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Re: [PATCH 6/7] mac_via: fix 60Hz VIA1 timer interval
From: |
Philippe Mathieu-Daudé |
Subject: |
Re: [PATCH 6/7] mac_via: fix 60Hz VIA1 timer interval |
Date: |
Wed, 10 Mar 2021 14:27:42 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 |
On 3/10/21 2:10 PM, Laurent Vivier wrote:
> Le 10/03/2021 à 13:56, Laurent Vivier a écrit :
>> Le 10/03/2021 à 13:32, BALATON Zoltan a écrit :
>>> On Wed, 10 Mar 2021, Mark Cave-Ayland wrote:
>>>> 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.
>>>>
>>>> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
>>>> ---
>>>> hw/misc/mac_via.c | 4 ++--
>>>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/hw/misc/mac_via.c b/hw/misc/mac_via.c
>>>> index f994fefa7c..c6e1552a59 100644
>>>> --- a/hw/misc/mac_via.c
>>>> +++ b/hw/misc/mac_via.c
>>>> @@ -302,8 +302,8 @@ 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) +
>>>> 16630000) /
>>>> + 16630000 * 16630000;
>>>
>>> Can you put this magic number in a #define maybe also rewriting it in a way
>>> that shows it
>>> corresponds to a 60 Hz interval. (There's NANOSECONDS_PER_SECOND defined in
>>> include/qemu/timer.h
>>> that could be used for that, there's also SCALE_MS that might replace 1000
>>> * 1000 elsewhere in this
>>> file). Also NANOSECONDS_PER_SECOND / 60 is 16666666, should that value be
>>> used here instead?
>>
>> In fact, the Mac Frequency is not exactly 60 Hz, in docs we can find 60.147
>> Hz, in kernel 60.15 Hz.
>> I Think there are several ways to compute it...
Good candidate to switch to the Clock API, see docs/devel/clocks.rst
once this gets merged:
https://www.mail-archive.com/qemu-devel@nongnu.org/msg788864.html
> In fact, we can read:
>
> "the vertical retrace frequency is approximately 60.15 Hz, resulting in a
> period of approximately
> 16.63 milliseconds"
>
> https://developer.apple.com/library/archive/documentation/mac/pdf/Processes/Vertical_Retrace_Mgr.pdf
>
> Thanks,
> Laurent
>
>
- Re: [PATCH 6/7] mac_via: fix 60Hz VIA1 timer interval, (continued)
- Re: [PATCH 6/7] mac_via: fix 60Hz VIA1 timer interval, Laurent Vivier, 2021/03/10
- Re: [PATCH 6/7] mac_via: fix 60Hz VIA1 timer interval, BALATON Zoltan, 2021/03/10
- Re: [PATCH 6/7] mac_via: fix 60Hz VIA1 timer interval, Laurent Vivier, 2021/03/10
- Re: [PATCH 6/7] mac_via: fix 60Hz VIA1 timer interval, Laurent Vivier, 2021/03/10
- Re: [PATCH 6/7] mac_via: fix 60Hz VIA1 timer interval, Laurent Vivier, 2021/03/10
- Re: [PATCH 6/7] mac_via: fix 60Hz VIA1 timer interval, Mark Cave-Ayland, 2021/03/10
- Re: [PATCH 6/7] mac_via: fix 60Hz VIA1 timer interval, BALATON Zoltan, 2021/03/10
- Re: [PATCH 6/7] mac_via: fix 60Hz VIA1 timer interval, Mark Cave-Ayland, 2021/03/11
- Re: [PATCH 6/7] mac_via: fix 60Hz VIA1 timer interval, Laurent Vivier, 2021/03/11
- Re: [PATCH 6/7] mac_via: fix 60Hz VIA1 timer interval, Mark Cave-Ayland, 2021/03/11
- Re: [PATCH 6/7] mac_via: fix 60Hz VIA1 timer interval,
Philippe Mathieu-Daudé <=
[PATCH 7/7] mac_via: remove VIA1 timer optimisations, Mark Cave-Ayland, 2021/03/10