[PATCH] hw/timer/a9gtimer: Clear pending interrupt, after the clear of Event flag

[Vaclav Vanc]

A9 Global Timer is used with Edge triggered interrupts (This is true
at least for Zynq and i.MX6 processors).
When Event Flag is cleared in Interrupt Status Register and new interrupt
was supposed to be scheduled, interrupt request is never cleared.
Since interrupt in GIC is configured as Edge triggered, new interrupts
are not registered (because interrupt is stuck at pending and GIC thinks
it was already serviced). As a result interrupts from timer does not work
anymore.

Note: This happens only when interrupt was not serviced before the next
interrupt is suppose to be scheduled. This happens for example during
the increased load of the host system.

Interrupt is now always cleared when Event Flag is cleared.
This is in accordance to A9 Global Timer documentation.

Signed-off-by: Vaclav Vanc <vav@sysgo.com>
---
 hw/timer/a9gtimer.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/hw/timer/a9gtimer.c b/hw/timer/a9gtimer.c
index 7233068a37..732889105e 100644
--- a/hw/timer/a9gtimer.c
+++ b/hw/timer/a9gtimer.c
@@ -206,6 +206,9 @@ static void a9_gtimer_write(void *opaque, hwaddr addr, 
uint64_t value,
     case R_INTERRUPT_STATUS:
         a9_gtimer_update(s, false);
         gtb->status &= ~value;
+        if (gtb->status == 0) {
+            qemu_set_irq(gtb->irq, 0);
+        }
         break;
     case R_COMPARATOR_HI:
         shift = 32;
-- 
2.20.1