Commit-ID: 93825f2ec736f30e034ab7c9d56b42849c5b00da Gitweb: http://git.kernel.org/tip/93825f2ec736f30e034ab7c9d56b42849c5b00da Author: Frederic Weisbecker <fweis...@gmail.com> AuthorDate: Tue, 31 Jan 2017 04:09:16 +0100 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Wed, 1 Feb 2017 09:13:45 +0100
jiffies: Reuse TICK_NSEC instead of NSEC_PER_JIFFY NSEC_PER_JIFFY is an ad-hoc redefinition of TICK_NSEC. Let's rather use a unique and well maintained version. Signed-off-by: Frederic Weisbecker <fweis...@gmail.com> Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org> Cc: Paul Mackerras <pau...@samba.org> Cc: Michael Ellerman <m...@ellerman.id.au> Cc: Heiko Carstens <heiko.carst...@de.ibm.com> Cc: Martin Schwidefsky <schwidef...@de.ibm.com> Cc: Tony Luck <tony.l...@intel.com> Cc: Fenghua Yu <fenghua...@intel.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Rik van Riel <r...@redhat.com> Cc: Stanislaw Gruszka <sgrus...@redhat.com> Cc: Wanpeng Li <wanpeng...@hotmail.com> Link: http://lkml.kernel.org/r/1485832191-26889-1-git-send-email-fweis...@gmail.com Signed-off-by: Ingo Molnar <mi...@kernel.org> --- kernel/time/jiffies.c | 32 ++++++++++++++++---------------- 1 file changed, 16 insertions(+), 16 deletions(-) diff --git a/kernel/time/jiffies.c b/kernel/time/jiffies.c index a4a0e47..7906b3f 100644 --- a/kernel/time/jiffies.c +++ b/kernel/time/jiffies.c @@ -27,19 +27,8 @@ #include "timekeeping.h" -/* The Jiffies based clocksource is the lowest common - * denominator clock source which should function on - * all systems. It has the same coarse resolution as - * the timer interrupt frequency HZ and it suffers - * inaccuracies caused by missed or lost timer - * interrupts and the inability for the timer - * interrupt hardware to accuratly tick at the - * requested HZ value. It is also not recommended - * for "tick-less" systems. - */ -#define NSEC_PER_JIFFY ((NSEC_PER_SEC+HZ/2)/HZ) -/* Since jiffies uses a simple NSEC_PER_JIFFY multiplier +/* Since jiffies uses a simple TICK_NSEC multiplier * conversion, the .shift value could be zero. However * this would make NTP adjustments impossible as they are * in units of 1/2^.shift. Thus we use JIFFIES_SHIFT to @@ -47,8 +36,8 @@ * amount, and give ntp adjustments in units of 1/2^8 * * The value 8 is somewhat carefully chosen, as anything - * larger can result in overflows. NSEC_PER_JIFFY grows as - * HZ shrinks, so values greater than 8 overflow 32bits when + * larger can result in overflows. TICK_NSEC grows as HZ + * shrinks, so values greater than 8 overflow 32bits when * HZ=100. */ #if HZ < 34 @@ -64,12 +53,23 @@ static u64 jiffies_read(struct clocksource *cs) return (u64) jiffies; } +/* + * The Jiffies based clocksource is the lowest common + * denominator clock source which should function on + * all systems. It has the same coarse resolution as + * the timer interrupt frequency HZ and it suffers + * inaccuracies caused by missed or lost timer + * interrupts and the inability for the timer + * interrupt hardware to accuratly tick at the + * requested HZ value. It is also not recommended + * for "tick-less" systems. + */ static struct clocksource clocksource_jiffies = { .name = "jiffies", .rating = 1, /* lowest valid rating*/ .read = jiffies_read, .mask = CLOCKSOURCE_MASK(32), - .mult = NSEC_PER_JIFFY << JIFFIES_SHIFT, /* details above */ + .mult = TICK_NSEC << JIFFIES_SHIFT, /* details above */ .shift = JIFFIES_SHIFT, .max_cycles = 10, }; @@ -125,7 +125,7 @@ int register_refined_jiffies(long cycles_per_second) shift_hz += cycles_per_tick/2; do_div(shift_hz, cycles_per_tick); /* Calculate nsec_per_tick using shift_hz */ - nsec_per_tick = (u64)NSEC_PER_SEC << 8; + nsec_per_tick = (u64)TICK_NSEC << 8; nsec_per_tick += (u32)shift_hz/2; do_div(nsec_per_tick, (u32)shift_hz);
