bl32: add secure interrupt handling in AArch32 sp_min

Add support for a minimal secure interrupt service in sp_min for
the AArch32 implementation. Hard code that only FIQs are handled.

Introduce bolean build directive SP_MIN_WITH_SECURE_FIQ to enable
FIQ handling from SP_MIN.

Configure SCR[FIQ] and SCR[FW] from generic code for both cold and
warm boots to handle FIQ in secure state from monitor.

Since SP_MIN architecture, FIQ are always trapped when system executes
in non secure state. Hence discard relay of the secure/non-secure
state in the FIQ handler.

Change-Id: I1f7d1dc7b21f6f90011b7f3fcd921e455592f5e7
Signed-off-by: Etienne Carriere <etienne.carriere@st.com>
diff --git a/bl32/sp_min/sp_min_main.c b/bl32/sp_min/sp_min_main.c
index 1c83cbe..06b0f33 100644
--- a/bl32/sp_min/sp_min_main.c
+++ b/bl32/sp_min/sp_min_main.c
@@ -207,3 +207,19 @@
 	copy_cpu_ctx_to_smc_stx(get_regs_ctx(cm_get_context(NON_SECURE)),
 			next_smc_ctx);
 }
+
+#if SP_MIN_WITH_SECURE_FIQ
+/******************************************************************************
+ * This function is invoked on secure interrupts. By construction of the
+ * SP_MIN, secure interrupts can only be handled when core executes in non
+ * secure state.
+ *****************************************************************************/
+void sp_min_fiq(void)
+{
+	uint32_t id;
+
+	id = plat_ic_acknowledge_interrupt();
+	sp_min_plat_fiq_handler(id);
+	plat_ic_end_of_interrupt(id);
+}
+#endif /* SP_MIN_WITH_SECURE_FIQ */