Introduce interrupt registration framework in BL3-1

This patch introduces a framework for registering interrupts routed to
EL3. The interrupt routing model is governed by the SCR_EL3.IRQ and
FIQ bits and the security state an interrupt is generated in. The
framework recognizes three type of interrupts depending upon which
exception level and security state they should be handled in
i.e. Secure EL1 interrupts, Non-secure interrupts and EL3
interrupts. It provides an API and macros that allow a runtime service
to register an handler for a type of interrupt and specify the routing
model. The framework validates the routing model and uses the context
management framework to ensure that it is applied to the SCR_EL3 prior
to entry into the target security state. It saves the handler in
internal data structures. An API is provided to retrieve the handler
when an interrupt of a particular type is asserted. Registration is
expected to be done once by the primary CPU. The same handler and
routing model is used for all CPUs.

Support for EL3 interrupts will be added to the framework in the
future. A makefile flag has been added to allow the FVP port choose
between ARM GIC v2 and v3 support in EL3. The latter version is
currently unsupported.

A framework for handling interrupts in BL3-1 will be introduced in
subsequent patches. The default routing model in the absence of any
handlers expects no interrupts to be routed to EL3.

Change-Id: Idf7c023b34fcd4800a5980f2bef85e4b5c29e649

10 files changed, 422 insertions, 0 deletions

diff --git a/bl31/bl31.mk b/bl31/bl31.mk
index 6c9650f0..93a60c76 100644
--- a/bl31/bl31.mk
+++ b/bl31/bl31.mk
@@ -31,6 +31,7 @@
 BL31_SOURCES		+=	bl31/bl31_main.c				\
 				bl31/context_mgmt.c				\
 				bl31/runtime_svc.c				\
+				bl31/interrupt_mgmt.c				\
 				bl31/aarch64/bl31_arch_setup.c			\
 				bl31/aarch64/bl31_entrypoint.S			\
 				bl31/aarch64/context.S				\
diff --git a/bl31/context_mgmt.c b/bl31/context_mgmt.c
index 41418372..2e7e62d7 100644
--- a/bl31/context_mgmt.c
+++ b/bl31/context_mgmt.c
@@ -35,6 +35,7 @@
 #include <bl31.h>
 #include <context.h>
 #include <context_mgmt.h>
+#include <interrupt_mgmt.h>
 #include <platform.h>
 #include <runtime_svc.h>
 
@@ -160,6 +161,11 @@ void cm_set_el3_eret_context(uint32_t security_state, uint64_t entrypoint,
 	ctx = cm_get_context(read_mpidr(), security_state);
 	assert(ctx);
 
