Re: [PATCH] x86/lguest/timer: set ->min_delta_ticks and ->max_delta_ticks

Rusty Russell
2017-04-02T23:42:12Z

Nicolai Stange <nicstange@gmail.com> writes:
> In preparation for making the clockevents core NTP correction aware,
> all clockevent device drivers must set ->min_delta_ticks and
> ->max_delta_ticks rather than ->min_delta_ns and ->max_delta_ns: a
> clockevent device's rate is going to change dynamically and thus, the
> ratio of ns to ticks ceases to stay invariant.
>
> Make the x86 arch's lguest clockevent driver initialize these fields
> properly.
>
> This patch alone doesn't introduce any change in functionality as the
> clockevents core still looks exclusively at the (untouched) ->min_delta_ns
> and ->max_delta_ns. As soon as this has changed, a followup patch will
> purge the initialization of ->min_delta_ns and ->max_delta_ns from this
> driver.

Acked-by: Rusty Russell <rusty@rustcorp.com.au>

>
> Signed-off-by: Nicolai Stange <nicstange@gmail.com>
> ---
>
> Notes:
> This prerequisite patch is part of a larger effort to feed NTP
> corrections into the clockevent devices' frequencies and thus
> avoiding their notion of time to diverge from the system's
> one. If you're interested, the current state of the whole series
> can be found at [1].
>
> If you haven't got any objections and these prerequisites get
> merged by 4.12 everywhere, I'll proceed with the remainder of
> this series in 4.13.
>
> Applicable to next-20170324 as well as to John' Stultz tree [2].
>
> [1]
> git://nicst.de/linux.git cev-freq-adj.v10.fortglx-4.12-time
> https://nicst.de/git/?p=linux.git;a=shortlog;h=refs/heads/cev-freq-adj.v10.fortglx-4.12-time
>
> [2]
> https://git.linaro.org/people/john.stultz/linux.git fortglx/4.12/time
>
> arch/x86/lguest/boot.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
> index d3289d7e78fa..3e4bf887a246 100644
> --- a/arch/x86/lguest/boot.c
> +++ b/arch/x86/lguest/boot.c
> @@ -994,7 +994,9 @@ static struct clock_event_device lguest_clockevent = {
> .mult = 1,
> .shift = 0,
> .min_delta_ns = LG_CLOCK_MIN_DELTA,
> + .min_delta_ticks = LG_CLOCK_MIN_DELTA,
> .max_delta_ns = LG_CLOCK_MAX_DELTA,
> + .max_delta_ticks = LG_CLOCK_MAX_DELTA,
> };
>
> /*
> --
> 2.12.0