From 06c546110b0dafbc96c6eaf00aaa5835a18408c1 Mon Sep 17 00:00:00 2001 From: Nicolai Stange Date: Thu, 30 Mar 2017 21:54:55 +0200 Subject: [PATCH] s390/time: 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. Currently, the s390's CPU timer clockevent device is initialized as follows: cd->min_delta_ns = 1; cd->max_delta_ns = LONG_MAX; Note that the device's time to cycle conversion factor, i.e. cd->mult / (2^cd->shift), is approx. equal to 4. Hence, this would translate to cd->min_delta_ticks = 4; cd->max_delta_ticks = 4 * LONG_MAX; However, a minimum value of 1ns is in the range of noise anyway and the clockevent core will take care of this by increasing it to 1us or so. Furthermore, 4*LONG_MAX would overflow the unsigned long argument the clockevent devices gets programmed with. Thus, initialize ->min_delta_ticks with 1 and ->max_delta_ticks with ULONG_MAX. 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. Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Daniel Lezcano Cc: Richard Cochran Cc: Prarit Bhargava Cc: Stephen Boyd Cc: Martin Schwidefsky Cc: Heiko Carstens Cc: David Hildenbrand Cc: linux-s390@vger.kernel.org Signed-off-by: Nicolai Stange Signed-off-by: John Stultz --- arch/s390/kernel/time.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c index c31da46bc037..c3a52f9a69a0 100644 --- a/arch/s390/kernel/time.c +++ b/arch/s390/kernel/time.c @@ -158,7 +158,9 @@ void init_cpu_timer(void) cd->mult = 16777; cd->shift = 12; cd->min_delta_ns = 1; + cd->min_delta_ticks = 1; cd->max_delta_ns = LONG_MAX; + cd->max_delta_ticks = ULONG_MAX; cd->rating = 400; cd->cpumask = cpumask_of(cpu); cd->set_next_event = s390_next_event; -- 2.39.5