+	/* Program the interrupt routing model for this security state */
+	scr &= ~SCR_FIQ_BIT;
+	scr &= ~SCR_IRQ_BIT;
+	scr |= get_scr_el3_from_routing_model(security_state);
+
 	/* Populate EL3 state so that we've the right context before doing ERET */
 	state = get_el3state_ctx(ctx);
 	write_ctx_reg(state, CTX_SPSR_EL3, spsr);
diff --git a/bl31/interrupt_mgmt.c b/bl31/interrupt_mgmt.c
new file mode 100644
index 00000000..2b0c7970
--- /dev/null
+++ b/bl31/interrupt_mgmt.c
@@ -0,0 +1,206 @@
+/*
+ * Copyright (c) 2014, ARM Limited and Contributors. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer.
+ *
+ * Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ *
+ * Neither the name of ARM nor the names of its contributors may be used
+ * to endorse or promote products derived from this software without specific
+ * prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <assert.h>
+#include <bl_common.h>
+#include <context_mgmt.h>
+#include <errno.h>
+#include <interrupt_mgmt.h>
+#include <platform.h>
+#include <stdio.h>
+
+/*******************************************************************************
+ * Local structure and corresponding array to keep track of the state of the
+ * registered interrupt handlers for each interrupt type.
+ * The field descriptions are:
+ *
+ * 'flags' : Bit[0], Routing model for this interrupt type when execution is
+ *                   not in EL3 in the secure state. '1' implies that this
+ *                   interrupt will be routed to EL3. '0' implies that this
+ *                   interrupt will be routed to the current exception level.
+ *
+ *           Bit[1], Routing model for this interrupt type when execution is
+ *                   not in EL3 in the non-secure state. '1' implies that this
+ *                   interrupt will be routed to EL3. '0' implies that this
+ *                   interrupt will be routed to the current exception level.
+ *
+ *           All other bits are reserved and SBZ.
+ *
+ * 'scr_el3[2]'  : Mapping of the routing model in the 'flags' field to the
+ *                 value of the SCR_EL3.IRQ or FIQ bit for each security state.
+ *                 There are two instances of this field corresponding to the
+ *                 two security states.
+ ******************************************************************************/
+typedef struct intr_type_desc {
+	interrupt_type_handler_t handler;
+	uint32_t flags;
+	uint32_t scr_el3[2];
+} intr_type_desc_t;
+
+static intr_type_desc_t intr_type_descs[MAX_INTR_TYPES];
+
+/*******************************************************************************
+ * This function validates the interrupt type. EL3 interrupts are currently not
+ * supported.
+ ******************************************************************************/
+static int32_t validate_interrupt_type(uint32_t type)
+{
+	if (type == INTR_TYPE_EL3)
+		return -ENOTSUP;
+
+	if (type != INTR_TYPE_S_EL1 && type != INTR_TYPE_NS)
+		return -EINVAL;
+
+	return 0;
+}
+
+/*******************************************************************************
+* This function validates the routing model for this type of interrupt
+ ******************************************************************************/
+static int32_t validate_routing_model(uint32_t type, uint32_t flags)
+{
+	flags >>= INTR_RM_FLAGS_SHIFT;
+	flags &= INTR_RM_FLAGS_MASK;
+
+	if (type == INTR_TYPE_S_EL1)
+		return validate_sel1_interrupt_rm(flags);
+
+	if (type == INTR_TYPE_NS)
+		return validate_ns_interrupt_rm(flags);
+
+	return -EINVAL;
+}
+
+/*******************************************************************************
+ * This function returns the cached copy of the SCR_EL3 which contains the
+ * routing model (expressed through the IRQ and FIQ bits) for a security state
+ * which was stored through a call to 'set_routing_model()' earlier.
+ ******************************************************************************/
+uint32_t get_scr_el3_from_routing_model(uint32_t security_state)
+{
+	uint32_t scr_el3;
+
+	assert(security_state <= NON_SECURE);
+	scr_el3 = intr_type_descs[INTR_TYPE_NS].scr_el3[security_state];
+	scr_el3 |= intr_type_descs[INTR_TYPE_S_EL1].scr_el3[security_state];
+	scr_el3 |= intr_type_descs[INTR_TYPE_EL3].scr_el3[security_state];
+	return scr_el3;
+}
+
+/*******************************************************************************
+ * This function uses the 'interrupt_type_flags' parameter to obtain the value
+ * of the trap bit (IRQ/FIQ) in the SCR_EL3 for a security state for this
+ * interrupt type. It uses it to update the SCR_EL3 in the cpu context and the
+ * 'intr_type_desc' for that security state.
+ ******************************************************************************/
+static void set_scr_el3_from_rm(uint32_t type,
+				uint32_t interrupt_type_flags,
+				uint32_t security_state)
+{
+	uint32_t flag, bit_pos;
+
+	flag = get_interrupt_rm_flag(interrupt_type_flags, security_state);
+	bit_pos = plat_interrupt_type_to_line(type, security_state);
+	intr_type_descs[type].scr_el3[security_state] = flag << bit_pos;
+	cm_write_scr_el3_bit(security_state, bit_pos, flag);
+}
+
+/*******************************************************************************
+ * This function validates the routing model specified in the 'flags' and
+ * updates internal data structures to reflect the new routing model. It also
+ * updates the copy of SCR_EL3 for each security state with the new routing
+ * model in the 'cpu_context' structure for this cpu.
+ ******************************************************************************/
+int32_t set_routing_model(uint32_t type, uint32_t flags)
+{
+	int32_t rc;
+
+	rc = validate_interrupt_type(type);
+	if (rc)
+		return rc;
+
+	rc = validate_routing_model(type, flags);
+	if (rc)
+		return rc;
+
+	/* Update the routing model in internal data structures */
+	intr_type_descs[type].flags = flags;
+	set_scr_el3_from_rm(type, flags, SECURE);
+	set_scr_el3_from_rm(type, flags, NON_SECURE);
+
+	return 0;
+}
+
+/*******************************************************************************
+ * This function registers a handler for the 'type' of interrupt specified. It
+ * also validates the routing model specified in the 'flags' for this type of
+ * interrupt.
+ ******************************************************************************/
+int32_t register_interrupt_type_handler(uint32_t type,
+					interrupt_type_handler_t handler,
+					uint32_t flags)
+{
+	int32_t rc;
+
+	/* Validate the 'handler' parameter */
+	if (!handler)
+		return -EINVAL;
+
+	/* Validate the 'flags' parameter */
+	if (flags & INTR_TYPE_FLAGS_MASK)
+		return -EINVAL;
+
+	/* Check if a handler has already been registered */
+	if (intr_type_descs[type].handler)
+		return -EALREADY;
+
+	rc = set_routing_model(type, flags);
+	if (rc)
+		return rc;
+
+	/* Save the handler */
+	intr_type_descs[type].handler = handler;
+
+	return 0;
+}
+
+/*******************************************************************************
+ * This function is called when an interrupt is generated and returns the
+ * handler for the interrupt type (if registered). It returns NULL if the
+ * interrupt type is not supported or its handler has not been registered.
+ ******************************************************************************/
+interrupt_type_handler_t get_interrupt_type_handler(uint32_t type)
+{
+	if (validate_interrupt_type(type))
+		return NULL;
+
+	return intr_type_descs[type].handler;
+}
+
diff --git a/docs/user-guide.md b/docs/user-guide.md
index e7f0df54..201db384 100644
--- a/docs/user-guide.md
+++ b/docs/user-guide.md
@@ -157,6 +157,10 @@ performed.
 *   `V`: Verbose build. If assigned anything other than 0, the build commands
     are printed. Default is 0
 
