/* 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;
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;