From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59033) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZMGiz-0001nc-L6 for qemu-devel@nongnu.org; Mon, 03 Aug 2015 10:28:22 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZMGiv-00078T-Fp for qemu-devel@nongnu.org; Mon, 03 Aug 2015 10:28:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36415) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZMGiv-00078P-BE for qemu-devel@nongnu.org; Mon, 03 Aug 2015 10:28:17 -0400 References: <1438609948-3744-1-git-send-email-lvivier@redhat.com> From: Laurent Vivier Message-ID: <55BF7A7E.1050303@redhat.com> Date: Mon, 3 Aug 2015 16:28:14 +0200 MIME-Version: 1.0 In-Reply-To: <1438609948-3744-1-git-send-email-lvivier@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] i6300esb: correctly convert watchdog clock ticks into nanoseconds List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Paolo Bonzini , "Richard W.M. Jones" , David Gibson On 03/08/2015 15:52, Laurent Vivier wrote: > Originally, qemu_mod_timer() was using ticks to count time. > And i6300esb was converting internal clock ticks (33 MHz) to > QEMU timer ticks. > > The timer has been changed by a script to use nanoseconds: > > 7447545 change all other clock references to use > nanosecond resolution accessors > > As i6300esb takes nanoseconds, we don't need anymore to > multiply counter by get_ticks_per_sec()/33MHz, but instead > we must convert watchdog ticks into nanoseconds. > > Signed-off-by: Laurent Vivier > --- > hw/watchdog/wdt_i6300esb.c | 25 +++++++++++++++---------- > 1 file changed, 15 insertions(+), 10 deletions(-) > > diff --git a/hw/watchdog/wdt_i6300esb.c b/hw/watchdog/wdt_i6300esb.c > index cfa2b1b..21119ab 100644 > --- a/hw/watchdog/wdt_i6300esb.c > +++ b/hw/watchdog/wdt_i6300esb.c > @@ -124,19 +124,24 @@ static void i6300esb_restart_timer(I6300State *d, int stage) > else > timeout = d->timer2_preload; > > - if (d->clock_scale == CLOCK_SCALE_1KHZ) > + /* convert timeout to 33Mhz clock ticks */ > + if (d->clock_scale == CLOCK_SCALE_1KHZ) { > + /* The 20-bit Preload Value is loaded into bits 34:15 of the > + * main down counter. [...] The approximate clock generated > + * is 1 KHz, (Default) > + */ > timeout <<= 15; > - else > + } else { > + /* The 20-bit Preload Value is loaded into bits 24:5 of the > + * main down counter. [...] The approximate clock generated > + * is 1 MHz. > + */ > timeout <<= 5; > - > - /* Get the timeout in units of ticks_per_sec. > - * > - * ticks_per_sec is typically 10^9 == 0x3B9ACA00 (30 bits), with > - * 20 bits of user supplied preload, and 15 bits of scale, the > - * multiply here can exceed 64-bits, before we divide by 33MHz, so > - * we use a higher-precision intermediate result. > + } > + /* A 33 Mhz clock gives a 30 ns tick, > + * convert timeout from ticks to ns > */ > - timeout = muldiv64(get_ticks_per_sec(), timeout, 33000000); > + timeout *= 30; I'm wondering if a 33 Mhz clock is 33000000 Hz or 33333333 Hz ? if this is the former, I should use "timeout = timeout * 1000 / 33" instead. (35 bit value * 10 bit value = 45 bit value, it fits in a 64 bit integer) Any comment ? > > i6300esb_debug("stage %d, timeout %" PRIi64 "\n", d->stage, timeout); > >