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RTC: Add divider reset support 

The first update cycle begins one-half seconds after divider
reset is removed.  This feature is useful for testing.

Signed-off-by: Yang Zhang <yang.z.zhang@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Yang Zhang 2012-08-02 18:04:10 +02:00 committed by Anthony Liguori
parent 56038ef623
commit 41a9b8b24d
1 changed files with 41 additions and 9 deletions
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50
hw/mc146818rtc.c
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@ -83,6 +83,12 @@ static void rtc_update_time(RTCState *s);
static void rtc_set_cmos(RTCState *s);
static inline int rtc_from_bcd(RTCState *s, int a);
static inline bool rtc_running(RTCState *s)
{
return (!(s->cmos_data[RTC_REG_B] & REG_B_SET) &&
(s->cmos_data[RTC_REG_A] & 0x70) <= 0x20);
}
static uint64_t get_guest_rtc_ns(RTCState *s)
{
uint64_t guest_rtc;
@ -199,11 +205,15 @@ static void check_update_timer(RTCState *s)
uint64_t next_update_time;
uint64_t guest_nsec;
/* From the data sheet: setting the SET bit does not prevent
* interrupts from occurring! However, it will prevent an
* alarm interrupt from occurring, because the time of day is
* not updated.
/* 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.
*/
if ((s->cmos_data[RTC_REG_A] & 0x60) == 0x60) {
qemu_del_timer(s->update_timer);
return;
}
if ((s->cmos_data[RTC_REG_C] & REG_C_UF) &&
(s->cmos_data[RTC_REG_B] & REG_B_SET)) {
qemu_del_timer(s->update_timer);
@ -268,6 +278,8 @@ static void rtc_update_timer(void *opaque)
int32_t irqs = REG_C_UF;
int32_t new_irqs;
assert((s->cmos_data[RTC_REG_A] & 0x60) != 0x60);
/* UIP might have been latched, update time and clear it. */
rtc_update_time(s);
s->cmos_data[RTC_REG_A] &= ~REG_A_UIP;
@ -312,12 +324,31 @@ static void cmos_ioport_write(void *opaque, uint32_t addr, uint32_t data)
case RTC_YEAR:
s->cmos_data[s->cmos_index] = data;
/* if in set mode, do not update the time */
if (!(s->cmos_data[RTC_REG_B] & REG_B_SET)) {
if (rtc_running(s)) {
rtc_set_time(s);
check_update_timer(s);
}
break;
case RTC_REG_A:
if ((data & 0x60) == 0x60) {
if (rtc_running(s)) {
rtc_update_time(s);
}
/* What happens to UIP when divider reset is enabled is
* unclear from the datasheet. Shouldn't matter much
* though.
*/
s->cmos_data[RTC_REG_A] &= ~REG_A_UIP;
} else if (((s->cmos_data[RTC_REG_A] & 0x60) == 0x60) &&
(data & 0x70) <= 0x20) {
/* when the divider reset is removed, the first update cycle
* begins one-half second later*/
if (!(s->cmos_data[RTC_REG_B] & REG_B_SET)) {
s->offset = 500000000;
rtc_set_time(s);
}
s->cmos_data[RTC_REG_A] &= ~REG_A_UIP;
}
/* UIP bit is read only */
s->cmos_data[RTC_REG_A] = (data & ~REG_A_UIP) |
(s->cmos_data[RTC_REG_A] & REG_A_UIP);
@ -327,7 +358,7 @@ static void cmos_ioport_write(void *opaque, uint32_t addr, uint32_t data)
case RTC_REG_B:
if (data & REG_B_SET) {
/* update cmos to when the rtc was stopping */
if (!(s->cmos_data[RTC_REG_B] & REG_B_SET)) {
if (rtc_running(s)) {
rtc_update_time(s);
}
/* set mode: reset UIP mode */
@ -335,7 +366,8 @@ static void cmos_ioport_write(void *opaque, uint32_t addr, uint32_t data)
data &= ~REG_B_UIE;
} else {
/* if disabling set mode, update the time */
if (s->cmos_data[RTC_REG_B] & REG_B_SET) {
if ((s->cmos_data[RTC_REG_B] & REG_B_SET) &&
(s->cmos_data[RTC_REG_A] & 0x70) <= 0x20) {
s->offset = get_guest_rtc_ns(s) % NSEC_PER_SEC;
rtc_set_time(s);
}
@ -449,7 +481,7 @@ static int update_in_progress(RTCState *s)
{
int64_t guest_nsec;
if (s->cmos_data[RTC_REG_B] & REG_B_SET) {
if (!rtc_running(s)) {
return 0;
}
if (qemu_timer_pending(s->update_timer)) {
@ -486,7 +518,7 @@ static uint32_t cmos_ioport_read(void *opaque, uint32_t addr)
case RTC_YEAR:
/* if not in set mode, calibrate cmos before
* reading*/
if (!(s->cmos_data[RTC_REG_B] & REG_B_SET)) {
if (rtc_running(s)) {
rtc_update_time(s);
}
ret = s->cmos_data[s->cmos_index];