From: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>

ARM GICv2m specification extends GICv2 to support MSI(-X) with
a new set of register frames. This patch introduces support for
the non-secure GICv2m register frame.

The driver currently matchs "arm,gic-400-plus" in device tree binding,
which implements GICv2m.

The "msi-controller" keyword in ARM GIC devicetree binding is used to indentify
GIC driver that it should enable MSI(-X) support, The region of GICv2m MSI
register frame is specified using the register frame index 4 in the device tree.
MSI support is optional.

Each GIC maintains an "msi_chip" structure. To discover the msi_chip,
PCI host driver can do the following:

    struct device_node *gic_node = of_irq_find_parent(pdev->dev.of_node);
    pcie_bus->msi_chip = of_pci_find_msi_chip_by_node(gic_node);

Cc: Mark Rutland <Mark.Rutland@arm.com>
Cc: Marc Zyngier <redacted>
Cc: Jason Cooper <redacted>
Cc: Catalin Marinas <Catalin.Marinas@arm.com>
Cc: Will Deacon <redacted>
Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
---
 Documentation/devicetree/bindings/arm/gic.txt |  20 +-
 arch/arm64/Kconfig                            |   1 +
 drivers/irqchip/Kconfig                       |   7 +
 drivers/irqchip/Makefile                      |   1 +
 drivers/irqchip/irq-gic-v2m.c                 | 251 ++++++++++++++++++++++++++
 drivers/irqchip/irq-gic-v2m.h                 |  13 ++
 drivers/irqchip/irq-gic.c                     |  23 ++-
 drivers/irqchip/irq-gic.h                     |  31 +++-
 8 files changed, 334 insertions(+), 13 deletions(-)
 create mode 100644 drivers/irqchip/irq-gic-v2m.c
 create mode 100644 drivers/irqchip/irq-gic-v2m.h

diff --git a/Documentation/devicetree/bindings/arm/gic.txt b/Documentation/devicetree/bindings/arm/gic.txt
index 5573c08..d2eea0b 100644
--- a/Documentation/devicetree/bindings/arm/gic.txt
+++ b/Documentation/devicetree/bindings/arm/gic.txt

@@ -12,11 +12,14 @@ Main node required properties:

 - compatible : should be one of:
        "arm,gic-400"
+       "arm,gic-400-v2m"

        "arm,cortex-a15-gic"
        "arm,cortex-a9-gic"
        "arm,cortex-a7-gic"
        "arm,arm11mp-gic"
+
 - interrupt-controller : Identifies the node as an interrupt controller
+
 - #interrupt-cells : Specifies the number of cells needed to encode an
   interrupt source.  The type shall be a <u32> and the value shall be 3.

@@ -37,9 +40,16 @@ Main node required properties:
        the 8 possible cpus attached to the GIC.  A bit set to '1' indicated
        the interrupt is wired to that CPU.  Only valid for PPI interrupts.

-- reg : Specifies base physical address(s) and size of the GIC registers. The
-  first region is the GIC distributor register base and size. The 2nd region is
-  the GIC cpu interface register base and size.
+- reg : Specifies base physical address(s) and size of the GIC register frames.
+
+  Region | Description
+  Index  |
+  -------------------------------------------------------------------
+     0   | GIC distributor register base and size
+     1   | GIC cpu interface register base and size
+     2   | VGIC interface control register base and size (Optional)
+     3   | VGIC CPU interface register base and size (Optional)
+     4   | GICv2m MSI interface register base and size (Optional)