Re: [PATCH 1/3] sched_clock: Round the frequency reported to nearest rather than down

[John Stultz]

On Sun, Apr 24, 2022 at 4:47 AM Maciej W. Rozycki <macro@xxxxxxxxxxx> wrote:
>
> We currently round the frequency reported for clock sources down, which
> gives misleading figures, e.g.:
>
> I/O ASIC clock frequency 24999480Hz
> clocksource: dec-ioasic: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 76452008078 ns
> sched_clock: 32 bits at 24MHz, resolution 40ns, wraps every 85901132779ns
> MIPS counter frequency 59998512Hz
> clocksource: MIPS: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 31855130776 ns
> sched_clock: 32 bits at 59MHz, resolution 16ns, wraps every 35792281591ns
>
> Rounding to nearest seems more adequate:
>
> I/O ASIC clock frequency 24999664Hz
> clocksource: dec-ioasic: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 76451445358 ns
> sched_clock: 32 bits at 25MHz, resolution 40ns, wraps every 85900499947ns
> MIPS counter frequency 59999728Hz
> clocksource: MIPS: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 31854485176 ns
> sched_clock: 32 bits at 60MHz, resolution 16ns, wraps every 35791556599ns
>
> Signed-off-by: Maciej W. Rozycki <macro@xxxxxxxxxxx>
> Fixes: 112f38a4a316 ("ARM: sched_clock: provide common infrastructure for sched_clock()")
> ---

This seems sane to me.

Acked-by: John Stultz <jstultz@xxxxxxxxxx>

thanks
-john