From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40549) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aQcl3-00023w-Hc for qemu-devel@nongnu.org; Tue, 02 Feb 2016 10:20:46 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aQckz-0002qW-J1 for qemu-devel@nongnu.org; Tue, 02 Feb 2016 10:20:45 -0500 References: <77d17ad13f7b20deb433ca7a7b3d7cf40429665e.1454169735.git.digetx@gmail.com> From: Dmitry Osipenko Message-ID: <56B0C90B.7000300@gmail.com> Date: Tue, 2 Feb 2016 18:19:39 +0300 MIME-Version: 1.0 In-Reply-To: <77d17ad13f7b20deb433ca7a7b3d7cf40429665e.1454169735.git.digetx@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] [PATCH v12 7/9] hw/ptimer: Fix counter - 1 returned by ptimer_get_count for the active timer List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: QEMU Developers , qemu-arm@nongnu.org Cc: Peter Maydell , Peter Crosthwaite 30.01.2016 19:43, Dmitry Osipenko пишет: > Due to rounding down performed by ptimer_get_count, it returns counter - 1 for > the active timer. That's incorrect because counter should decrement only after > period been expired, not before. I.e. if running timer has been loaded with > value X, then timer counter should stay with X until period expired and > decrement after. Fix this by adding 1 to the counter value for the active and > unexpired timer. > > Signed-off-by: Dmitry Osipenko > --- > hw/core/ptimer.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c > index 62f8cb1..b2044fb 100644 > --- a/hw/core/ptimer.c > +++ b/hw/core/ptimer.c > @@ -136,7 +136,7 @@ uint64_t ptimer_get_count(ptimer_state *s) > if ((uint32_t)(period_frac << shift)) > div += 1; > } > - counter = rem / div; > + counter = rem / div + (expired ? 0 : 1); > > if (expired && counter != 0) { > /* Wrap around periodic counter. */ > Noticed one nit here: There is possibility to return timer counter = limit + 1, if the following ptimer calls execute in less than 1ns. ptimer_run(t, 1); // counter = 91, if set() count executed in less than 1ns ptimer_set_count(t, 90); counter = ptimer_get_count(t); Likely, it would be impossible to trigger that issue on a real current machine. But the fix is trivial, I'll incorporate it in V13 if it looks fine: --- @@ -76,20 +76,20 @@ static void ptimer_tick(void *opaque) { ptimer_state *s = (ptimer_state *)opaque; s->delta = 0; ptimer_reload(s); } uint64_t ptimer_get_count(ptimer_state *s) { + int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL); uint64_t counter; - if (s->enabled && s->delta != 0) { - int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL); + if (s->enabled && s->delta != 0 && now != s->last_event) { int64_t next = s->next_event; bool expired = (now - next >= 0); bool oneshot = (s->enabled == 2); /* Figure out the current counter value. */ if (expired && (oneshot || use_icount)) { /* Prevent timer underflowing if it should already have triggered. */ @@ -131,17 +131,17 @@ uint64_t ptimer_get_count(ptimer_state *s) } else { if (shift != 0) div |= (period_frac >> (32 - shift)); /* Look at remaining bits of period_frac and round div up if necessary. */ if ((uint32_t)(period_frac << shift)) div += 1; } - counter = rem / div; + counter = rem / div + (expired ? 0 : 1); if (expired && counter != 0) { /* Wrap around periodic counter. */ counter = s->limit - (counter - 1) % s->limit; } } } else { counter = s->delta; -- Dmitry