Commit-ID: 06c546110b0dafbc96c6eaf00aaa5835a18408c1 Gitweb: http://git.kernel.org/tip/06c546110b0dafbc96c6eaf00aaa5835a18408c1 Author: Nicolai Stange <nicstange@xxxxxxxxx> AuthorDate: Thu, 30 Mar 2017 21:54:55 +0200 Committer: John Stultz <john.stultz@xxxxxxxxxx> CommitDate: Fri, 14 Apr 2017 13:11:20 -0700 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 <mingo@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> Cc: Richard Cochran <richardcochran@xxxxxxxxx> Cc: Prarit Bhargava <prarit@xxxxxxxxxx> Cc: Stephen Boyd <sboyd@xxxxxxxxxxxxxx> Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx> Cc: David Hildenbrand <dahi@xxxxxxxxxxxxxxxxxx> Cc: linux-s390@xxxxxxxxxxxxxxx Signed-off-by: Nicolai Stange <nicstange@xxxxxxxxx> Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx> --- 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 c31da46..c3a52f9 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; -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
|