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authorPaolo Bonzini <pbonzini@redhat.com>2017-07-25 14:35:35 +0200
committerPaolo Bonzini <pbonzini@redhat.com>2017-08-01 17:27:33 +0200
commit6a51d83a17e8213db353dd6756685fd9e3513e13 (patch)
tree274c5cab24ed6b775265e4e640be52713eb8d726
parentda3a392f0562c1deffd2bc1258d2893bb397009c (diff)
downloadqemu-arm-6a51d83a17e8213db353dd6756685fd9e3513e13.tar.gz
mc146818rtc: simplify check_update_timer
Move all the optimized cases together, since they all have UF=1 in common. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rw-r--r--hw/timer/mc146818rtc.c24
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;