SPMU447 June 2026 CC2755P20
The DMA firewall is a concatenation of two back-to-back firewalls. The first stage is explained below, and the second stage is the same as the master TrustZone⢠in the system and controlled by TCM.
DMA is performing a secure transaction for the secure mailbox task:
All addresses are accessible.
DMA performing non-secure transaction for non-secure mailbox task:
Non-secure accesses are allowed; that is, access to the address space with bit 28 set to '1'.
Secure accesses are blocked; that is, access to the address space with bit 28 set to '0'.
Blocked transactions will internally cause a DMA transaction error. This firewall can be enabled/disabled through CTL.DMAFWDIS.