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Diffstat (limited to 'include/linux/timecompare.h')
| -rw-r--r-- | include/linux/timecompare.h | 125 |
1 files changed, 0 insertions, 125 deletions
diff --git a/include/linux/timecompare.h b/include/linux/timecompare.h deleted file mode 100644 index 546e2234e4b..00000000000 --- a/include/linux/timecompare.h +++ /dev/null @@ -1,125 +0,0 @@ -/* - * Utility code which helps transforming between two different time - * bases, called "source" and "target" time in this code. - * - * Source time has to be provided via the timecounter API while target - * time is accessed via a function callback whose prototype - * intentionally matches ktime_get() and ktime_get_real(). These - * interfaces where chosen like this so that the code serves its - * initial purpose without additional glue code. - * - * This purpose is synchronizing a hardware clock in a NIC with system - * time, in order to implement the Precision Time Protocol (PTP, - * IEEE1588) with more accurate hardware assisted time stamping. In - * that context only synchronization against system time (= - * ktime_get_real()) is currently needed. But this utility code might - * become useful in other situations, which is why it was written as - * general purpose utility code. - * - * The source timecounter is assumed to return monotonically - * increasing time (but this code does its best to compensate if that - * is not the case) whereas target time may jump. - * - * The target time corresponding to a source time is determined by - * reading target time, reading source time, reading target time - * again, then assuming that average target time corresponds to source - * time. In other words, the assumption is that reading the source - * time is slow and involves equal time for sending the request and - * receiving the reply, whereas reading target time is assumed to be - * fast. - * - * Copyright (C) 2009 Intel Corporation. - * Author: Patrick Ohly <patrick.ohly@intel.com> - * - * This program is free software; you can redistribute it and/or modify it - * under the terms and conditions of the GNU General Public License, - * version 2, as published by the Free Software Foundation. - * - * This program is distributed in the hope it will be useful, but WITHOUT - * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or - * FITNESS FOR A PARTICULAR PURPOSE. * See the GNU General Public License for - * more details. - * - * You should have received a copy of the GNU General Public License along with - * this program; if not, write to the Free Software Foundation, Inc., - * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA. - */ -#ifndef _LINUX_TIMECOMPARE_H -#define _LINUX_TIMECOMPARE_H - -#include <linux/clocksource.h> -#include <linux/ktime.h> - -/** - * struct timecompare - stores state and configuration for the two clocks - * - * Initialize to zero, then set source/target/num_samples. - * - * Transformation between source time and target time is done with: - * target_time = source_time + offset + - * (source_time - last_update) * skew / - * TIMECOMPARE_SKEW_RESOLUTION - * - * @source: used to get source time stamps via timecounter_read() - * @target: function returning target time (for example, ktime_get - * for monotonic time, or ktime_get_real for wall clock) - * @num_samples: number of times that source time and target time are to - * be compared when determining their offset - * @offset: (target time - source time) at the time of the last update - * @skew: average (target time - source time) / delta source time * - * TIMECOMPARE_SKEW_RESOLUTION - * @last_update: last source time stamp when time offset was measured - */ -struct timecompare { - struct timecounter *source; - ktime_t (*target)(void); - int num_samples; - - s64 offset; - s64 skew; - u64 last_update; -}; - -/** - * timecompare_transform - transform source time stamp into target time base - * @sync: context for time sync - * @source_tstamp: the result of timecounter_read() or - * timecounter_cyc2time() - */ -extern ktime_t timecompare_transform(struct timecompare *sync, - u64 source_tstamp); - -/** - * timecompare_offset - measure current (target time - source time) offset - * @sync: context for time sync - * @offset: average offset during sample period returned here - * @source_tstamp: average source time during sample period returned here - * - * Returns number of samples used. Might be zero (= no result) in the - * unlikely case that target time was monotonically decreasing for all - * samples (= broken). - */ -extern int timecompare_offset(struct timecompare *sync, - s64 *offset, - u64 *source_tstamp); - -extern void __timecompare_update(struct timecompare *sync, - u64 source_tstamp); - -/** - * timecompare_update - update offset and skew by measuring current offset - * @sync: context for time sync - * @source_tstamp: the result of timecounter_read() or - * timecounter_cyc2time(), pass zero to force update - * - * Updates are only done at most once per second. - */ -static inline void timecompare_update(struct timecompare *sync, - u64 source_tstamp) -{ - if (!source_tstamp || - (s64)(source_tstamp - sync->last_update) >= NSEC_PER_SEC) - __timecompare_update(sync, source_tstamp); -} - -#endif /* _LINUX_TIMECOMPARE_H */ |