Re: [PATCH] x86/xen/time: set ->min_delta_ticks and ->max_delta_ticks

Juergen Gross
2017-04-06T09:12:02Z

On 30/03/17 22:06, Nicolai Stange wrote:
> 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 xen 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.
>
> Signed-off-by: Nicolai Stange <nicstange@gmail.com>

Shall I carry this patch through the Xen tree or will it be processed
via the tip tree? I'm fine with both variants.

Juergen

> ---
>
> 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/xen/time.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
> index 1e69956d7852..7a3089285c59 100644
> --- a/arch/x86/xen/time.c
> +++ b/arch/x86/xen/time.c
> @@ -209,7 +209,9 @@ static const struct clock_event_device xen_timerop_clockevent = {
> .features = CLOCK_EVT_FEAT_ONESHOT,
>
> .max_delta_ns = 0xffffffff,
> + .max_delta_ticks = 0xffffffff,
> .min_delta_ns = TIMER_SLOP,
> + .min_delta_ticks = TIMER_SLOP,
>
> .mult = 1,
> .shift = 0,
> @@ -268,7 +270,9 @@ static const struct clock_event_device xen_vcpuop_clockevent = {
> .features = CLOCK_EVT_FEAT_ONESHOT,
>
> .max_delta_ns = 0xffffffff,
> + .max_delta_ticks = 0xffffffff,
> .min_delta_ns = TIMER_SLOP,
> + .min_delta_ticks = TIMER_SLOP,
>
> .mult = 1,
> .shift = 0,
>