+*   `FVP_GIC_ARCH`: Choice of ARM GIC architecture version used by the FVP port
+    for implementing the platform GIC API. This API is used by the interrupt
+    management framework. Default is 2 i.e. version 2.0
+
 ### Creating a Firmware Image Package
 
 FIPs are automatically created as part of the build instructions described in
diff --git a/drivers/arm/gic/gic_v2.c b/drivers/arm/gic/gic_v2.c
index 00464cbd..27a39b9c 100644
--- a/drivers/arm/gic/gic_v2.c
+++ b/drivers/arm/gic/gic_v2.c
@@ -28,8 +28,10 @@
  * POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include <arch.h>
 #include <assert.h>
 #include <gic_v2.h>
+#include <interrupt_mgmt.h>
 #include <mmio.h>
 
 /*******************************************************************************
@@ -290,3 +292,27 @@ void gicd_set_itargetsr(unsigned int base, unsigned int id, unsigned int iface)
 			     (1 << iface) << (byte_off << 3));
 }
 
+/*******************************************************************************
+ * This function allows the interrupt management framework to determine (through
+ * the platform) which interrupt line (IRQ/FIQ) to use for an interrupt type to
+ * route it to EL3. The interrupt line is represented as the bit position of the
+ * IRQ or FIQ bit in the SCR_EL3.
+ ******************************************************************************/
+uint32_t gicv2_interrupt_type_to_line(uint32_t cpuif_base, uint32_t type)
+{
+	uint32_t gicc_ctlr;
+
+	/* Non-secure interrupts are signalled on the IRQ line always */
+	if (type == INTR_TYPE_NS)
+		return __builtin_ctz(SCR_IRQ_BIT);
+
+	/*
+	 * Secure interrupts are signalled using the IRQ line if the FIQ_EN
+	 * bit is not set else they are signalled using the FIQ line.
+	 */
+	gicc_ctlr = gicc_read_ctlr(cpuif_base);
+	if (gicc_ctlr & FIQ_EN)
+		return __builtin_ctz(SCR_FIQ_BIT);
+	else
+		return __builtin_ctz(SCR_IRQ_BIT);
+}
diff --git a/include/bl31/interrupt_mgmt.h b/include/bl31/interrupt_mgmt.h
new file mode 100644
index 00000000..0b24f39a
--- /dev/null
+++ b/include/bl31/interrupt_mgmt.h
@@ -0,0 +1,128 @@
+/*
+ * Copyright (c) 2014, ARM Limited and Contributors. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer.
+ *
+ * Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ *
+ * Neither the name of ARM nor the names of its contributors may be used
+ * to endorse or promote products derived from this software without specific
+ * prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef __INTERRUPT_MGMT_H__
+#define __INTERRUPT_MGMT_H__
+
+#include <arch.h>
+
+/*******************************************************************************
+ * Constants for the types of interrupts recognised by the IM framework
+ ******************************************************************************/
+#define INTR_TYPE_S_EL1			0
+#define INTR_TYPE_EL3			1
+#define INTR_TYPE_NS			2
+#define MAX_INTR_TYPES			3
+#define INTR_TYPE_INVAL			MAX_INTR_TYPES
+/*
+ * Constant passed to the interrupt handler in the 'id' field when the
+ * framework does not read the gic registers to determine the interrupt id.
+ */
+#define INTR_ID_UNAVAILABLE		0xFFFFFFFF
+
+
+/*******************************************************************************
+ * Mask for _both_ the routing model bits in the 'flags' parameter and
+ * constants to define the valid routing models for each supported interrupt
+ * type
+ ******************************************************************************/
+#define INTR_RM_FLAGS_SHIFT		0x0
+#define INTR_RM_FLAGS_MASK		0x3
