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

[Philippe Mathieu-Daudé]

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? 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;
> +    }