Unit (MPU) that defines the type and permissions for regions of
+ memory.
+
+ If your CPU has an MPU then you should choose 'y' here unless you
+ know that you do not want to use the MPU.