Commit 5a50307b authored by Dmitry Osipenko's avatar Dmitry Osipenko Committed by Peter Maydell
Browse files

hw/ptimer: Perform counter wrap around if timer already expired 



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: default avatarDmitry Osipenko <digetx@gmail.com>
Reviewed-by: default avatarPeter Crosthwaite <crosthwaite.peter@gmail.com>
Message-id: 4ce381c7d24d85d165ff251d2875d16a4b6a5c04.1464367869.git.digetx@gmail.com
Signed-off-by: default avatarPeter Maydell <peter.maydell@linaro.org>
parent e91171e3

hw/core/ptimer.c

+13 −6
Original line number Diff line number Diff line
@@ -84,14 +84,16 @@ 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;
@@ -103,7 +105,7 @@ 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;

            }
@@ -118,7 +120,7 @@ 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);
@@ -138,6 +140,11 @@ 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 - 1) % s->limit;

            }

        }

    } else {

        counter = s->delta;