From: Laurent Vivier <lvivier@redhat.com>
To: qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>,
"Michael S . Tsirkin" <mst@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>
Subject: [Qemu-devel] [PATCH v3 3/9] pcnet: remove muldiv64()
Date: Thu, 27 Aug 2015 21:33:01 +0200 [thread overview]
Message-ID: <1440703987-29012-4-git-send-email-lvivier@redhat.com> (raw)
In-Reply-To: <1440703987-29012-1-git-send-email-lvivier@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 <lvivier@redhat.com>
---
v3: part of "PCI: remove muldiv64()"
hw/net/pcnet.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/hw/net/pcnet.c b/hw/net/pcnet.c
index 3437376..0eb3cc4 100644
--- a/hw/net/pcnet.c
+++ b/hw/net/pcnet.c
@@ -670,8 +670,7 @@ static inline hwaddr pcnet_rdra_addr(PCNetState *s, int idx)
static inline int64_t pcnet_get_next_poll_time(PCNetState *s, int64_t current_time)
{
int64_t next_time = current_time +
- muldiv64(65536 - (CSR_SPND(s) ? 0 : CSR_POLL(s)),
- get_ticks_per_sec(), 33000000L);
+ (65536 - (CSR_SPND(s) ? 0 : CSR_POLL(s))) * 30;
if (next_time <= current_time)
next_time = current_time + 1;
return next_time;
--
2.1.0
next prev parent reply other threads:[~2015-08-27 19:33 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 ` Laurent Vivier [this message]
2015-08-28 14:12 ` [Qemu-devel] [PATCH v3 3/9] pcnet: " Stefan Hajnoczi
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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