|Home > Operation > Multichip operation > Isolating a chip from the system|
You can isolate a chip from the system.
To isolate a chip from the system, use the following procedure:
Attempt to enter the CONFIG state (pstate =
If the GIC is idle and all credits are returned, it accepts the request to go into CONFIG state, otherwise it denies the request and remains in RUN state.
When in the CONFIG state, any cross-chip messages that change the internal state are held in the cross-chip interface, and all messages assert pactive. If pactive asserts while attempting to enter a lower power state, you must return to RUN (pstate ==
If required, flush the LPI cache using GICR_WAKER.Sleep.
Arm recommends that if wake-on-interrupt is required, LPIs from other chips do not target this chip while the chip is being powered down (step 3), and must be routed back while the chip is in the OFF state.
LPIs that arrive after sleep is set in the CONFIG state are dropped.
Attempt to enter the OFF state.
Use the Q-Channel to put the GIC into a safe mode to reset.
Power up is the reverse of the powerdown sequence. However, you must ensure that the Routing table is restored before other registers, else the behavior is unpredictable. Restoring values to the Routing table that are not exactly the same as those read out before a reset, can cause unpredictable behavior.