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ptimer: Add TRIGGER_ONLY_ON_DECREMENT policy option

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The CMSDK timer behaviour is that an interrupt is triggered when the
counter counts down from 1 to 0; however one is not triggered if the
counter is manually set to 0 by a guest write to the counter register.
Currently ptimer can't handle this; add a policy option to allow
a ptimer user to request this behaviour.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Message-id: 20180703171044.9503-2-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2018-07-09 14:51:34 +01:00
parent b78aae9bb6
commit 086ede32af
3 changed files with 49 additions and 7 deletions
Download patch file Download diff file Expand all files Collapse all files

22
hw/core/ptimer.c
View file

@ -45,8 +45,20 @@ static void ptimer_reload(ptimer_state *s, int delta_adjust)
uint32_t period_frac = s->period_frac;
uint64_t period = s->period;
uint64_t delta = s->delta;
bool suppress_trigger = false;
if (delta == 0 && !(s->policy_mask & PTIMER_POLICY_NO_IMMEDIATE_TRIGGER)) {
/*
* Note that if delta_adjust is 0 then we must be here because of
* a count register write or timer start, not because of timer expiry.
* In that case the policy might require us to suppress the timer trigger
* that we would otherwise generate for a zero delta.
*/
if (delta_adjust == 0 &&
(s->policy_mask & PTIMER_POLICY_TRIGGER_ONLY_ON_DECREMENT)) {
suppress_trigger = true;
}
if (delta == 0 && !(s->policy_mask & PTIMER_POLICY_NO_IMMEDIATE_TRIGGER)
&& !suppress_trigger) {
ptimer_trigger(s);
}
@ -353,6 +365,14 @@ ptimer_state *ptimer_init(QEMUBH *bh, uint8_t policy_mask)
s->bh = bh;
s->timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, ptimer_tick, s);
s->policy_mask = policy_mask;
/*
* These two policies are incompatible -- trigger-on-decrement implies
* a timer trigger when the count becomes 0, but no-immediate-trigger
* implies a trigger when the count stops being 0.
*/
assert(!((policy_mask & PTIMER_POLICY_TRIGGER_ONLY_ON_DECREMENT) &&
(policy_mask & PTIMER_POLICY_NO_IMMEDIATE_TRIGGER)));
return s;
}