From a548a4b5d3a130ada6498669b4bf01bf47fe4560 Mon Sep 17 00:00:00 2001 From: Richard Jones Date: Wed, 1 Nov 2017 11:33:02 +0100 Subject: [PATCH 7/7] i6300esb: remove muldiv64() RH-Author: Richard Jones Message-id: <1509535982-27927-4-git-send-email-rjones@redhat.com> Patchwork-id: 77463 O-Subject: [RHEL-7.5 qemu-kvm PATCH v3 3/3] i6300esb: remove muldiv64() Bugzilla: 1470244 RH-Acked-by: Paolo Bonzini RH-Acked-by: Thomas Huth RH-Acked-by: Miroslav Rezanina From: Laurent Vivier 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 (cherry picked from commit 9491e9bc019a365dfa9780f462984a0d052f4c0d) BZ: https://bugzilla.redhat.com/show_bug.cgi?id=1470244 Upstream-status: 9491e9bc019a365dfa9780f462984a0d052f4c0d Signed-off-by: Miroslav Rezanina --- 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 fa8e3b9..6dede4e 100644 --- a/hw/watchdog/wdt_i6300esb.c +++ b/hw/watchdog/wdt_i6300esb.c @@ -125,14 +125,9 @@ 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); -- 1.8.3.1