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From a548a4b5d3a130ada6498669b4bf01bf47fe4560 Mon Sep 17 00:00:00 2001
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From: Richard Jones <rjones@redhat.com>
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Date: Wed, 1 Nov 2017 11:33:02 +0100
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Subject: [PATCH 7/7] i6300esb: remove muldiv64()
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RH-Author: Richard Jones <rjones@redhat.com>
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Message-id: <1509535982-27927-4-git-send-email-rjones@redhat.com>
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Patchwork-id: 77463
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O-Subject: [RHEL-7.5 qemu-kvm PATCH v3 3/3] i6300esb: remove muldiv64()
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Bugzilla: 1470244
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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RH-Acked-by: Thomas Huth <thuth@redhat.com>
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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From: Laurent Vivier <lvivier@redhat.com>
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Originally, timers were ticks based, and it made sense to
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add ticks to current time to know when to trigger an alarm.
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But since commit:
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7447545 change all other clock references to use nanosecond resolution accessors
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All timers use nanoseconds and we need to convert ticks to nanoseconds, by
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doing something like:
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y = muldiv64(x, get_ticks_per_sec(), PCI_FREQUENCY)
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where x is the number of device ticks and y the number of system ticks.
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y is used as nanoseconds in timer functions,
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it works because 1 tick is 1 nanosecond.
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(get_ticks_per_sec() is 10^9)
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But as PCI frequency is 33 MHz, we can also do:
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y = x * 30; /* 33 MHz PCI period is 30 ns */
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Which is much more simple.
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This implies a 33.333333 MHz PCI frequency,
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but this is correct.
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Signed-off-by: Laurent Vivier <lvivier@redhat.com>
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(cherry picked from commit 9491e9bc019a365dfa9780f462984a0d052f4c0d)
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BZ: https://bugzilla.redhat.com/show_bug.cgi?id=1470244
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Upstream-status: 9491e9bc019a365dfa9780f462984a0d052f4c0d
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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hw/watchdog/wdt_i6300esb.c | 11 +++--------
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1 file changed, 3 insertions(+), 8 deletions(-)
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diff --git a/hw/watchdog/wdt_i6300esb.c b/hw/watchdog/wdt_i6300esb.c
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index fa8e3b9..6dede4e 100644
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--- a/hw/watchdog/wdt_i6300esb.c
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+++ b/hw/watchdog/wdt_i6300esb.c
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@@ -125,14 +125,9 @@ static void i6300esb_restart_timer(I6300State *d, int stage)
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else
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timeout <<= 5;
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- /* Get the timeout in units of ticks_per_sec.
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- *
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- * ticks_per_sec is typically 10^9 == 0x3B9ACA00 (30 bits), with
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- * 20 bits of user supplied preload, and 15 bits of scale, the
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- * multiply here can exceed 64-bits, before we divide by 33MHz, so
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- * we use a higher-precision intermediate result.
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- */
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- timeout = muldiv64(timeout, get_ticks_per_sec(), 33000000);
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+ /* Get the timeout in nanoseconds. */
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+
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+ timeout = timeout * 30; /* on a PCI bus, 1 tick is 30 ns*/
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i6300esb_debug("stage %d, timeout %" PRIi64 "\n", d->stage, timeout);
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--
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1.8.3.1
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