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Date: Fri, 31 Mar 2017 14:03:22 +1100 From: Michael Ellerman <mpe@...erman.id.au> To: Nicolai Stange <nicstange@...il.com>, Benjamin Herrenschmidt <benh@...nel.crashing.org>, Paul Mackerras <paulus@...ba.org> Cc: John Stultz <john.stultz@...aro.org>, linux-kernel@...r.kernel.org, Nicolai Stange <nicstange@...il.com>, Ingo Molnar <mingo@...nel.org>, Frédéric Weisbecker <fweisbec@...il.com>, Thomas Gleixner <tglx@...utronix.de>, Oliver O'Halloran <oohall@...il.com>, linuxppc-dev@...ts.ozlabs.org Subject: Re: [PATCH] powerpc/time: set ->min_delta_ticks and ->max_delta_ticks Nicolai Stange <nicstange@...il.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 powerpc arch's 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@...il.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/powerpc/kernel/time.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c > index 07b90725855e..2b33cfaac7b8 100644 > --- a/arch/powerpc/kernel/time.c > +++ b/arch/powerpc/kernel/time.c > @@ -995,8 +995,10 @@ static void __init init_decrementer_clockevent(void) > > decrementer_clockevent.max_delta_ns = > clockevent_delta2ns(decrementer_max, &decrementer_clockevent); > + decrementer_clockevent.max_delta_ticks = decrementer_max; > decrementer_clockevent.min_delta_ns = > clockevent_delta2ns(2, &decrementer_clockevent); > + decrementer_clockevent.min_delta_ticks = 2; Seems to do what it says on the tin. Acked-by: Michael Ellerman <mpe@...erman.id.au> (powerpc) cheers
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