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mc146818rtc: simplify check_update_timer

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Move all the optimized cases together, since they all have UF=1 in
common.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2017-07-25 14:35:35 +02:00
parent da3a392f05
commit 6a51d83a17
1 changed files with 11 additions and 13 deletions
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24
hw/timer/mc146818rtc.c
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@ -291,26 +291,14 @@ static void check_update_timer(RTCState *s)
/* From the data sheet: "Holding the dividers in reset prevents
* interrupts from operating, while setting the SET bit allows"
* them to occur. However, it will prevent an alarm interrupt
* from occurring, because the time of day is not updated.
* them to occur.
*/
if ((s->cmos_data[RTC_REG_A] & 0x60) == 0x60) {
timer_del(s->update_timer);
return;
}
if ((s->cmos_data[RTC_REG_C] & REG_C_UF) &&
(s->cmos_data[RTC_REG_B] & REG_B_SET)) {
timer_del(s->update_timer);
return;
}
if ((s->cmos_data[RTC_REG_C] & REG_C_UF) &&
(s->cmos_data[RTC_REG_C] & REG_C_AF)) {
timer_del(s->update_timer);
return;
}
guest_nsec = get_guest_rtc_ns(s) % NANOSECONDS_PER_SECOND;
/* if UF is clear, reprogram to next second */
next_update_time = qemu_clock_get_ns(rtc_clock)
+ NANOSECONDS_PER_SECOND - guest_nsec;
@ -321,7 +309,17 @@ static void check_update_timer(RTCState *s)
s->next_alarm_time = next_update_time +
(next_alarm_sec - 1) * NANOSECONDS_PER_SECOND;
/* If UF is already set, we might be able to optimize. */
if (s->cmos_data[RTC_REG_C] & REG_C_UF) {
/* If AF cannot change (i.e. either it is set already, or
* SET=1 and then the time is not updated), nothing to do.
*/
if ((s->cmos_data[RTC_REG_B] & REG_B_SET) ||
(s->cmos_data[RTC_REG_C] & REG_C_AF)) {
timer_del(s->update_timer);
return;
}
/* UF is set, but AF is clear. Program the timer to target
* the alarm time. */
next_update_time = s->next_alarm_time;