+/* Routed to EL3 from NS. Taken to S-EL1 from Secure */
+#define INTR_SEL1_VALID_RM0		0x2
+/* Routed to EL3 from NS and Secure */
+#define INTR_SEL1_VALID_RM1		0x3
+/* Routed to EL1/EL2 from NS and to S-EL1 from Secure */
+#define INTR_NS_VALID_RM0		0x0
+/* Routed to EL1/EL2 from NS and to EL3 from Secure */
+#define INTR_NS_VALID_RM1		0x1
+
+
+/*******************************************************************************
+ * Constants for the _individual_ routing model bits in the 'flags' field for
+ * each interrupt type and mask to validate the 'flags' parameter while
+ * registering an interrupt handler
+ ******************************************************************************/
+#define INTR_TYPE_FLAGS_MASK		0xFFFFFFFC
+
+#define INTR_RM_FROM_SEC_SHIFT		SECURE		/* BIT[0] */
+#define INTR_RM_FROM_NS_SHIFT		NON_SECURE	/* BIT[1] */
+#define INTR_RM_FROM_FLAG_MASK		1
+#define get_interrupt_rm_flag(flag, ss)	(((flag >> INTR_RM_FLAGS_SHIFT) >> ss) \
+					 & INTR_RM_FROM_FLAG_MASK)
+#define set_interrupt_rm_flag(flag, ss)	(flag |= 1 << ss)
+#define clr_interrupt_rm_flag(flag, ss)	(flag &= ~(1 << ss))
+
+
+/*******************************************************************************
+ * Macros to validate the routing model bits in the 'flags' for a type
+ * of interrupt. If the model does not match one of the valid masks
+ * -EINVAL is returned.
+ ******************************************************************************/
+#define validate_sel1_interrupt_rm(x)	(x == INTR_SEL1_VALID_RM0 ? 0 : \
+					 (x == INTR_SEL1_VALID_RM1 ? 0 :\
+					  -EINVAL))
+
+#define validate_ns_interrupt_rm(x)	(x == INTR_NS_VALID_RM0 ? 0 : \
+					 (x == INTR_NS_VALID_RM1 ? 0 :\
+					  -EINVAL))
+
+/*******************************************************************************
+ * Macros to set the 'flags' parameter passed to an interrupt type handler. Only
+ * the flag to indicate the security state when the exception was generated is
+ * supported.
+ ******************************************************************************/
+#define INTR_SRC_SS_FLAG_SHIFT		0		/* BIT[0] */
+#define INTR_SRC_SS_FLAG_MASK		1
+#define set_interrupt_src_ss(flag, val)	(flag |= val << INTR_SRC_SS_FLAG_SHIFT)
+#define clr_interrupt_src_ss(flag)	(flag &= ~(1 << INTR_SRC_SS_FLAG_SHIFT))
+#define get_interrupt_src_ss(flag)	((flag >> INTR_SRC_SS_FLAG_SHIFT) & \
+					 INTR_SRC_SS_FLAG_MASK)
+
+#ifndef __ASSEMBLY__
+
+/* Prototype for defining a handler for an interrupt type */
+typedef uint64_t (*interrupt_type_handler_t)(uint32_t id,
+					     uint32_t flags,
+					     void *handle,
+					     void *cookie);
+
+/*******************************************************************************
+ * Function & variable prototypes
+ ******************************************************************************/
+extern uint32_t get_scr_el3_from_routing_model(uint32_t security_state);
+extern int32_t set_routing_model(uint32_t type, uint32_t flags);
+extern int32_t register_interrupt_type_handler(uint32_t type,
+					       interrupt_type_handler_t handler,
+					       uint32_t flags);
+extern interrupt_type_handler_t get_interrupt_type_handler(uint32_t interrupt_type);
+
+#endif /*__ASSEMBLY__*/
+#endif /* __INTERRUPT_MGMT_H__ */
diff --git a/include/drivers/arm/gic_v2.h b/include/drivers/arm/gic_v2.h
index ccf3d32c..91c3f11e 100644
--- a/include/drivers/arm/gic_v2.h
+++ b/include/drivers/arm/gic_v2.h
@@ -298,6 +298,12 @@ static inline void gicc_write_dir(unsigned int base, unsigned int val)
 	mmio_write_32(base + GICC_DIR, val);
 }
 
