On Thu, Jan 21, 2016 at 11:03 AM, Dmitry Osipenko <dig...@gmail.com> wrote:
> ptimer_get_count() might be called while QEMU timer already been expired.
> In that case ptimer would return counter = 0, which might be undesirable
> in case of polled timer. Do counter wrap around for periodic timer to keep
> it distributed. In order to achieve more accurate emulation behaviour of
> certain hardware, don't perform wrap around when in icount mode and return
> counter = 0 in that case (that doesn't affect polled counter distribution).
>
> Signed-off-by: Dmitry Osipenko <dig...@gmail.com>
Reviewed-by: Peter Crosthwaite <crosthwaite.pe...@gmail.com>
> ---
> hw/core/ptimer.c | 19 +++++++++++++------
> 1 file changed, 13 insertions(+), 6 deletions(-)
>
> diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c
> index 6dc1677..cb50d30 100644
> --- a/hw/core/ptimer.c
> +++ b/hw/core/ptimer.c
> @@ -83,14 +83,16 @@ static void ptimer_tick(void *opaque)
>
> uint64_t ptimer_get_count(ptimer_state *s)
> {
> - int64_t now;
> uint64_t counter;
>
> if (s->enabled) {
> - now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
> + int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
> + int64_t next = s->next_event;
> + bool expired = (now - next >= 0);
> + bool oneshot = (s->enabled == 2);
> +
> /* Figure out the current counter value. */
> - if (now - s->next_event > 0
> - || s->period == 0) {
> + if (s->period == 0 || (expired && (oneshot || use_icount))) {
> /* Prevent timer underflowing if it should already have
> triggered. */
> counter = 0;
> @@ -102,7 +104,7 @@ uint64_t ptimer_get_count(ptimer_state *s)
> uint32_t period_frac = s->period_frac;
> uint64_t period = s->period;
>
> - if ((s->enabled == 1) && !use_icount && (s->delta * period <
> 10000)) {
> + if (!oneshot && (s->delta * period < 10000) && !use_icount) {
> period = 10000 / s->delta;
> period_frac = 0;
> }
> @@ -117,7 +119,7 @@ uint64_t ptimer_get_count(ptimer_state *s)
> backwards.
> */
>
> - rem = s->next_event - now;
> + rem = expired ? now - next : next - now;
> div = period;
>
> clz1 = clz64(rem);
> @@ -137,6 +139,11 @@ uint64_t ptimer_get_count(ptimer_state *s)
> div += 1;
> }
> counter = rem / div;
> +
> + if (expired && (counter != 0)) {
> + /* Wrap around periodic counter. */
> + counter = s->limit - counter % s->limit;
> + }
> }
> } else {
> counter = s->delta;
> --
> 2.7.0
>
