[Qemu-devel] [PATCH v7] timer: a9gtimer: remove loop to auto-increment comparator

[P J P <ppandit@redhat.com>]

From: Prasad J Pandit <pjp@fedoraproject.org>

ARM A9MP processor has a peripheral timer with an auto-increment
register, which holds an increment step value. A user could set
this value to zero. When auto-increment control bit is enabled,
it leads to an infinite loop in 'a9_gtimer_update' while
updating comparator value. Remove this loop incrementing the
comparator value.

Reported-by: Li Qiang <liqiang6-s@360.cn>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
---
 hw/timer/a9gtimer.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

Use QEMU_ALIGN_UP instead of QEMU_ALIGN_DOWN
  -> https://lists.gnu.org/archive/html/qemu-devel/2016-10/msg03788.html

diff --git a/hw/timer/a9gtimer.c b/hw/timer/a9gtimer.c
index 772f85f..ce1dc63 100644
--- a/hw/timer/a9gtimer.c
+++ b/hw/timer/a9gtimer.c
@@ -82,15 +82,15 @@ static void a9_gtimer_update(A9GTimerState *s, bool sync)
         if ((s->control & R_CONTROL_TIMER_ENABLE) &&
                 (gtb->control & R_CONTROL_COMP_ENABLE)) {
             /* R2p0+, where the compare function is >= */
-            while (gtb->compare < update.new) {
+            if (gtb->compare < update.new) {
                 DB_PRINT("Compare event happened for CPU %d\n", i);
                 gtb->status = 1;
-                if (gtb->control & R_CONTROL_AUTO_INCREMENT) {
-                    DB_PRINT("Auto incrementing timer compare by %" PRId32 "\n",
-                             gtb->inc);
-                    gtb->compare += gtb->inc;
-                } else {
-                    break;
+                if (gtb->control & R_CONTROL_AUTO_INCREMENT && gtb->inc) {
+                    uint64_t inc =
+                        QEMU_ALIGN_UP(update.new - gtb->compare, gtb->inc);
+                    DB_PRINT("Auto incrementing timer compare by %"
+                                                        PRId64 "\n", inc);
+                    gtb->compare += inc;
                 }
             }
             cdiff = (int64_t)gtb->compare - (int64_t)update.new + 1;
-- 
2.7.4