ACPI / processor: Make it possible to get APIC ID via GIC

Introduce a new function map_gic_id() to allow APIC IDs to be obtained
from the GIC Structure introduced by ACPI 5.
Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
[rjw: Subject and changelog]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/processor_core.c

@@ -71,6 +71,28 @@ static int map_lsapic_id(struct acpi_subtable_header *entry,
 	return 0;
 }
 
+static int map_gic_id(struct acpi_subtable_header *entry,
+		int device_declaration, u32 acpi_id, int *apic_id)
+{
+	struct acpi_madt_generic_interrupt *gic =
+		(struct acpi_madt_generic_interrupt *)entry;
+
+	if (!(gic->flags & ACPI_MADT_ENABLED))
+		return -ENODEV;
+
+	/*
+	 * In the GIC interrupt model, logical processors are
+	 * required to have a Processor Device object in the DSDT,
+	 * so we should check device_declaration here
+	 */
+	if (device_declaration && (gic->uid == acpi_id)) {
+		*apic_id = gic->gic_id;
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
 static int map_madt_entry(int type, u32 acpi_id)
 {
 	unsigned long madt_end, entry;
@@ -106,6 +128,9 @@ static int map_madt_entry(int type, u32 acpi_id)
 		} else if (header->type == ACPI_MADT_TYPE_LOCAL_SAPIC) {
 			if (!map_lsapic_id(header, type, acpi_id, &apic_id))
 				break;
+		} else if (header->type == ACPI_MADT_TYPE_GENERIC_INTERRUPT) {
+			if (!map_gic_id(header, type, acpi_id, &apic_id))
+				break;
 		}
 		entry += header->length;
 	}
@@ -136,6 +161,8 @@ static int map_mat_entry(acpi_handle handle, int type, u32 acpi_id)
 		map_lapic_id(header, acpi_id, &apic_id);
 	} else if (header->type == ACPI_MADT_TYPE_LOCAL_SAPIC) {
 		map_lsapic_id(header, type, acpi_id, &apic_id);
+	} else if (header->type == ACPI_MADT_TYPE_GENERIC_INTERRUPT) {
+		map_gic_id(header, type, acpi_id, &apic_id);
 	}
 
 exit: