SPRUIM2H May 2020 – October 2023 AM2431 , AM2432 , AM2434 , AM6411 , AM6412 , AM6421 , AM6422 , AM6441 , AM6442
The SoC has limited IO Coherency support through the ACP interface of the MPU Cluster. Sending transactions to the ACP interface allows those transactions, outside of the MPU cluster, to directly go through the shared L2 cache controller. There are two types of cache operations supported through ACP: write allocation and write through. Read through ACP interface has no impact on the cache operation. The main function of the ACP interface is to allow write transactions from the SoC side to push data directly into the MPU's L2 cache. Therefore, the MPU can access this data much faster from the L2 cache rather than fetching it from system memory, while sill maintaining the cache coherency.
Not all initiators have the capability to send transactions to ACP interface for IO coherency. This feature is limited to a subset of the initiators such as BCDMA, pktDMA, and some high-speed peripherals such as USB and EMMC. The transactions sent to the ACP interface must have the ASEL value set to either 14 or 15.
By default, all transactions have ASEL set to zero. For any transactions from pktDMA and BCDMA, the ASEL can be set as part of the DMA configuration. For all other transactions, the ASEL value can be set through QoS MMR. For more details, see Quality of Service (QoS) Block.
Not all initiators have a connection to the ACP interface. MPU A53SS, DebugSS and Security Manager do not have access to ACP interfaces even with the ASEL value set to 14 or 15.