irqchip: sun4i: Fix irq 0 not working

SUN4I_IRQ_VECTOR_REG containing 0 can mean one of 3 things:

1) no more irqs pending
2) irq 0 pending
3) spurious irq

So if we immediately get a reading of 0, check the irq-pending reg
to differentiate between 2 and 3. We only do this once to avoid
the extra check in the common case of 1) hapening after having
read the vector-reg once.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-sunxi@googlegroups.com
Link: http://lkml.kernel.org/r/1394733834-26839-3-git-send-email-hdegoede@redhat.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 16 insertions, 2 deletions

diff --git a/drivers/irqchip/irq-sun4i.c b/drivers/irqchip/irq-sun4i.c
index 15999551ff7f..7ae85ec61e56 100644
--- a/drivers/irqchip/irq-sun4i.c
+++ b/drivers/irqchip/irq-sun4i.c
@@ -140,10 +140,24 @@ static void __exception_irq_entry sun4i_handle_irq(struct pt_regs *regs)
 {
         u32 irq, hwirq;
 
+        /*
+         * hwirq == 0 can mean one of 3 things:
+         * 1) no more irqs pending
+         * 2) irq 0 pending
+         * 3) spurious irq
+         * So if we immediately get a reading of 0, check the irq-pending reg
+         * to differentiate between 2 and 3. We only do this once to avoid
+         * the extra check in the common case of 1 hapening after having
+         * read the vector-reg once.
+         */
         hwirq = readl(sun4i_irq_base + SUN4I_IRQ_VECTOR_REG) >> 2;
-        while (hwirq != 0) {
+        if (hwirq == 0 &&
+                  !(readl(sun4i_irq_base + SUN4I_IRQ_PENDING_REG(0)) & BIT(0)))
+                return;
+
+        do {
                 irq = irq_find_mapping(sun4i_irq_domain, hwirq);
                 handle_IRQ(irq, regs);
                 hwirq = readl(sun4i_irq_base + SUN4I_IRQ_VECTOR_REG) >> 2;
-        }
+        } while (hwirq != 0);
 }