| Message ID | 20170412095111.11728-3-xiaoguangrong@tencent.com |
|---|---|
| State | New |
| Headers | show |
On 12/04/2017 11:51, guangrong.xiao@gmail.com wrote: > + int current_irq_coalesced = s->irq_coalesced; > + > + s->irq_coalesced = (current_irq_coalesced * s->period) / period; > + > + /* > + * calculate the lost clock after it is scaled which should be > + * compensated in the next interrupt. > + */ > + lost_clock += current_irq_coalesced * s->period - > + s->irq_coalesced * period; This is: lost_clock = current_irq_coalesced * s->period - (current_irq_coalesced * s->period) / period * period; i.e. /* When switching from a shorter to a longer period, scale down the * missing ticks since we expect the OS handler to treat the delayed * ticks as longer. Any leftovers are put back into next_irq_clock. * * When switching to a shorter period, scale up the missing ticks * since we expect the OS handler to treat the delayed ticks as * shorter. */ lost_clock = (s->irq_coalesced * s->period) % period; s->irq_coalesced = (s->irq_coalesced * s->period) / period; Is this correct? Paolo > + DPRINTF_C("cmos: coalesced irqs scaled from %d to %d, %ld clocks " > + "are compensated.\n", > + current_irq_coalesced, s->irq_coalesced, lost_clock); > } > s->period = period; > #endif > @@ -170,7 +193,7 @@ static void periodic_timer_update(RTCState *s, int64_t current_time) > cur_clock = > muldiv64(current_time, RTC_CLOCK_RATE, NANOSECONDS_PER_SECOND); > > - next_irq_clock = (cur_clock & ~(period - 1)) + 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); > --
On 05/03/2017 11:15 PM, Paolo Bonzini wrote: > > > On 12/04/2017 11:51, guangrong.xiao@gmail.com wrote: >> + int current_irq_coalesced = s->irq_coalesced; >> + >> + s->irq_coalesced = (current_irq_coalesced * s->period) / period; >> + >> + /* >> + * calculate the lost clock after it is scaled which should be >> + * compensated in the next interrupt. >> + */ >> + lost_clock += current_irq_coalesced * s->period - >> + s->irq_coalesced * period; > > This is: > > lost_clock = current_irq_coalesced * s->period - > (current_irq_coalesced * s->period) / period * period; > > i.e. > > /* When switching from a shorter to a longer period, scale down the > * missing ticks since we expect the OS handler to treat the delayed > * ticks as longer. Any leftovers are put back into next_irq_clock. > * > * When switching to a shorter period, scale up the missing ticks > * since we expect the OS handler to treat the delayed ticks as > * shorter. > */ > lost_clock = (s->irq_coalesced * s->period) % period; > s->irq_coalesced = (s->irq_coalesced * s->period) / period; > > Is this correct? > Yes, it is correct, it looks smarter, will apply it in the next version. Thanks!
diff --git a/hw/timer/mc146818rtc.c b/hw/timer/mc146818rtc.c index 749e206..649678c 100644 --- a/hw/timer/mc146818rtc.c +++ b/hw/timer/mc146818rtc.c @@ -146,23 +146,46 @@ static void rtc_coalesced_timer(void *opaque) } #endif +static int period_code_to_clock(int period_code) +{ + /* periodic timer is disabled. */ + 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 */ static void periodic_timer_update(RTCState *s, int64_t current_time) { int period_code, period; - int64_t cur_clock, next_irq_clock; + int64_t cur_clock, next_irq_clock, lost_clock = 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); + period = period_code_to_clock(period_code); #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); + int current_irq_coalesced = s->irq_coalesced; + + s->irq_coalesced = (current_irq_coalesced * s->period) / period; + + /* + * calculate the lost clock after it is scaled which should be + * compensated in the next interrupt. + */ + lost_clock += current_irq_coalesced * s->period - + s->irq_coalesced * period; + DPRINTF_C("cmos: coalesced irqs scaled from %d to %d, %ld clocks " + "are compensated.\n", + current_irq_coalesced, s->irq_coalesced, lost_clock); } s->period = period; #endif @@ -170,7 +193,7 @@ static void periodic_timer_update(RTCState *s, int64_t current_time) cur_clock = muldiv64(current_time, RTC_CLOCK_RATE, NANOSECONDS_PER_SECOND); - next_irq_clock = (cur_clock & ~(period - 1)) + 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);