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From: Dmitry Osipenko <digetx@gmail.com>
Message-ID: <569FC243.6090507@gmail.com>
Date: Wed, 20 Jan 2016 20:22:11 +0300
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Subject: Re: [Qemu-devel] [PATCH v10 2/7] hw/ptimer: Perform tick and
 counter wrap around if timer already expired
To: Peter Crosthwaite <crosthwaitepeter@gmail.com>
Cc: Peter Maydell <peter.maydell@linaro.org>, qemu-arm <qemu-arm@nongnu.org>, QEMU Developers <qemu-devel@nongnu.org>

20.01.2016 20:03, Dmitry Osipenko пишет:
> Hi Peter,
>
> 10.01.2016 03:44, Peter Crosthwaite пишет:
>> On Sat, Jan 9, 2016 at 9:39 AM, Dmitry Osipenko <digetx@gmail.com> wrote:
> [cut]
>>> In addition, there is no reason to keep expired timer tick deferred, so
>>> just perform the tick from ptimer_get_count().
>>>
> [cut]
>
> I noticed an issue here... The problem is that device reset invokes
> ptimer_stop() that invokes ptimer_get_count() that might cause the tick after
> reset, i.e. bogus bh would be invoked after QEMU reset. I have reproduced that
> issue.
>
> The solution might be to introduce ptimer_reset() that would stop QEMU timer and
> reset delta/load/period without invoking ptimer_get_count. And of course all
> devices should be updated to use new ptimer_reset() prior to "Perform tick and
> counter wrap around if timer already expired" patch, but that's not an issue I
> suppose. Please let me know if you have any objections, I'm leaning to do it in
> V11.
>
> void ptimer_reset(ptimer_state *s)
> {
>      timer_del(s->timer);
>      s->enabled = 0;
>      s->period_frac = 0;
>      s->period = 0;
>      s->delta = 0;
>      s->limit = 0;
> }
>

However, ptimer_stop() still would be broken. So maybe it's better to keep tick 
deferred.

-- 
Dmitry