Hi Kerry,
I mean all the Example Projects in the SDK that I have looked at are wrong. Here is one from evkmimx1020->rtos_examples->freertos_generic.
I think I used this as my base project.
board.c:
/* MPU configuration. */
void BOARD_ConfigMPU(void)
{
/* Disable I cache and D cache */
if (SCB_CCR_IC_Msk == (SCB_CCR_IC_Msk & SCB->CCR)) {
SCB_DisableICache();
}
if (SCB_CCR_DC_Msk == (SCB_CCR_DC_Msk & SCB->CCR)) {
SCB_DisableDCache();
}
/* Disable MPU */
ARM_MPU_Disable();
/* Region 0 setting */
MPU->RBAR = ARM_MPU_RBAR(0, 0xC0000000U);
MPU->RASR = ARM_MPU_RASR(0, ARM_MPU_AP_FULL, 2, 0, 0, 0, 0, ARM_MPU_REGION_SIZE_512MB);
/* Region 1 setting */
MPU->RBAR = ARM_MPU_RBAR(1, 0x80000000U);
MPU->RASR = ARM_MPU_RASR(0, ARM_MPU_AP_FULL, 2, 0, 0, 0, 0, ARM_MPU_REGION_SIZE_1GB);
/* Region 2 setting */
#if defined(XIP_EXTERNAL_FLASH)
MPU->RBAR = ARM_MPU_RBAR(2, 0x60000000U);
MPU->RASR = ARM_MPU_RASR(0, ARM_MPU_AP_FULL, 0, 0, 1, 1, 0, ARM_MPU_REGION_SIZE_512MB);
#else
MPU->RBAR = ARM_MPU_RBAR(2, 0x60000000U);
MPU->RASR = ARM_MPU_RASR(0, ARM_MPU_AP_FULL, 2, 0, 0, 0, 0, ARM_MPU_REGION_SIZE_512MB);
#endif
/* Region 3 setting */
MPU->RBAR = ARM_MPU_RBAR(3, 0x00000000U);
MPU->RASR = ARM_MPU_RASR(0, ARM_MPU_AP_FULL, 2, 0, 0, 0, 0, ARM_MPU_REGION_SIZE_1GB);
/* Region 4 setting */
MPU->RBAR = ARM_MPU_RBAR(4, 0x00000000U);
MPU->RASR = ARM_MPU_RASR(0, ARM_MPU_AP_FULL, 0, 0, 1, 1, 0, ARM_MPU_REGION_SIZE_128KB);
/* Region 5 setting */
MPU->RBAR = ARM_MPU_RBAR(5, 0x20000000U);
MPU->RASR = ARM_MPU_RASR(0, ARM_MPU_AP_FULL, 0, 0, 1, 1, 0, ARM_MPU_REGION_SIZE_128KB);
/* Region 6 setting */
MPU->RBAR = ARM_MPU_RBAR(6, 0x20200000U);
MPU->RASR = ARM_MPU_RASR(0, ARM_MPU_AP_FULL, 0, 0, 1, 1, 0, ARM_MPU_REGION_SIZE_256KB);
/* The define sets the cacheable memory to shareable,
* this suggestion is referred from chapter 2.2.1 Memory regions,
* types and attributes in Cortex-M7 Devices, Generic User Guide */
#if defined(SDRAM_IS_SHAREABLE)
/* Region 7 setting, set whole SDRAM can be accessed by cache */
MPU->RBAR = ARM_MPU_RBAR(7, 0x80000000U);
MPU->RASR = ARM_MPU_RASR(0, ARM_MPU_AP_FULL, 0, 1, 1, 1, 0, ARM_MPU_REGION_SIZE_32MB);
#else
/* Region 7 setting, set whole SDRAM can be accessed by cache */
MPU->RBAR = ARM_MPU_RBAR(7, 0x80000000U);
MPU->RASR = ARM_MPU_RASR(0, ARM_MPU_AP_FULL, 0, 0, 1, 1, 0, ARM_MPU_REGION_SIZE_32MB);
#endif
/* Region 8 setting, set last 2MB of SDRAM can't be accessed by cache, glocal variables which are not expected to be accessed by cache can be put here */
MPU->RBAR = ARM_MPU_RBAR(8, 0x81E00000U);
MPU->RASR = ARM_MPU_RASR(0, ARM_MPU_AP_FULL, 1, 0, 0, 0, 0, ARM_MPU_REGION_SIZE_2MB);
/* Enable MPU */
ARM_MPU_Enable(MPU_CTRL_PRIVDEFENA_Msk);
/* Enable I cache and D cache */
SCB_EnableDCache();
SCB_EnableICache();
}
You can see that the memory sizes for ITCM, DTCM and OCRAM are incorrect.
