From patchwork Fri Sep 25 14:09:02 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Laurent Vivier X-Patchwork-Id: 522856 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 1A9D114090A for ; Sat, 26 Sep 2015 00:35:38 +1000 (AEST) Received: from localhost ([::1]:43118 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZfU63-0007qb-R6 for incoming@patchwork.ozlabs.org; Fri, 25 Sep 2015 10:35:35 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43287) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZfTgj-0006xM-HJ for qemu-devel@nongnu.org; Fri, 25 Sep 2015 10:09:26 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZfTgd-0007Bq-NZ for qemu-devel@nongnu.org; Fri, 25 Sep 2015 10:09:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45175) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZfTgd-0007Bc-Ip for qemu-devel@nongnu.org; Fri, 25 Sep 2015 10:09:19 -0400 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (Postfix) with ESMTPS id 344A8461C3 for ; Fri, 25 Sep 2015 14:09:19 +0000 (UTC) Received: from thinkpad.redhat.com (vpn1-4-166.ams2.redhat.com [10.36.4.166]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t8PE9Gx4019470; Fri, 25 Sep 2015 10:09:18 -0400 From: Laurent Vivier To: pbonzini@redhat.com Date: Fri, 25 Sep 2015 16:09:02 +0200 Message-Id: <1443190150-17312-2-git-send-email-lvivier@redhat.com> In-Reply-To: <1443190150-17312-1-git-send-email-lvivier@redhat.com> References: <1443190150-17312-1-git-send-email-lvivier@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.23 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: Laurent Vivier , qemu-devel@nongnu.org Subject: [Qemu-devel] [PULL 1/9] i6300esb: remove muldiv64() X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Originally, timers were ticks based, and it made sense to add ticks to current time to know when to trigger an alarm. But since commit: 7447545 change all other clock references to use nanosecond resolution accessors All timers use nanoseconds and we need to convert ticks to nanoseconds, by doing something like: y = muldiv64(x, get_ticks_per_sec(), PCI_FREQUENCY) where x is the number of device ticks and y the number of system ticks. y is used as nanoseconds in timer functions, it works because 1 tick is 1 nanosecond. (get_ticks_per_sec() is 10^9) But as PCI frequency is 33 MHz, we can also do: y = x * 30; /* 33 MHz PCI period is 30 ns */ Which is much more simple. This implies a 33.333333 MHz PCI frequency, but this is correct. Signed-off-by: Laurent Vivier --- hw/watchdog/wdt_i6300esb.c | 11 +++-------- 1 file changed, 3 insertions(+), 8 deletions(-) diff --git a/hw/watchdog/wdt_i6300esb.c b/hw/watchdog/wdt_i6300esb.c index 3e07d44..a91c8fd 100644 --- a/hw/watchdog/wdt_i6300esb.c +++ b/hw/watchdog/wdt_i6300esb.c @@ -129,14 +129,9 @@ static void i6300esb_restart_timer(I6300State *d, int stage) else 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. - */ - timeout = muldiv64(timeout, get_ticks_per_sec(), 33000000); + /* Get the timeout in nanoseconds. */ + + timeout = timeout * 30; /* on a PCI bus, 1 tick is 30 ns*/ i6300esb_debug("stage %d, timeout %" PRIi64 "\n", d->stage, timeout);