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[Qemu-devel] [PATCH v3 3/9] pcnet: remove muldiv64()
From: |
Laurent Vivier |
Subject: |
[Qemu-devel] [PATCH v3 3/9] pcnet: remove muldiv64() |
Date: |
Thu, 27 Aug 2015 21:33:01 +0200 |
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 <address@hidden>
---
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
- [Qemu-devel] [PATCH v3 0/9] remove useless muldiv64(), Laurent Vivier, 2015/08/27
- [Qemu-devel] [PATCH v3 1/9] i6300esb: remove muldiv64(), Laurent Vivier, 2015/08/27
- [Qemu-devel] [PATCH v3 2/9] rtl8139: remove muldiv64(), Laurent Vivier, 2015/08/27
- [Qemu-devel] [PATCH v3 3/9] pcnet: remove muldiv64(),
Laurent Vivier <=
- [Qemu-devel] [PATCH v3 4/9] mips: remove muldiv64(), Laurent Vivier, 2015/08/27
- [Qemu-devel] [PATCH v3 5/9] openrisc: remove muldiv64(), Laurent Vivier, 2015/08/27
- [Qemu-devel] [PATCH v3 6/9] arm: clarify the use of muldiv64(), Laurent Vivier, 2015/08/27
- [Qemu-devel] [PATCH v3 7/9] hpet: remove muldiv64(), Laurent Vivier, 2015/08/27
- [Qemu-devel] [PATCH v3 8/9] bt: remove muldiv64(), Laurent Vivier, 2015/08/27
- [Qemu-devel] [PATCH v3 9/9] net: remove muldiv64(), Laurent Vivier, 2015/08/27