Re: [RFC 09/10] hw/mos6522: Avoid using discrepant QEMU clock values

[Finn Thain <fthain@linux-m68k.org>]

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On Tue, 24 Aug 2021, Philippe Mathieu-Daudé wrote:

> On 8/24/21 12:09 PM, Finn Thain wrote:
> > mos6522_read() and mos6522_write() may call various functions to determine
> > timer irq state, timer counter value and QEMUTimer deadline. All called
> > functions must use the same value for the present time.
> > 
> > Signed-off-by: Finn Thain <fthain@linux-m68k.org>
> > ---
> >  hw/misc/mos6522.c | 51 +++++++++++++++++++++++++----------------------
> >  1 file changed, 27 insertions(+), 24 deletions(-)
> 
> > @@ -123,20 +123,19 @@ static int64_t get_next_irq_time(MOS6522State *s, MOS6522Timer *ti,
> >      trace_mos6522_get_next_irq_time(ti->latch, d, next_time - d);
> >      next_time = muldiv64(next_time, NANOSECONDS_PER_SECOND, ti->frequency) +
> >                           ti->load_time;
> > -
> > -    if (next_time <= current_time) {
> > -        next_time = current_time + 1;
> > -    }
> 
> Maybe extract as an helper? 

There is a small amount of code duplication here but it gets resolved in 
patch 10/10.

> Otherwise:
> 
> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> 
> >      return next_time;
> >  }
> >  
> >  static void mos6522_timer1_update(MOS6522State *s, MOS6522Timer *ti,
> > -                                 int64_t current_time)
> > +                                  int64_t now)
> >  {
> >      if (!ti->timer) {
> >          return;
> >      }
> > -    ti->next_irq_time = get_next_irq_time(s, ti, current_time);
> > +    ti->next_irq_time = get_next_irq_time(s, ti, now);
> > +    if (ti->next_irq_time <= now) {
> > +        ti->next_irq_time = now + 1;
> > +    }
> >      if ((s->ier & T1_INT) == 0 ||
> >          ((s->acr & T1MODE) == T1MODE_ONESHOT && ti->oneshot_fired)) {
> >          timer_del(ti->timer);
> > @@ -146,12 +145,15 @@ static void mos6522_timer1_update(MOS6522State *s, MOS6522Timer *ti,
> >  }
> >  
> >  static void mos6522_timer2_update(MOS6522State *s, MOS6522Timer *ti,
> > -                                 int64_t current_time)
> > +                                  int64_t now)
> >  {
> >      if (!ti->timer) {
> >          return;
> >      }
> > -    ti->next_irq_time = get_next_irq_time(s, ti, current_time);
> > +    ti->next_irq_time = get_next_irq_time(s, ti, now);
> > +    if (ti->next_irq_time <= now) {
> > +        ti->next_irq_time = now + 1;
> > +    }
> 
>