SPRUIE9D May 2017 – May 2024 DRA74P , DRA75P , DRA76P , DRA77P
There are some inputs at the MPU core (MPU_Cx) boundary which can be tied off to disable certain kind of transactions appearing on the AMBA4 interface:
For detailed description on these inputs, see the Arm Cortex-A15 Technical Reference Manual (available at infocenter.arm.com/help/index.jsp).
To give flexibility and mitigate risk, a programmable register (AMBA_IF_MODE) is added to control the tie-off value of these MPU_Cx inputs. Once this register is programmed, MPU power domain has to go through OSWRET transition for the programmed values in bits AMBA_IF_MODE [3:0] to take effect. This is because the MPU_Cx non-cpu logic latches the value on the corresponding inputs when it is coming out of reset.
These are the only legal combinations of [BI, BO, BCM, SBD] allowed:
The ROM code provides specific API for configuring the AMBA_IF_MODE register. For more information, see section Wakeup Generator, in Chapter 34, Initialization.