I found a few other things that I thought were incorrect.
This is my version:
/* MPU configuration. */
void BOARD_ConfigMPU(void)
{
/* Disable I cache and D cache */
if (SCB_CCR_IC_Msk == (SCB_CCR_IC_Msk & SCB->CCR)) {
SCB_DisableICache();
}
if (SCB_CCR_DC_Msk == (SCB_CCR_DC_Msk & SCB->CCR)) {
SCB_DisableDCache();
}
/* Disable MPU */
ARM_MPU_Disable();
// Document AN12042 'Using the i.MXRT L1 Cache'
// page 5 gives the default configuration, which is overlaid with this one
// where differences exist (i.e. if a region is not specified below,
// it retains it's default configuration)
// ARM_MPU_RASR(DisableExec, AccessPermission, TypeExtField, IsShareable, \
// IsCacheable, IsBufferable, SubRegionDisable, Size)
// 0x80000000-0xDFFFFFFF is external memory like SDRAM etc. Not used.
/* Region 0 setting */ // give external memories no access (1.5Gb total 0x80000000-0xdfffffff)
MPU->RBAR = ARM_MPU_RBAR(0, 0xC0000000U);
MPU->RASR = ARM_MPU_RASR(0, ARM_MPU_AP_NONE, 0, 0, 0, 0, 0, ARM_MPU_REGION_SIZE_512MB);
/* Region 1 setting */ // give external memories no access
MPU->RBAR = ARM_MPU_RBAR(1, 0x80000000U);
MPU->RASR = ARM_MPU_RASR(0, ARM_MPU_AP_NONE, 0, 0, 0, 0, 0, ARM_MPU_REGION_SIZE_1GB);
/* Region 2 setting */
// External flash at 0x60000000-0x7fffffff. Cacheable and executable.
MPU->RBAR = ARM_MPU_RBAR(2, 0x60000000U);
MPU->RASR = ARM_MPU_RASR(0, ARM_MPU_AP_FULL, 0, 0, 1, 1, 0, ARM_MPU_REGION_SIZE_512MB);
/* Region 3 setting */
// This is all of RAM, which we will disable, then make sub-regions with the
// appropriate attributes. 0x00000000-0x3fffffff
MPU->RBAR = ARM_MPU_RBAR(3, 0x00000000U); // default = no access
MPU->RASR = ARM_MPU_RASR(1, ARM_MPU_AP_NONE, 2, 0, 0, 0, 0, ARM_MPU_REGION_SIZE_1GB);
/* Region 4 setting I-TCM */
// 0x00000000-0x0000ffff, Executable, cacheable
MPU->RBAR = ARM_MPU_RBAR(4, 0x00000000U);
MPU->RASR = ARM_MPU_RASR(0, ARM_MPU_AP_FULL, 0, 0, 1, 1, 0, ARM_MPU_REGION_SIZE_64KB);
/* Region 5 setting D-TCM */
// 0x20000000-0x2000ffff, Not executable, cacheable
MPU->RBAR = ARM_MPU_RBAR(5, 0x20000000U);
MPU->RASR = ARM_MPU_RASR(1, ARM_MPU_AP_FULL, 0, 0, 1, 1, 0, ARM_MPU_REGION_SIZE_64KB);
/* Region 6 setting OCRAM */
// 0x20200000-0x2021ffff, Not executable, cacheable
MPU->RBAR = ARM_MPU_RBAR(6, 0x20200000U);
MPU->RASR = ARM_MPU_RASR(1, ARM_MPU_AP_FULL, 0, 0, 1, 1, 0, ARM_MPU_REGION_SIZE_128KB);
/* Enable MPU */
ARM_MPU_Enable(MPU_CTRL_PRIVDEFENA_Msk);
/* Enable I cache and D cache */
SCB_EnableDCache();
SCB_EnableICache();
}
I have no external SDRAM.
I would like somebody who understands the MPU to check for me. For example, ITCM and DTCM do not use the cache, but if I disable the cache in those regions, it does not work!
Many thanks,
Chris.
