From: Stefan Hajnoczi <stefanha@redhat.com>
To: Laurent Vivier <lvivier@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
qemu-devel@nongnu.org, "Michael S . Tsirkin" <mst@redhat.com>
Subject: Re: [Qemu-devel] [PATCH v3 3/9] pcnet: remove muldiv64()
Date: Fri, 28 Aug 2015 15:12:59 +0100 [thread overview]
Message-ID: <20150828141259.GE30542@stefanha-thinkpad.redhat.com> (raw)
In-Reply-To: <1440703987-29012-4-git-send-email-lvivier@redhat.com>
On Thu, Aug 27, 2015 at 09:33:01PM +0200, Laurent Vivier wrote:
> 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 <lvivier@redhat.com>
> ---
> v3: part of "PCI: remove muldiv64()"
> hw/net/pcnet.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
next prev parent reply other threads:[~2015-08-28 14:13 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-27 19:32 [Qemu-devel] [PATCH v3 0/9] remove useless muldiv64() Laurent Vivier
2015-08-27 19:32 ` [Qemu-devel] [PATCH v3 1/9] i6300esb: remove muldiv64() Laurent Vivier
2015-09-14 13:31 ` [Qemu-devel] [PATCH v4 " Laurent Vivier
2015-08-27 19:33 ` [Qemu-devel] [PATCH v3 2/9] rtl8139: " Laurent Vivier
2015-08-28 14:12 ` Stefan Hajnoczi
2015-08-27 19:33 ` [Qemu-devel] [PATCH v3 3/9] pcnet: " Laurent Vivier
2015-08-28 14:12 ` Stefan Hajnoczi [this message]
2015-08-27 19:33 ` [Qemu-devel] [PATCH v3 4/9] mips: " Laurent Vivier
2015-09-08 12:54 ` Laurent Vivier
2015-09-08 13:42 ` Leon Alrae
2015-08-27 19:33 ` [Qemu-devel] [PATCH v3 5/9] openrisc: " Laurent Vivier
2015-09-08 12:54 ` Laurent Vivier
2015-08-27 19:33 ` [Qemu-devel] [PATCH v3 6/9] arm: clarify the use of muldiv64() Laurent Vivier
2015-08-27 20:23 ` Peter Crosthwaite
2015-09-01 11:17 ` Peter Maydell
2015-09-01 11:23 ` Laurent Vivier
2015-09-01 11:30 ` Peter Maydell
2015-08-27 19:33 ` [Qemu-devel] [PATCH v3 7/9] hpet: remove muldiv64() Laurent Vivier
2015-09-08 12:55 ` Laurent Vivier
2015-09-08 12:58 ` Paolo Bonzini
2015-08-27 19:33 ` [Qemu-devel] [PATCH v3 8/9] bt: " Laurent Vivier
2015-09-08 12:55 ` Laurent Vivier
2015-09-08 12:57 ` Paolo Bonzini
2015-08-27 19:33 ` [Qemu-devel] [PATCH v3 9/9] net: " Laurent Vivier
2015-08-28 14:12 ` Stefan Hajnoczi
2015-09-24 16:21 ` [Qemu-devel] [PATCH v3 0/9] remove useless muldiv64() Laurent Vivier
2015-09-25 10:31 ` Paolo Bonzini
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