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Re: [Qemu-devel] [PATCH v3 4/9] mips: remove muldiv64()
From: |
Leon Alrae |
Subject: |
Re: [Qemu-devel] [PATCH v3 4/9] mips: remove muldiv64() |
Date: |
Tue, 8 Sep 2015 14:42:32 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 |
On 27/08/15 20:33, 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(), TIMER_FREQ)
>
> 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 MIPS timer frequency is 100 MHz, we can also do:
>
> y = x * 10; /* 100 MHz period is 10 ns */
>
> Signed-off-by: Laurent Vivier <address@hidden>
> ---
> hw/mips/cputimer.c | 19 ++++++++-----------
> 1 file changed, 8 insertions(+), 11 deletions(-)
Reviewed-by: Leon Alrae <address@hidden>