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Can't understand the configuration of MPC on M33

ziming over 4 years ago

I can use some help in understanding how to configure MPC for M33. I uses an MPS2+ board with AN505 (IOTKit_CM33). I run the example TrustZone code which is available from uVision Pack installer.

Background: the device AN505 has SSRAM1 (4MB) and SSRAM3 (2MB). SSRAM1 is mapped at 1) 0x0000_0000 - 0x003F_FFFF (NS) 2) 0x0040_0000 - 0x007F_FFFF (NS) 3) 0x1000_0000 - 0x103F_FFFF (S) and 4) 0x1040_0000 - 0x107F_FFFF (S). SSRAM3 is mapped at 1) 0x2820_0000 - 0x283F_FFFF (NS) and 2) 0x3820_0000 - 0x383F_FFFF (S). SSRAM1 has a MPC block size of 128KB. SSRAM3 has a block size of 64KB.

We are configuring half of SSRAM1 to normal world and the whole SSRAM3 to normal world.

The example code shows

/* configure unsecure code area MPSSSRAM1 (0x00200000 - 0x003FFFFF) */
  //  blk_max = IOTKIT_MPCSSRAM1->BLK_MAX;   /* = 0x1     */
  //  blk_cfg = IOTKIT_MPCSSRAM1->BLK_CFG;   /* = 0xC     */
  //  blk_size = 1UL << (blk_cfg + 5U);      /* = 0x20000 = 128 kB, 4MB / 128kB = 32 bit*/
  //  blk_cnt  = 0x200000U / blk_size;       /* = 0x10    */

  IOTKIT_MPCSSRAM1->CTRL &= ~(1UL << 8U);   /* clear auto increment */
  IOTKIT_MPCSSRAM1->BLK_IDX = 0;            /* write LUT index */
  IOTKIT_MPCSSRAM1->BLK_LUT = 0xFFFF0000UL; /* configure blocks.  0x00200000-0x003fffff: non-secure; 0x00000-0x1ffff: secure, alias to 0x10000000-0x101fffff*/

  /* configure unsecure data area MPSSSRAM3 (0x28200000 - 0x283FFFFF) */
  //  blk_max = IOTKIT_MPCSSRAM3->BLK_MAX;   /* = 0x1     */
  //  blk_cfg = IOTKIT_MPCSSRAM3->BLK_CFG;   /* = 0xB     */
  //  blk_size = 1UL << (blk_cfg + 5U);      /* = 0x10000 = 64 kB, 2MB / 64 kB = 32 bit */
  //  blk_cnt  = 0x200000U / blk_size;       /* = 0x20    */

  IOTKIT_MPCSSRAM3->CTRL &= ~(1UL << 8U);   /* clear auto increment */
  IOTKIT_MPCSSRAM3->BLK_IDX = 1;            /* write LUT index */
  IOTKIT_MPCSSRAM3->BLK_LUT = 0xFFFFFFFFUL; /* configure blocks */

This does not make sense to me:

1) SSRAM3 is 2MB. It should have 2048KB/64KB = 32 blocks. So, we should only need 1 BLK_LUT. So, we should set BLK_IDX = 0. But the code set BLK_IDX to 1.

2) In the comment of setting SSRAM1, it says "blk_cnt = 0x10". Is this an error? Shouldn't it be 0x400000/blk_size = 0x20. SInce it is just comment, I guess it does not matter anyway.

I am quite confused here. Thank you in advance for the clarification.