Generic Interrupt Controller CPU Interface
ARM DDI 0500D
Copyright © 2013-2014 ARM. All rights reserved.
9-2
ID021414
Non-Confidential
9.1
About the GIC CPU Interface
The GIC CPU Interface, when integrated with a external distributor component, is a resource
for supporting and managing interrupts in a cluster system. It provides:
•
Registers for managing:
—
Interrupt sources.
—
Interrupt behavior.
—
Interrupt routing to one or more cores.
The Cortex-A53 processor implements the GIC CPU interface as described in the Generic
Interrupt Controller (GICv4) architecture. This interfaces with an external GICv3 or GICv4
interrupt distributor component within the system.
The GICv4 architecture supports:
•
Two security states.
•
Interrupt virtualization.
•
Software-generated Interrupts
(SGIs).
•
Message Based Interrupts.
•
System register access.
•
Memory-mapped register access.
•
Interrupt masking and prioritization.
•
Cluster environments, including systems that contain more than eight cores.
•
Wake-up events in power management environments.
The GIC includes interrupt grouping functionality that supports:
•
Signaling interrupt groups to the target core using either the IRQ or the FIQ exception
request, based on software configuration.
•
A unified scheme for handling the priority of Group 0 and Group 1 interrupts.
This chapter describes only features that are specific to the Cortex-A53 processor
implementation.
9.1.1
Bypassing the CPU Interface
The GIC CPU Interface is always implemented within the Cortex-A53 processor. However, you
can disable it if you assert the
GICCDISABLE
signal HIGH at reset. If the GIC is enabled, the
input pins
nVIRQ
and
nVFIQ
must be tied off to HIGH. This is because the internal GIC CPU
interface generates the virtual interrupt signals to the cores. The
nIRQ
and
nFIQ
signals are
controlled by software, therefore there is no requirement to tie them HIGH. If you disable the
GIC CPU interface, the input pins
nVIRQ
and
nVFIQ
can be driven by an external GIC in the
SoC.
Disable the CPU Interface, when the Cortex-A53 processor is not being integrated with an
external GICv3 or GICv4 distributor component in the system, by asserting the
GICCDISABLE
signal HIGH at reset.
Asserting the
GICCDISABLE
signal HIGH at reset removes access to the memory-mapped
and system GIC CPU Interface registers.