diff options
Diffstat (limited to 'hw/timer/mc146818rtc.c')
| -rw-r--r-- | hw/timer/mc146818rtc.c | 120 |
1 files changed, 97 insertions, 23 deletions
diff --git a/hw/timer/mc146818rtc.c b/hw/timer/mc146818rtc.c index 7d78391b62..aeb60cc3e3 100644 --- a/hw/timer/mc146818rtc.c +++ b/hw/timer/mc146818rtc.c @@ -146,31 +146,100 @@ static void rtc_coalesced_timer(void *opaque) } #endif -/* handle periodic timer */ -static void periodic_timer_update(RTCState *s, int64_t current_time) +static uint32_t rtc_periodic_clock_ticks(RTCState *s) { - int period_code, period; - int64_t cur_clock, next_irq_clock; + int period_code; + + if (!(s->cmos_data[RTC_REG_B] & REG_B_PIE)) { + return 0; + } period_code = s->cmos_data[RTC_REG_A] & 0x0f; - if (period_code != 0 - && (s->cmos_data[RTC_REG_B] & REG_B_PIE)) { - if (period_code <= 2) - period_code += 7; - /* period in 32 Khz cycles */ - period = 1 << (period_code - 1); -#ifdef TARGET_I386 - if (period != s->period) { - s->irq_coalesced = (s->irq_coalesced * s->period) / period; - DPRINTF_C("cmos: coalesced irqs scaled to %d\n", s->irq_coalesced); - } - s->period = period; -#endif + if (!period_code) { + return 0; + } + + if (period_code <= 2) { + period_code += 7; + } + + /* period in 32 Khz cycles */ + return 1 << (period_code - 1); +} + +/* + * handle periodic timer. @old_period indicates the periodic timer update + * is just due to period adjustment. + */ +static void +periodic_timer_update(RTCState *s, int64_t current_time, uint32_t old_period) +{ + uint32_t period; + int64_t cur_clock, next_irq_clock, lost_clock = 0; + + period = rtc_periodic_clock_ticks(s); + + if (period) { /* compute 32 khz clock */ cur_clock = muldiv64(current_time, RTC_CLOCK_RATE, NANOSECONDS_PER_SECOND); - next_irq_clock = (cur_clock & ~(period - 1)) + period; + /* + * if the periodic timer's update is due to period re-configuration, + * we should count the clock since last interrupt. + */ + if (old_period) { + int64_t last_periodic_clock, next_periodic_clock; + + next_periodic_clock = muldiv64(s->next_periodic_time, + RTC_CLOCK_RATE, NANOSECONDS_PER_SECOND); + last_periodic_clock = next_periodic_clock - old_period; + lost_clock = cur_clock - last_periodic_clock; + assert(lost_clock >= 0); + } + +#ifdef TARGET_I386 + /* + * s->irq_coalesced can change for two reasons: + * + * a) if one or more periodic timer interrupts have been lost, + * lost_clock will be more that a period. + * + * b) when the period may be reconfigured, we expect the OS to + * treat delayed tick as the new period. So, when switching + * from a shorter to a longer period, scale down the missing, + * because the OS will treat past delayed ticks as longer + * (leftovers are put back into lost_clock). When switching + * to a shorter period, scale up the missing ticks since the + * OS handler will treat past delayed ticks as shorter. + */ + if (s->lost_tick_policy == LOST_TICK_POLICY_SLEW) { + uint32_t old_irq_coalesced = s->irq_coalesced; + + s->period = period; + lost_clock += old_irq_coalesced * old_period; + s->irq_coalesced = lost_clock / s->period; + lost_clock %= s->period; + if (old_irq_coalesced != s->irq_coalesced || + old_period != s->period) { + DPRINTF_C("cmos: coalesced irqs scaled from %d to %d, " + "period scaled from %d to %d\n", old_irq_coalesced, + s->irq_coalesced, old_period, s->period); + rtc_coalesced_timer_update(s); + } + } else +#endif + { + /* + * no way to compensate the interrupt if LOST_TICK_POLICY_SLEW + * is not used, we should make the time progress anyway. + */ + lost_clock = MIN(lost_clock, period); + } + + assert(lost_clock >= 0 && lost_clock <= period); + + next_irq_clock = cur_clock + period - lost_clock; s->next_periodic_time = muldiv64(next_irq_clock, NANOSECONDS_PER_SECOND, RTC_CLOCK_RATE) + 1; timer_mod(s->periodic_timer, s->next_periodic_time); @@ -186,7 +255,7 @@ static void rtc_periodic_timer(void *opaque) { RTCState *s = opaque; - periodic_timer_update(s, s->next_periodic_time); + periodic_timer_update(s, s->next_periodic_time, 0); s->cmos_data[RTC_REG_C] |= REG_C_PF; if (s->cmos_data[RTC_REG_B] & REG_B_PIE) { s->cmos_data[RTC_REG_C] |= REG_C_IRQF; @@ -391,6 +460,7 @@ static void cmos_ioport_write(void *opaque, hwaddr addr, uint64_t data, unsigned size) { RTCState *s = opaque; + uint32_t old_period; bool update_periodic_timer; if ((addr & 1) == 0) { @@ -425,6 +495,7 @@ static void cmos_ioport_write(void *opaque, hwaddr addr, break; case RTC_REG_A: update_periodic_timer = (s->cmos_data[RTC_REG_A] ^ data) & 0x0f; + old_period = rtc_periodic_clock_ticks(s); if ((data & 0x60) == 0x60) { if (rtc_running(s)) { @@ -450,7 +521,8 @@ static void cmos_ioport_write(void *opaque, hwaddr addr, (s->cmos_data[RTC_REG_A] & REG_A_UIP); if (update_periodic_timer) { - periodic_timer_update(s, qemu_clock_get_ns(rtc_clock)); + periodic_timer_update(s, qemu_clock_get_ns(rtc_clock), + old_period); } check_update_timer(s); @@ -458,6 +530,7 @@ static void cmos_ioport_write(void *opaque, hwaddr addr, case RTC_REG_B: update_periodic_timer = (s->cmos_data[RTC_REG_B] ^ data) & REG_B_PIE; + old_period = rtc_periodic_clock_ticks(s); if (data & REG_B_SET) { /* update cmos to when the rtc was stopping */ @@ -487,7 +560,8 @@ static void cmos_ioport_write(void *opaque, hwaddr addr, s->cmos_data[RTC_REG_B] = data; if (update_periodic_timer) { - periodic_timer_update(s, qemu_clock_get_ns(rtc_clock)); + periodic_timer_update(s, qemu_clock_get_ns(rtc_clock), + old_period); } check_update_timer(s); @@ -757,7 +831,7 @@ static int rtc_post_load(void *opaque, int version_id) uint64_t now = qemu_clock_get_ns(rtc_clock); if (now < s->next_periodic_time || now > (s->next_periodic_time + get_max_clock_jump())) { - periodic_timer_update(s, qemu_clock_get_ns(rtc_clock)); + periodic_timer_update(s, qemu_clock_get_ns(rtc_clock), 0); } } @@ -822,7 +896,7 @@ static void rtc_notify_clock_reset(Notifier *notifier, void *data) int64_t now = *(int64_t *)data; rtc_set_date_from_host(ISA_DEVICE(s)); - periodic_timer_update(s, now); + periodic_timer_update(s, now, 0); check_update_timer(s); #ifdef TARGET_I386 if (s->lost_tick_policy == LOST_TICK_POLICY_SLEW) { |