x86: irq: Fix bug in setting IOAPIC pin attributes

Commit 15a3c7cc9154321fc3 "x86, irq: Introduce two helper functions
to support irqdomain map operation" breaks LPSS ACPI enumerated
devices.

On startup, IOAPIC driver preallocates IRQ descriptors and programs
IOAPIC pins with default level and polarity attributes for all legacy
IRQs. Later legacy IRQ users may fail to set IOAPIC pin attributes
if the requested attributes conflicts with the default IOAPIC pin
attributes. So change mp_irqdomain_map() to allow the first legacy IRQ
user to reprogram IOAPIC pin with different attributes.

Reported-and-tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.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: Borislav Petkov <bp@alien8.de>
Cc: Grant Likely <grant.likely@linaro.org>
Cc: Prarit Bhargava <prarit@redhat.com>
Link: http://lkml.kernel.org/r/1409118795-17046-1-git-send-email-jiang.liu@linux.intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/apic/io_apic.c

@@ -1070,6 +1070,11 @@ static int mp_map_pin_to_irq(u32 gsi, int idx, int ioapic, int pin,
 	}
 
 	if (flags & IOAPIC_MAP_ALLOC) {
+		/* special handling for legacy IRQs */
+		if (irq < nr_legacy_irqs() && info->count == 1 &&
+		    mp_irqdomain_map(domain, irq, pin) != 0)
+			irq = -1;
+
 		if (irq > 0)
 			info->count++;
 		else if (info->count == 0)
@@ -3896,7 +3901,15 @@ int mp_irqdomain_map(struct irq_domain *domain, unsigned int virq,
 			info->polarity = 1;
 		}
 		info->node = NUMA_NO_NODE;
-		info->set = 1;
+
+		/*
+		 * setup_IO_APIC_irqs() programs all legacy IRQs with default
+		 * trigger and polarity attributes. Don't set the flag for that
+		 * case so the first legacy IRQ user could reprogram the pin
+		 * with real trigger and polarity attributes.
+		 */
+		if (virq >= nr_legacy_irqs() || info->count)
+			info->set = 1;
 	}
 	set_io_apic_irq_attr(&attr, ioapic, hwirq, info->trigger,
 			     info->polarity);