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Subject[PATCH] x86/apic/timer: set ->min_delta_ticks and ->max_delta_ticks
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 apic clockevent driver initialize these fields

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

Signed-off-by: Nicolai Stange <>

(First test sending for 23 similar patches in different subsystems
to follow.)

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].

git:// cev-freq-adj.v10.fortglx-4.12-time;a=shortlog;h=refs/heads/cev-freq-adj.v10.fortglx-4.12-time

[2] fortglx/4.12/time

arch/x86/kernel/apic/apic.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 8ccb7ef512e0..875091d4609d 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -731,8 +731,10 @@ static int __init calibrate_APIC_clock(void)
TICK_NSEC, lapic_clockevent.shift);
lapic_clockevent.max_delta_ns =
clockevent_delta2ns(0x7FFFFF, &lapic_clockevent);
+ lapic_clockevent.max_delta_ticks = 0x7FFFFF;
lapic_clockevent.min_delta_ns =
clockevent_delta2ns(0xF, &lapic_clockevent);
+ lapic_clockevent.min_delta_ticks = 0xF;
lapic_clockevent.features &= ~CLOCK_EVT_FEAT_DUMMY;
return 0;
@@ -778,8 +780,10 @@ static int __init calibrate_APIC_clock(void)
lapic_clockevent.max_delta_ns =
clockevent_delta2ns(0x7FFFFFFF, &lapic_clockevent);
+ lapic_clockevent.max_delta_ticks = 0x7FFFFFFF;
lapic_clockevent.min_delta_ns =
clockevent_delta2ns(0xF, &lapic_clockevent);
+ lapic_clockevent.min_delta_ticks = 0xF;

lapic_timer_frequency = (delta * APIC_DIVISOR) / LAPIC_CAL_LOOPS;

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