genirq; Add fasteoi irq_chip quirk

Some chips want irq_eoi() only called when an interrupt is actually
handled. So they have checks for INPROGRESS and DISABLED in their
irq_eoi callbacks. Add a chip flag, which allows to handle that in the
generic code. No impact on the fastpath.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/irq.h

@@ -328,10 +328,12 @@ struct irq_chip {
 /*
  * irq_chip specific flags
  *
- * IRQCHIP_SET_TYPE_MASKED:		Mask before calling chip.irq_set_type()
+ * IRQCHIP_SET_TYPE_MASKED:	Mask before calling chip.irq_set_type()
+ * IRQCHIP_EOI_IF_HANDLED:	Only issue irq_eoi() when irq was handled
  */
 enum {
 	IRQCHIP_SET_TYPE_MASKED		= (1 <<  0),
+	IRQCHIP_EOI_IF_HANDLED		= (1 <<  1),
 };
 
 /* This include will go away once we isolated irq_desc usage to core code */

kernel/irq/chip.c

@@ -515,9 +515,16 @@ handle_fasteoi_irq(unsigned int irq, struct irq_desc *desc)
 	}
 	preflow_handler(desc);
 	handle_irq_event(desc);
-out:
+
+out_eoi:
 	desc->irq_data.chip->irq_eoi(&desc->irq_data);
+out_unlock:
 	raw_spin_unlock(&desc->lock);
+	return;
+out:
+	if (!(desc->irq_data.chip->flags & IRQCHIP_EOI_IF_HANDLED))
+		goto out_eoi;
+	goto out_unlock;
 }
 
 /**