AM263P4-Q1: fail to boot multi-core image in customer bootloader

Tool/software:

Hi, experts,

I raise this question for my customer as he has some problem in initializing new thread.

The expected boot flow is RBL -> SBL -> PBL(customer's bootloader) -> APP. Below are tests we have done and the corresponding results. Please help to analyze and guide the way to implement expected boot flow with AM263P. Thanks.

1. Core-0, Core-2 and Core-3 are used in the application.
2. This boot flow works well in customer's previous projects with AM2634.
3. The multi-core image can be booted by SBL correctly.
4. Single-core image (application for Core-0) can be booted by PBL correctly.
5. If booting multi-core image by PBL, it is stuck in loading image of Core-3. And
   1. Core-3 and Core-1 is unconnectable by XDS110, but it is already set to dual-core/STANDALONE mode in SBL.
   2. ATCM of Core-3 is not accessible, "????????" displayed in memory browser.
6. Same MPU setting with previous AM2634 projects. 

SDK Version: 10.1.0.31