x86, ACPI, irq: Provide basic irqdomain support

Enhance ACPI driver to provide basic irqdomain support for IOAPIC.

We will build identity mapping for IOAPICs hosting legacy IRQs,
otherwise dynamically allocate IRQ numbers for IOAPIC pins on demand.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Grant Likely <grant.likely@linaro.org>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Len Brown <len.brown@intel.com>
Cc: Pavel Machek <pavel@ucw.cz>
Link: http://lkml.kernel.org/r/1402302011-23642-26-git-send-email-jiang.liu@linux.intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/acpi/boot.c

@@ -31,6 +31,7 @@
 #include <linux/module.h>
 #include <linux/dmi.h>
 #include <linux/irq.h>
+#include <linux/irqdomain.h>
 #include <linux/slab.h>
 #include <linux/bootmem.h>
 #include <linux/ioport.h>
@@ -449,10 +450,16 @@ static int mp_register_gsi(struct device *dev, u32 gsi, int trigger,
 	return irq;
 }
 
+static struct irq_domain_ops acpi_irqdomain_ops;
+
 static int __init
 acpi_parse_ioapic(struct acpi_subtable_header * header, const unsigned long end)
 {
 	struct acpi_madt_io_apic *ioapic = NULL;
+	struct ioapic_domain_cfg cfg = {
+		.type = IOAPIC_DOMAIN_DYNAMIC,
+		.ops = &acpi_irqdomain_ops,
+	};
 
 	ioapic = (struct acpi_madt_io_apic *)header;
 
@@ -461,8 +468,12 @@ acpi_parse_ioapic(struct acpi_subtable_header * header, const unsigned long end)
 
 	acpi_table_print_madt_entry(header);
 
-	mp_register_ioapic(ioapic->id,
-			   ioapic->address, ioapic->global_irq_base, NULL);
+	/* Statically assign IRQ numbers for IOAPICs hosting legacy IRQs */
+	if (ioapic->global_irq_base < nr_legacy_irqs())
+		cfg.type = IOAPIC_DOMAIN_LEGACY;
+
+	mp_register_ioapic(ioapic->id, ioapic->address, ioapic->global_irq_base,
+			   &cfg);
 
 	return 0;
 }