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Re: [Qemu-devel] [PATCH v3 2/9] rtl8139: remove muldiv64()
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH v3 2/9] rtl8139: remove muldiv64() |
Date: |
Fri, 28 Aug 2015 15:12:55 +0100 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Thu, Aug 27, 2015 at 09:33:00PM +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 <address@hidden>
> ---
> v3: part of "PCI: remove muldiv64()"
> hw/net/rtl8139.c | 14 ++++++--------
> tests/rtl8139-test.c | 2 +-
> 2 files changed, 7 insertions(+), 9 deletions(-)
Reviewed-by: Stefan Hajnoczi <address@hidden>
- [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
- Re: [Qemu-devel] [PATCH v3 2/9] rtl8139: remove muldiv64(),
Stefan Hajnoczi <=
- [Qemu-devel] [PATCH v3 3/9] pcnet: remove muldiv64(), Laurent Vivier, 2015/08/27
- [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