Requesting and Releasing Slave Nodes - 2022.1 English

Versal ACAP System Software Developers Guide (UG1304)

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2022.1 English

When a processing unit requires a peripheral or memory slave node, it must request the slave node using the power management API. After the slave node has performed its function and is no longer required, it can be released and powered off.

The following figure shows the call flow for a use case where the APU and the RPU are sharing an on-chip memory bank, ocm0.

Figure 1. Platform Management Framework Call Sequence for APU and RPU Sharing an On-Chip Memory Bank
Note: The ocm0 memory remains powered on after the APU calls XStatus XPm_ReleaseNode, because the RPU has also requested the same slave node. After the RPU also releases the ocm0 node, then the PMC requests the PSM to power off the ocm0 memory.
Note: Even though individual TCMs (TCM0A, TCM0B, TCM1A, TCM1B) can be requested/released individually, the platform management firmware will power up/down both TCMs (TCMA/TCMB) synchronously. This means both the TCMs will be powered down together when both the TCMs are unused. Similarly, both the TCMs will be powered up, even though one TCM is requested. This is done to handle power dependencies between both the TCMs.