Home Home > GIT Browse
diff options
authorChristopher S. Hall <christopher.s.hall@intel.com>2016-02-22 03:15:19 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-10-16 17:36:14 +0200
commit9b57d91c03054030f30be75c6e19c65b5f108ef3 (patch)
parent11bfbae19413a2ffe70378b6e572be263869a2bc (diff)
time: Add cycles to nanoseconds translation
commit 6bd58f09e1d8cc6c50a824c00bf0d617919986a1 upstream. The timekeeping code does not currently provide a way to translate externally provided clocksource cycles to system time. The cycle count is always provided by the result clocksource read() method internal to the timekeeping code. The added function timekeeping_cycles_to_ns() calculated a nanosecond value from a cycle count that can be added to tk_read_base.base value yielding the current system time. This allows clocksource cycle values external to the timekeeping code to provide a cycle count that can be transformed to system time. Cc: Prarit Bhargava <prarit@redhat.com> Cc: Richard Cochran <richardcochran@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: kevin.b.stanton@intel.com Cc: kevin.j.clarke@intel.com Cc: hpa@zytor.com Cc: jeffrey.t.kirsher@intel.com Cc: netdev@vger.kernel.org Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Christopher S. Hall <christopher.s.hall@intel.com> Signed-off-by: John Stultz <john.stultz@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 21 insertions, 4 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 4ff237dbc006..34c5b6351cd5 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -298,17 +298,34 @@ u32 (*arch_gettimeoffset)(void) = default_arch_gettimeoffset;
static inline u32 arch_gettimeoffset(void) { return 0; }
+static inline s64 timekeeping_delta_to_ns(struct tk_read_base *tkr,
+ cycle_t delta)
+ s64 nsec;
+ nsec = delta * tkr->mult + tkr->xtime_nsec;
+ nsec >>= tkr->shift;
+ /* If arch requires, add in get_arch_timeoffset() */
+ return nsec + arch_gettimeoffset();
static inline s64 timekeeping_get_ns(struct tk_read_base *tkr)
cycle_t delta;
- s64 nsec;
delta = timekeeping_get_delta(tkr);
+ return timekeeping_delta_to_ns(tkr, delta);
- nsec = (delta * tkr->mult + tkr->xtime_nsec) >> tkr->shift;
+static inline s64 timekeeping_cycles_to_ns(struct tk_read_base *tkr,
+ cycle_t cycles)
+ cycle_t delta;
- /* If arch requires, add in get_arch_timeoffset() */
- return nsec + arch_gettimeoffset();
+ /* calculate the delta since the last update_wall_time */
+ delta = clocksource_delta(cycles, tkr->cycle_last, tkr->mask);
+ return timekeeping_delta_to_ns(tkr, delta);