Hello !
I try to study usage of K82 MPU for FreeRTOS like OS.
I can see in original FreeRTOS MPU few places where all 4 regions of generic ARM MPU is updated on fly.
Prepared valued are copied directly to MPU registers.
/* ARM generic */
" ldr r2, =0xe000ed9c \n" /* Region Base Address register. */
" ldmia r1!, {r4-r11} \n" /* Read 4 sets of MPU registers. */
" stmia r2!, {r4-r11} \n" /* Write 4 sets of MPU registers. */
In K82 case, one region is represented by 4 dwords and prepared MPU region values from TCB ( for 4 regions ) can
be copied by operations like this :
/* K82 */
" ldr r2, =0x4000D410 \n" /* Region Base Address register. */ // 1,2
" ldmia r1!, {r4-r11} \n" /* Read 2 sets of MPU registers. */
" stmia r2!, {r4-r11} \n" /* Write 2 sets of MPU registers. */
" ldr r2, =0x4000D430 \n" /* Region Base Address register. */ // 3,4
" ldmia r1!, {r4-r11} \n" /* Read 2 sets of MPU registers. */
" stmia r2!, {r4-r11} \n" /* Write 2 sets of MPU registers. */
In case of ARM, priviliged/nonprivileged mode is switched in control register.
But what in case of K82 ?
How I can update MPU region entries during runtime ?
Should I also disable MPU or current way of FreeRTOS is sufficient for K82 as well ?
I can see the next MPU region scheme :
Region 0 is reserved for debug purposes and should be invalidated when it is no need.
Regions 1-4 are preconfigured one time for protect static flash/data regions
Regions 5-8 are updated during runtime when task switch happens.
Regions 9-12 are invalidated at start up and set to 0.
So MPU is always enabled.
How-to properly and in what mode update regions 5-8 ?
Thank you !
Eugene