+/*******************************************************************************
+ * Prototype of function to map an interrupt type to the interrupt line used to
+ * signal it.
+ ******************************************************************************/
+uint32_t gicv2_interrupt_type_to_line(uint32_t cpuif_base, uint32_t type);
+
 #endif /*__ASSEMBLY__*/
 
 #endif /* __GIC_V2_H__ */
diff --git a/plat/fvp/plat_gic.c b/plat/fvp/plat_gic.c
index db3c9cf6..dd409f56 100644
--- a/plat/fvp/plat_gic.c
+++ b/plat/fvp/plat_gic.c
@@ -29,9 +29,12 @@
  */
 
 #include <arch_helpers.h>
+#include <assert.h>
+#include <bl_common.h>
 #include <debug.h>
 #include <gic_v2.h>
 #include <gic_v3.h>
+#include <interrupt_mgmt.h>
 #include <platform.h>
 #include <stdint.h>
 
@@ -284,3 +287,38 @@ void gic_setup(void)
 	gic_cpuif_setup(gicc_base);
 	gic_distif_setup(gicd_base);
 }
+
+/*******************************************************************************
+ * An ARM processor signals interrupt exceptions through the IRQ and FIQ pins.
+ * The interrupt controller knows which pin/line it uses to signal a type of
+ * interrupt. The platform knows which interrupt controller type is being used
+ * in a particular security state e.g. with an ARM GIC, normal world could use
+ * the GICv2 features while the secure world could use GICv3 features and vice
+ * versa.
+ * This function is exported by the platform to let the interrupt management
+ * framework determine for a type of interrupt and security state, which line
+ * should be used in the SCR_EL3 to control its routing to EL3. The interrupt
+ * line is represented as the bit position of the IRQ or FIQ bit in the SCR_EL3.
+ ******************************************************************************/
+uint32_t plat_interrupt_type_to_line(uint32_t type, uint32_t security_state)
+{
+	uint32_t gicc_base = platform_get_cfgvar(CONFIG_GICC_ADDR);
+
+	assert(type == INTR_TYPE_S_EL1 ||
+	       type == INTR_TYPE_EL3 ||
+	       type == INTR_TYPE_NS);
+
+	assert(security_state == NON_SECURE || security_state == SECURE);
+
+	/*
+	 * We ignore the security state parameter under the assumption that
+	 * both normal and secure worlds are using ARM GICv2. This parameter
+	 * will be used when the secure world starts using GICv3.
+	 */
+#if FVP_GIC_ARCH == 2
+	return gicv2_interrupt_type_to_line(gicc_base, type);
+#else
+#error "Invalid GIC architecture version specified for FVP port"
+#endif
+}
+
diff --git a/plat/fvp/platform.h b/plat/fvp/platform.h
index bd76d678..814fb776 100644
--- a/plat/fvp/platform.h
+++ b/plat/fvp/platform.h
@@ -430,6 +430,8 @@ extern void gic_cpuif_deactivate(unsigned int);
 extern void gic_cpuif_setup(unsigned int);
 extern void gic_pcpu_distif_setup(unsigned int);
 extern void gic_setup(void);
+extern uint32_t plat_interrupt_type_to_line(uint32_t type,
+					    uint32_t security_state);
 
 /* Declarations for fvp_topology.c */
 extern int plat_setup_topology(void);
diff --git a/plat/fvp/platform.mk b/plat/fvp/platform.mk
index 4de001bc..3ae36d83 100644
--- a/plat/fvp/platform.mk
+++ b/plat/fvp/platform.mk
@@ -71,3 +71,8 @@ ifeq (${RESET_TO_BL31}, 1)
 	BL31_SOURCES		+=	drivers/arm/tzc400/tzc400.c		\
 					plat/fvp/plat_security.c
 endif
+
+# Flag used by the FVP port to determine the version of ARM GIC architecture
+# to use for interrupt management in EL3.
+FVP_GIC_ARCH		:=	2
+$(eval $(call add_define,FVP_GIC_ARCH))