On Sat, Jan 30, 2016 at 8:43 AM, Dmitry Osipenko <dig...@gmail.com> wrote:
> It might be necessary by some emulated HW to perform the tick after one
> period if delta = 0. Given that it is much less churny to implement immediate
> tick by the ptimer user itself, let's make ptimer do the delayed tick.
>
Isn't this related to previous patch? It is kind of a rounding problem
that will vary from timer to timer. Some timers may interpret the
"tick" as the wrap-around back to the load value (even if that is 0)
while others interpret the tick as the transition to zero (makes more
sense for a one-shot). It's hard to set a universal policy here.
But is this a non-issue when we consider that event latency (usually
interrupt latency) is undefined anyway?
Regards,
Peter
> Signed-off-by: Dmitry Osipenko <dig...@gmail.com>
> ---
> hw/core/ptimer.c | 34 +++++++++++++++-------------------
> 1 file changed, 15 insertions(+), 19 deletions(-)
>
> diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c
> index b2044fb..bcd090c 100644
> --- a/hw/core/ptimer.c
> +++ b/hw/core/ptimer.c
> @@ -36,19 +36,7 @@ static void ptimer_reload(ptimer_state *s)
> {
> uint32_t period_frac = s->period_frac;
> uint64_t period = s->period;
> -
> - if (s->delta == 0) {
> - ptimer_trigger(s);
> - }
> -
> - if (s->delta == 0 && s->enabled == 1) {
> - s->delta = s->limit;
> - }
> -
> - if (s->delta == 0) {
> - ptimer_stop(s);
> - return;
> - }
> + uint64_t delta = MAX(1, s->delta);
>
> /*
> * Artificially limit timeout rate to something
> @@ -59,15 +47,15 @@ static void ptimer_reload(ptimer_state *s)
> * on the current generation of host machines.
> */
>
> - if (s->enabled == 1 && (s->delta * period < 10000) && !use_icount) {
> - period = 10000 / s->delta;
> + if (s->enabled == 1 && (delta * period < 10000) && !use_icount) {
> + period = 10000 / delta;
> period_frac = 0;
> }
>
> s->last_event = s->next_event;
> - s->next_event = s->last_event + s->delta * period;
> + s->next_event = s->last_event + delta * period;
> if (period_frac) {
> - s->next_event += ((int64_t)period_frac * s->delta) >> 32;
> + s->next_event += ((int64_t)period_frac * delta) >> 32;
> }
> timer_mod(s->timer, s->next_event);
> }
> @@ -75,8 +63,16 @@ static void ptimer_reload(ptimer_state *s)
> static void ptimer_tick(void *opaque)
> {
> ptimer_state *s = (ptimer_state *)opaque;
> - s->delta = 0;
> - ptimer_reload(s);
> +
> + s->delta = (s->enabled == 1) ? s->limit : 0;
> +
> + if (s->delta == 0) {
> + s->enabled = 0;
> + } else {
> + ptimer_reload(s);
> + }
> +
> + ptimer_trigger(s);
> }
>
> uint64_t ptimer_get_count(ptimer_state *s)
> --
> 2.7.0
>
