GIC: Add APIs to set interrupt type and query support

The back end GIC driver converts and assigns the interrupt type to
suitable group.

For GICv2, a build option GICV2_G0_FOR_EL3 is introduced, which
determines to which type Group 0 interrupts maps to.

 - When the build option is set 0 (the default), Group 0 interrupts are
   meant for Secure EL1. This is presently the case.

 - Otherwise, Group 0 interrupts are meant for EL3. This means the SPD
   will have to synchronously hand over the interrupt to Secure EL1.

The query API allows the platform to query whether the platform supports
interrupts of a given type.

API documentation updated.

Change-Id: I60fdb4053ffe0bd006b3b20914914ebd311fc858
Co-authored-by: Yousuf A <yousuf.sait@arm.com>
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>

2 files changed, 87 insertions, 0 deletions

diff --git a/docs/platform-interrupt-controller-API.rst b/docs/platform-interrupt-controller-API.rst
index 3161c20a2..3d46cf344 100644
--- a/docs/platform-interrupt-controller-API.rst
+++ b/docs/platform-interrupt-controller-API.rst
@@ -126,6 +126,80 @@ This API should set the priority of the interrupt specified by first parameter
 In case of ARM standard platforms using GIC, the implementation of the API
 writes to GIC *Priority Register* set interrupt priority.
 
+Function: int plat_ic_has_interrupt_type(unsigned int type); [optional]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+::
+
+    Argument : unsigned int
+    Return   : int
+
+This API should return whether the platform supports a given interrupt type. The
+parameter ``type`` shall be one of ``INTR_TYPE_EL3``, ``INTR_TYPE_S_EL1``, or
+``INTR_TYPE_NS``.
+
+In case of ARM standard platforms using GICv3, the implementation of the API
+returns ``1`` for all interrupt types.
+
+In case of ARM standard platforms using GICv2, the API always return ``1`` for
+``INTR_TYPE_NS``. Return value for other types depends on the value of build
+option ``GICV2_G0_FOR_EL3``:
+
+- For interrupt type ``INTR_TYPE_EL3``:
+
+  - When ``GICV2_G0_FOR_EL3`` is ``0``, it returns ``0``, indicating no support
+    for EL3 interrupts.
+
+  - When ``GICV2_G0_FOR_EL3`` is ``1``, it returns ``1``, indicating support for
+    EL3 interrupts.
+
+- For interrupt type ``INTR_TYPE_S_EL1``:
+
+  - When ``GICV2_G0_FOR_EL3`` is ``0``, it returns ``1``, indicating support for
+    Secure EL1 interrupts.
+
+  - When ``GICV2_G0_FOR_EL3`` is ``1``, it returns ``0``, indicating no support
+    for Secure EL1 interrupts.
+
+Function: void plat_ic_set_interrupt_type(unsigned int id, unsigned int type); [optional]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+::
+
+    Argument : unsigned int
+    Argument : unsigned int
+    Return   : void
+
+This API should set the interrupt specified by first parameter ``id`` to the
+type specified by second parameter ``type``. The ``type`` parameter can be
+one of:
+
+- ``INTR_TYPE_NS``: interrupt is meant to be consumed by the Non-secure world.
+
+- ``INTR_TYPE_S_EL1``: interrupt is meant to be consumed by Secure EL1.
+
+- ``INTR_TYPE_EL3``: interrupt is meant to be consumed by EL3.
+
+In case of ARM standard platforms using GIC, the implementation of the API
+writes to the GIC *Group Register* and *Group Modifier Register* (only GICv3) to
+assign the interrupt to the right group.
+
+For GICv3:
+
+- ``INTR_TYPE_NS`` maps to Group 1 interrupt.
+
+- ``INTR_TYPE_S_EL1`` maps to Secure Group 1 interrupt.
+
+- ``INTR_TYPE_EL3`` maps to Secure Group 0 interrupt.
+
+For GICv2:
+
+- ``INTR_TYPE_NS`` maps to Group 1 interrupt.
+
+- When the build option ``GICV2_G0_FOR_EL3`` is set to ``0`` (the default),
+  ``INTR_TYPE_S_EL1`` maps to Group 0. Otherwise, ``INTR_TYPE_EL3`` maps to
+  Group 0 interrupt.
+
 ----
 
 *Copyright (c) 2017, ARM Limited and Contributors. All rights reserved.*
diff --git a/docs/user-guide.rst b/docs/user-guide.rst
index 67af42562..80273be2b 100644
--- a/docs/user-guide.rst
+++ b/docs/user-guide.rst
@@ -386,6 +386,19 @@ Common build options
    images will include support for Trusted Board Boot, but the FIP and FWU\_FIP
    will not include the corresponding certificates, causing a boot failure.
 
+-  ``GICV2_G0_FOR_EL3``: Unlike GICv3, the GICv2 architecture doesn't have
+   inherent support for specific EL3 type interrupts. Setting this build option
+   to ``1`` assumes GICv2 *Group 0* interrupts are expected to target EL3, both
+   by `platform abstraction layer`__ and `Interrupt Management Framework`__.
+   This allows GICv2 platforms to enable features requiring EL3 interrupt type.
+   This also means that all GICv2 Group 0 interrupts are delivered to EL3, and
+   the Secure Payload interrupts needs to be synchronously handed over to Secure
+   EL1 for handling. The default value of this option is ``0``, which means the
+   Group 0 interrupts are assumed to be handled by Secure EL1.
+
+   .. __: `platform-interrupt-controller-API.rst`
+   .. __: `interrupt-framework-design.rst`
+
 -  ``HANDLE_EA_EL3_FIRST``: When defined External Aborts and SError Interrupts
    will be always trapped in EL3 i.e. in BL31 at runtime.