From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46138) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZbTrO-0004kM-Rp for qemu-devel@nongnu.org; Mon, 14 Sep 2015 09:31:55 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZbTrK-0003Tm-RS for qemu-devel@nongnu.org; Mon, 14 Sep 2015 09:31:54 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51245) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZbTrK-0003TJ-Kn for qemu-devel@nongnu.org; Mon, 14 Sep 2015 09:31:50 -0400 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (Postfix) with ESMTPS id C2820A2A1A for ; Mon, 14 Sep 2015 13:31:49 +0000 (UTC) From: Laurent Vivier Date: Mon, 14 Sep 2015 15:31:42 +0200 Message-Id: <1442237502-21427-1-git-send-email-lvivier@redhat.com> In-Reply-To: <1440703987-29012-2-git-send-email-lvivier@redhat.com> References: <1440703987-29012-2-git-send-email-lvivier@redhat.com> Subject: [Qemu-devel] [PATCH v4 1/9] i6300esb: remove muldiv64() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Laurent Vivier , pbonzini@redhat.com, stefanha@redhat.com, mst@redhat.com 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 --- v4: only rebase this patch on origin/master as the line is modified by commit "fee562e i6300esb: fix timer overflow" 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); -- 2.1.0