When a processing unit requires a peripheral or memory node, it must request it using the power management API. After the peripheral 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 peripheral
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.