PLM remembers the subsystem through the cdo commands during the system boot. When it receives the request for SystemShutdown with subsystem as argument, it releases all the peripheral nodes requested / allocated to the subsystem. If the nodes are not used by any other subsystem, then those nodes are idled and reset as well. PLM reloads the subsystem after pre-allocting (automatic node request) of necessary nodes for the subsystem to start or init. The subsystem itself will request the rest of the nodes when needed.
In case of Linux, the scope for the restart is recorded and remembered by ATF through sysfs entry update. During the Linux reboot call, the ATF issues PmSystemShutdown call to PLM with subsystem as an argument for restart type.
Note: Currently Idling/Reset of the PL peripherals is not supported by PLM. This demo relies on Linux drivers and application to idle the ongoing traffic from PL peripherals.