Commit ec2db7de authored by pbrook's avatar pbrook
Browse files

ARM timer counts down, not up.


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@2214 c046a42c-6fe2-441c-8c8c-71466251a162
parent 417f38f0
......@@ -107,29 +107,29 @@ static void arm_timer_update(arm_timer_state *s, int64_t now)
/* Return the current value of the timer. */
static uint32_t arm_timer_getcount(arm_timer_state *s, int64_t now)
{
int64_t elapsed;
int64_t left;
int64_t period;
if (s->count == 0)
return 0;
if ((s->control & TIMER_CTRL_ENABLE) == 0)
return s->count;
elapsed = now - s->loaded;
left = s->expires - now;
period = s->expires - s->loaded;
/* If the timer should have expired then return 0. This can happen
when the host timer signal doesnt occur immediately. It's better to
have a timer appear to sit at zero for a while than have it wrap
around before the guest interrupt is raised. */
/* ??? Could we trigger the interrupt here? */
if (elapsed > period)
if (left < 0)
return 0;
/* We need to calculate count * elapsed / period without overfowing.
Scale both elapsed and period so they fit in a 32-bit int. */
while (period != (int32_t)period) {
period >>= 1;
elapsed >>= 1;
left >>= 1;
}
return ((uint64_t)s->count * (uint64_t)(int32_t)elapsed)
return ((uint64_t)s->count * (uint64_t)(int32_t)left)
/ (int32_t)period;
}
......
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