genirq: Add a new IRQCHIP_EOI_THREADED flag

The flag is necessary for interrupt chips which require an ACK/EOI
after the handler has run. In case of threaded handlers this needs to
happen after the threaded handler has completed before the unmask of
the interrupt.

The flag is only unseful in combination with the handle_fasteoi_irq
flow control handler.

It can be combined with the flag IRQCHIP_EOI_IF_HANDLED, so the EOI is
not issued when the interrupt is disabled or in progress.

Tested-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-sunxi@googlegroups.com
Cc: Maxime Ripard <maxime.ripard@free-electrons.com>
Link: http://lkml.kernel.org/r/1394733834-26839-2-git-send-email-hdegoede@redhat.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/irq.h

@@ -356,6 +356,7 @@ struct irq_chip {
  *				when irq enabled
  * IRQCHIP_SKIP_SET_WAKE:	Skip chip.irq_set_wake(), for this irq chip
  * IRQCHIP_ONESHOT_SAFE:	One shot does not require mask/unmask
+ * IRQCHIP_EOI_THREADED:	Chip requires eoi() on unmask in threaded mode
  */
 enum {
 	IRQCHIP_SET_TYPE_MASKED		= (1 <<  0),
@@ -364,6 +365,7 @@ enum {
 	IRQCHIP_ONOFFLINE_ENABLED	= (1 <<  3),
 	IRQCHIP_SKIP_SET_WAKE		= (1 <<  4),
 	IRQCHIP_ONESHOT_SAFE		= (1 <<  5),
+	IRQCHIP_EOI_THREADED		= (1 <<  6),
 };
 
 /* This include will go away once we isolated irq_desc usage to core code */