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Re: [Qemu-devel] [PATCH v3] timer: a9gtimer: remove loop to auto-increme
From: |
Peter Maydell |
Subject: |
Re: [Qemu-devel] [PATCH v3] timer: a9gtimer: remove loop to auto-increment comparator |
Date: |
Fri, 7 Oct 2016 15:30:57 +0100 |
On 3 October 2016 at 10:04, P J P <address@hidden> wrote:
> From: Prasad J Pandit <address@hidden>
>
> 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 <address@hidden>
> Signed-off-by: Prasad J Pandit <address@hidden>
> ---
> hw/timer/a9gtimer.c | 16 ++++++++--------
> 1 file changed, 8 insertions(+), 8 deletions(-)
>
> Update per:
> -> https://lists.gnu.org/archive/html/qemu-devel/2016-10/msg00079.html
>
> diff --git a/hw/timer/a9gtimer.c b/hw/timer/a9gtimer.c
> index 772f85f..add2f31 100644
> --- a/hw/timer/a9gtimer.c
> +++ b/hw/timer/a9gtimer.c
> @@ -73,6 +73,7 @@ static void a9_gtimer_update(A9GTimerState *s, bool sync)
>
> A9GTimerUpdate update = a9_gtimer_get_update(s);
> int i;
> + uint64_t inc;
> int64_t next_cdiff = 0;
>
> for (i = 0; i < s->num_cpu; ++i) {
> @@ -82,16 +83,15 @@ 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
> + && gtb->control & R_CONTROL_AUTO_INCREMENT) {
> 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;
> - }
> + inc = update.new - gtb->compare - 1;
> + inc = gtb->inc ? QEMU_ALIGN_DOWN(inc, gtb->inc) : 0;
> + DB_PRINT("Auto incrementing timer compare by %"
> + PRId64 "\n", inc);
> + gtb->compare += inc;
> }
> cdiff = (int64_t)gtb->compare - (int64_t)update.new + 1;
> if (cdiff > 0 && (cdiff < next_cdiff || !next_cdiff)) {
This is still losing the setting of gtb->status in the
case where the auto-increment bit is not set.
thanks
-- PMM