diff options
| -rw-r--r-- | hw/timer/mc146818rtc.c | 24 |
1 files changed, 11 insertions, 13 deletions
diff --git a/hw/timer/mc146818rtc.c b/hw/timer/mc146818rtc.c index 1b8d3d7d4c..ffb2c6a33e 100644 --- a/hw/timer/mc146818rtc.c +++ b/hw/timer/mc146818rtc.c @@ -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; |