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mac_via: fix 60Hz VIA1 timer interval

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The 60Hz timer is initialised using timer_new_ns() meaning that the timer
interval should be measured in ns, and therefore its period is a thousand
times too short.

Use a define for the 60Hz timer period taking the more precise value as
documented in the Guide To The Macintosh Family Hardware.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: BALATON Zoltan <balaton@eik.bme.hu>
Message-Id: <20210311100505.22596-7-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
This commit is contained in:
Mark Cave-Ayland 2021-03-11 10:05:04 +00:00 committed by Laurent Vivier
parent 4c8f4ab41c
commit 82ff856fe7
1 changed files with 9 additions and 2 deletions
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11
hw/misc/mac_via.c
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@ -279,6 +279,12 @@
#define VIA_TIMER_FREQ (783360)
#define VIA_ADB_POLL_FREQ 50 /* XXX: not real */
/*
* Guide to the Macintosh Family Hardware ch. 12 "Displays" p. 401 gives the
* precise 60Hz interrupt frequency as ~60.15Hz with a period of 16625.8 us
*/
#define VIA_60HZ_TIMER_PERIOD_NS 16625800
/* VIA returns time offset from Jan 1, 1904, not 1970 */
#define RTC_OFFSET 2082844800
@ -302,8 +308,9 @@ static void via1_sixty_hz_update(MOS6522Q800VIA1State *v1s)
MOS6522State *s = MOS6522(v1s);
/* 60 Hz irq */
v1s->next_sixty_hz = (qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + 16630) /
16630 * 16630;
v1s->next_sixty_hz = (qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +
VIA_60HZ_TIMER_PERIOD_NS) /
VIA_60HZ_TIMER_PERIOD_NS * VIA_60HZ_TIMER_PERIOD_NS;
if (s->ier & VIA1_IRQ_60HZ) {
timer_mod(v1s->sixty_hz_timer, v1s->next_sixty_hz);