[PATCH v2 3/3] irqchip: orion: clear stale interrupts in irq_startup

[sebastian.hesselbarth@gmail.com (Sebastian Hesselbarth)]

Bridge IRQ_CAUSE bits are asserted regardless of the corresponding bit in
IRQ_MASK register. To avoid interrupt events on stale irqs, we have to clear
them before unmask. This installs an .irq_startup callback to ensure stale
irqs are cleared before initial unmask.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
---
Changelog:
v1->v2:
- use .irq_startup instead of .irq_enable (Reported by Jason Gunthorpe)

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Gregory Clement <gregory.clement@free-electrons.com>
Cc: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Cc: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Cc: linux-arm-kernel at lists.infradead.org
Cc: linux-kernel at vger.kernel.org
---
 drivers/irqchip/irq-orion.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/irqchip/irq-orion.c b/drivers/irqchip/irq-orion.c
index 1f636f719065..0dfdc5c824a1 100644
--- a/drivers/irqchip/irq-orion.c
+++ b/drivers/irqchip/irq-orion.c
@@ -123,6 +123,19 @@ static void orion_bridge_irq_handler(unsigned int irq, struct irq_desc *desc)
 	}
 }
 
+/*
+ * Bridge IRQ_CAUSE is asserted regardless of IRQ_MASK register.
+ * To avoid interrupt events on stale irqs, we clear them before unmask.
+ */
+static unsigned int orion_bridge_irq_startup(struct irq_data *d)
+{
+	struct irq_chip_type *ct = irq_data_get_chip_type(d);
+
+	ct->chip.irq_ack(d);
+	ct->chip.irq_unmask(d);
+	return 0;
+}
+
 static int __init orion_bridge_irq_init(struct device_node *np,
 					struct device_node *parent)
 {
@@ -176,6 +189,7 @@ static int __init orion_bridge_irq_init(struct device_node *np,
 
 	gc->chip_types[0].regs.ack = ORION_BRIDGE_IRQ_CAUSE;
 	gc->chip_types[0].regs.mask = ORION_BRIDGE_IRQ_MASK;
+	gc->chip_types[0].chip.irq_startup = orion_bridge_irq_startup;
 	gc->chip_types[0].chip.irq_ack = irq_gc_ack_clr_bit;
 	gc->chip_types[0].chip.irq_mask = irq_gc_mask_clr_bit;
 	gc->chip_types[0].chip.irq_unmask = irq_gc_mask_set_bit;
-- 
1.8.5.2