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imxrt:mpu init handle dcache setting in MPU config

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With CONFIG_ARMV7M_DCACHE the cache maintenance operation
   are not present. Or if CONFIG_ARMV7M_DCACHE_WRITETHROUGH
   is on then buffering operations are no-ops.

   This change enables MPU_RASR_C and MPU_RASR_B if
   CONFIG_ARMV7M_DCACHE is only set.

   if CONFIG_ARMV7M_DCACHE_WRITETHROUGH is set then only
   MPU_RASR_C is enabled.

   N.B When caching is disalbed unaligned access may cause hard faults
   so add -mno-unaligned-access

   It is always safe to enable Buffering in FLASH to achive unaligned
   access leniency, as it is not written to.
This commit is contained in:
David Sidrane 2021-10-27 07:21:01 -07:00 committed by Xiang Xiao
parent 7e9e8a817d
commit 08d0434bad
1 changed files with 25 additions and 0 deletions
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25
arch/arm/src/imxrt/imxrt_mpuinit.c
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@ -49,6 +49,31 @@
# define MIN(a,b) a < b ? a : b
#endif
#ifndef CONFIG_ARMV7M_DCACHE
/* With Dcache off:
* Cacheable (MPU_RASR_C) and Bufferable (MPU_RASR_B) needs to be off
*/
# undef MPU_RASR_B
# define MPU_RASR_B 0
# define RASR_B_VALUE 0
# define RASR_C_VALUE 0
#else
# ifndef CONFIG_ARMV7M_DCACHE_WRITETHROUGH
/* With Dcache on:
* Cacheable (MPU_RASR_C) and Bufferable (MPU_RASR_B) needs to be on
*/
# define RASR_B_VALUE MPU_RASR_B
# define RASR_C_VALUE MPU_RASR_C
# else
/* With Dcache in WRITETHROUGH Bufferable (MPU_RASR_B)
* needs to be off, except for FLASH for alignment leniency
*/
# define RASR_B_VALUE 0
# define RASR_C_VALUE MPU_RASR_C
# endif
#endif
/****************************************************************************
* Public Functions
****************************************************************************/