Fix very high interrupt rate for IRQ8 (rtc) unless pnpacpi=off

Workaround for broken systems with BIOS that makes RTC interrupt level
triggered and/or active low.

See http://bugzilla.kernel.org/show_bug.cgi?id=5243

Based on the patch from Shaohua Li <shaohua.li@intel.com>
Signed-off-by: NKrzysztof Piotr Oledzki <ole@ans.pl>
Cc: "Li, Shaohua" <shaohua.li@intel.com>
Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Adam Belay <ambx1@neo.rr.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/pnp/pnpacpi/rsparser.c

@@ -85,6 +85,16 @@ static void pnpacpi_parse_allocated_irqresource(struct pnp_resource_table *res,
 	if (i >= PNP_MAX_IRQ)
 		return;
 
+#ifdef CONFIG_X86
+	if (gsi < 16 && (triggering != ACPI_EDGE_SENSITIVE ||
+				polarity != ACPI_ACTIVE_HIGH)) {
+		pnp_warn("BIOS BUG: legacy PNP IRQ %d should be edge trigger, "
+				"active high", gsi);
+		triggering = ACPI_EDGE_SENSITIVE;
+		polarity = ACPI_ACTIVE_HIGH;
+	}
+#endif
+
 	res->irq_resource[i].flags = IORESOURCE_IRQ;	// Also clears _UNSET flag
 	res->irq_resource[i].flags |= irq_flags(triggering, polarity);
 	irq = acpi_register_gsi(gsi, triggering, polarity);