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Re: [PATCH] mc146818rtc: fix timer interrupt reinjection
From: |
Paolo Bonzini |
Subject: |
Re: [PATCH] mc146818rtc: fix timer interrupt reinjection |
Date: |
Wed, 9 Oct 2019 23:13:16 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 |
On 09/10/19 20:40, Marcelo Tosatti wrote:
> s->period = period;
> lost_clock += old_irq_coalesced * old_period;
> - s->irq_coalesced = lost_clock / s->period;
> + if (old_period) {
> + s->irq_coalesced = lost_clock / s->period;
> + }
> +
> lost_clock %= s->period;
> if (old_irq_coalesced != s->irq_coalesced ||
> old_period != s->period) {
I think none of the code in the "if (s->lost_tick_policy ==
LOST_TICK_POLICY_SLEW) {" matters if old_period == 0 (and lost_clock
will always be 0). So perhaps we should place all that big "if" under
the existing "if (old_period)"?
Or even something like:
diff --git a/hw/timer/mc146818rtc.c b/hw/timer/mc146818rtc.c
index 6cb378751b..3337a8da98 100644
--- a/hw/timer/mc146818rtc.c
+++ b/hw/timer/mc146818rtc.c
@@ -202,25 +202,33 @@ periodic_timer_update(RTCState *s, int64_t current_time,
uint32_t old_period)
int64_t cur_clock, next_irq_clock, lost_clock = 0;
period = rtc_periodic_clock_ticks(s);
+ if (old_period && old_period == period) {
+ return;
+ }
- if (period) {
- /* compute 32 khz clock */
- cur_clock =
- muldiv64(current_time, RTC_CLOCK_RATE, NANOSECONDS_PER_SECOND);
+ if (!period) {
+ s->irq_coalesced = 0;
+ timer_del(s->periodic_timer);
+ return;
- /*
- * if the periodic timer's update is due to period re-configuration,
- * we should count the clock since last interrupt.
- */
- if (old_period) {
- int64_t last_periodic_clock, next_periodic_clock;
-
- next_periodic_clock = muldiv64(s->next_periodic_time,
- RTC_CLOCK_RATE, NANOSECONDS_PER_SECOND);
- last_periodic_clock = next_periodic_clock - old_period;
- lost_clock = cur_clock - last_periodic_clock;
- assert(lost_clock >= 0);
- }
+ }
+
+ /* compute 32 khz clock */
+ cur_clock =
+ muldiv64(current_time, RTC_CLOCK_RATE, NANOSECONDS_PER_SECOND);
+
+ /*
+ * if the periodic timer's update is due to period re-configuration,
+ * we should count the clock since last interrupt.
+ */
+ if (old_period) {
+ int64_t last_periodic_clock, next_periodic_clock;
+
+ next_periodic_clock = muldiv64(s->next_periodic_time,
+ RTC_CLOCK_RATE, NANOSECONDS_PER_SECOND);
+ last_periodic_clock = next_periodic_clock - old_period;
+ lost_clock = cur_clock - last_periodic_clock;
+ assert(lost_clock >= 0);
/*
* s->irq_coalesced can change for two reasons:
@@ -243,13 +251,10 @@ periodic_timer_update(RTCState *s, int64_t current_time,
uint32_t old_period)
lost_clock += old_irq_coalesced * old_period;
s->irq_coalesced = lost_clock / s->period;
lost_clock %= s->period;
- if (old_irq_coalesced != s->irq_coalesced ||
- old_period != s->period) {
- DPRINTF_C("cmos: coalesced irqs scaled from %d to %d, "
- "period scaled from %d to %d\n", old_irq_coalesced,
- s->irq_coalesced, old_period, s->period);
- rtc_coalesced_timer_update(s);
- }
+ DPRINTF_C("cmos: coalesced irqs scaled from %d to %d, "
+ "period scaled from %d to %d\n", old_irq_coalesced,
+ s->irq_coalesced, old_period, s->period);
+ rtc_coalesced_timer_update(s);
} else {
/*
* no way to compensate the interrupt if LOST_TICK_POLICY_SLEW
@@ -257,16 +262,12 @@ periodic_timer_update(RTCState *s, int64_t current_time,
uint32_t old_period)
*/
lost_clock = MIN(lost_clock, period);
}
-
assert(lost_clock >= 0 && lost_clock <= period);
-
- next_irq_clock = cur_clock + period - lost_clock;
- s->next_periodic_time = periodic_clock_to_ns(next_irq_clock) + 1;
- timer_mod(s->periodic_timer, s->next_periodic_time);
- } else {
- s->irq_coalesced = 0;
- timer_del(s->periodic_timer);
}
+
+ next_irq_clock = cur_clock + period - lost_clock;
+ s->next_periodic_time = periodic_clock_to_ns(next_irq_clock) + 1;
+ timer_mod(s->periodic_timer, s->next_periodic_time);
}
static void rtc_periodic_timer(void *opaque)
Best read with "diff -b".
Paolo