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Re: [Qemu-devel] [PATCH v10 2/7] hw/ptimer: Perform tick and counter wra

From: Dmitry Osipenko
Subject: Re: [Qemu-devel] [PATCH v10 2/7] hw/ptimer: Perform tick and counter wrap around if timer already expired
Date: Wed, 20 Jan 2016 20:22:11 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0

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 <address@hidden> wrote:
In addition, there is no reason to keep expired timer tick deferred, so
just perform the tick from ptimer_get_count().


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

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

void ptimer_reset(ptimer_state *s)
     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.


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