On 05/03/2017 11:39 PM, Paolo Bonzini wrote:
On 12/04/2017 11:51, guangrong.xiao@xxxxxxxxx wrote:
From: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxx>
Move the x86 specific code in periodic_timer_update() to a common place,
the actual logic is not changed
Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxx>
---
hw/timer/mc146818rtc.c | 112 +++++++++++++++++++++++++++++--------------------
1 file changed, 66 insertions(+), 46 deletions(-)
diff --git a/hw/timer/mc146818rtc.c b/hw/timer/mc146818rtc.c
index 3bf559d..d7b7c56 100644
--- a/hw/timer/mc146818rtc.c
+++ b/hw/timer/mc146818rtc.c
@@ -144,6 +144,63 @@ static void rtc_coalesced_timer(void *opaque)
rtc_coalesced_timer_update(s);
}
+
+static int64_t
+arch_periodic_timer_update(RTCState *s, int period, int64_t lost_clock)
+{
+ if (period != s->period) {
+ int64_t scale_lost_clock;
+ 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.
+ */
+ scale_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, scale_lost_clock);
+ lost_clock += scale_lost_clock;
+ s->period = period;
This should be moved up to the caller.
It should not. As you pointed out below, all these code are only needed
for LOST_TICK_POLICY_SLEW that is x86 specific.
Or use "if (s->lost_tick_policy != LOST_TICK_POLICY_SLEW)" without
"#ifdef TARGET_I386" is acceptable as only x86 can make it SLEW,
Unnecessary branch checks will little slow down other architectures,
but i think it is acceptable, right? :)
Also, if s->lost_tick_policy is not SLEW, s->irq_coalesced on input is
zero. So I *think* what you get is equivalent to
if (s->lost_tick_policy != LOST_TICK_POLICY_SLEW) {
return;
}
/* ... comment ... */
lost_interrupt = (s->irq_coalesced * s->period) / period;
lost_clock += (s->irq_coalesced * s->period) % period;
lost_interrupt += lost_clock / period;
lost_clock %= period;
s->irq_coalesced = load_interrupt;
rtc_coalesced_timer_update(s);
or equivalently:
lost_clock += s->irq_coalesced * s->period;
s->irq_coalesced = lost_clock / period;
lost_clock %= period;
rtc_coalesced_timer_update(s);
Exactly right, it is much better, will apply it.
I think you should probably merge these three patches and document the
resulting logic, because it's simpler than building it a patch at a time.
Okay, i will consider it carefully in the next version.
Thank you, Paolo!
