[PATCH rtems v2 3/7] cpu/armv7m: Add table based init for ARMV7M_MPU

[Sebastian Huber]

On 18/11/2020 15:45, Christian Mauderer wrote:

> +/**
> + * Higher level region configuration.
> + *
> + * Allows to configure with begin and end which is more convenient for
> + * calculating the sizes from linker command file. Note that you still have to
> + * follow the following rules:
> + *
> + * - Begin address has to be aligned to 0x20 (lower 5 bits set to 0)
> + * - Sizes can only be a value of 2^x with a minimum of 32 Byte. If you have an
> + *   end address that is not aligned, the region will get bigger.
> + * - Later regions have higher priority.
> + */
> +typedef struct {
> +  const void *begin;
> +  const void *end;
> +  uint32_t flags;

uint32_t rasr;

I guess the flags are actually a value stored directly to the RASR?

> +} ARMV7M_MPU_Region_Config;

ARMV7M_MPU_Region_config

> +
>   typedef struct {
>     uint32_t dhcsr;
>     uint32_t dcrsr;
> @@ -611,6 +632,85 @@ void _ARMV7M_Supervisor_call( void );
>   
>   void _ARMV7M_Clock_handler( void );
>   
> +static inline uint32_t _ARMV7M_MPU_get_region_size(uintptr_t size)

_ARMV7M_MPU_Get_region_size

> +{
> +  if ((size & (size - 1)) == 0) {
> +    return ARMV7M_MPU_RASR_SIZE(30 - __builtin_clz(size));
> +  } else {
> +    return ARMV7M_MPU_RASR_SIZE(31 - __builtin_clz(size));
> +  }
> +}
> +
> +static inline void _ARMV7M_MPU_set_region(

_ARMV7M_MPU_Set_region

> +  volatile ARMV7M_MPU *mpu,
> +  uint32_t region,
> +  uint32_t rasr,
> +  const void *begin,
> +  const void *end
> +)
> +{
> +  uintptr_t size;
> +  uint32_t rbar;
> +
> +  RTEMS_OBFUSCATE_VARIABLE(begin);
> +  RTEMS_OBFUSCATE_VARIABLE(end);
> +  size = (uintptr_t) end - (uintptr_t) begin;
> +
> +  if ( size > 0 ) {
> +    rbar = (uintptr_t) begin | region | ARMV7M_MPU_RBAR_VALID;
> +    rasr |= _ARMV7M_MPU_get_region_size(size);
> +  } else {
> +    rbar = region;
> +    rasr = 0;
> +  }
> +
> +  mpu->rbar = rbar;
> +  mpu->rasr = rasr;
> +}
> +
> +static inline void _ARMV7M_MPU_disable_region(

_ARMV7M_MPU_Disable_region

> +  volatile ARMV7M_MPU *mpu,
> +  uint32_t region
> +)
> +{
> +  mpu->rbar = ARMV7M_MPU_RBAR_VALID | region;
> +  mpu->rasr = 0;
> +}
> +
> +static inline void _ARMV7M_MPU_setup_from_config_and_enable(
> +  const ARMV7M_MPU_Region_Config *cfg,
> +  size_t cfg_count
> +)

_ARMV7M_MPU_Setup

The config is implicit in the parameter. You don't necessarily enable a configured region. It depends on the user provided RASR value.

> +{
> +  volatile ARMV7M_MPU *mpu;
> +  volatile ARMV7M_SCB *scb;
> +  uint32_t region_count;
> +  uint32_t region;
> +
> +  mpu = _ARMV7M_MPU;
> +  scb = _ARMV7M_SCB;
> +
> +  region_count = ARMV7M_MPU_TYPE_DREGION_GET(mpu->type);
> +
> +  if (cfg_count > region_count) {
> +    rtems_panic("invalid MPU config");
> +  }

I think rtems_panic() is too heavy weight at this point. It uses 
printk(). Maybe just use _Assert(). I think we need some light weight 
general purpose fatal error which could just use the return address to 
identify the error location.

> +
> +  for (region = 0; region < region_count; ++region) {

for (region = cfg_count; region < region_count; ++region)

Only disable not configured regions?

> +    _ARMV7M_MPU_disable_region(mpu, region);
> +  }
> +
> +  for (region = 0; region < cfg_count; ++region) {
> +    _ARMV7M_MPU_set_region(mpu, region, cfg->flags, cfg->begin, cfg->end);
> +  }
> +
> +  mpu->ctrl = ARMV7M_MPU_CTRL_ENABLE | ARMV7M_MPU_CTRL_PRIVDEFENA;
> +  scb->shcsr |= ARMV7M_SCB_SHCSR_MEMFAULTENA;
> +
> +  _ARM_Data_synchronization_barrier();
> +  _ARM_Instruction_synchronization_barrier();
> +}

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