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35728b8209
Update the time(r) core files files with the correct SPDX license identifier based on the license text in the file itself. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This work is based on a script and data from Philippe Ombredanne, Kate Stewart and myself. The data has been created with two independent license scanners and manual inspection. The following files do not contain any direct license information and have been omitted from the big initial SPDX changes: timeconst.bc: The .bc files were not touched time.c, timer.c, timekeeping.c: Licence was deduced from EXPORT_SYMBOL_GPL As those files do not contain direct license references they fall under the project license, i.e. GPL V2 only. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Kees Cook <keescook@chromium.org> Acked-by: Ingo Molnar <mingo@kernel.org> Acked-by: John Stultz <john.stultz@linaro.org> Acked-by: Corey Minyard <cminyard@mvista.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Kate Stewart <kstewart@linuxfoundation.org> Cc: Philippe Ombredanne <pombredanne@nexb.com> Cc: Russell King <rmk+kernel@armlinux.org.uk> Cc: Richard Cochran <richardcochran@gmail.com> Cc: Nicolas Pitre <nicolas.pitre@linaro.org> Cc: David Riley <davidriley@chromium.org> Cc: Colin Cross <ccross@android.com> Cc: Mark Brown <broonie@kernel.org> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Link: https://lkml.kernel.org/r/20181031182252.879109557@linutronix.de
110 lines
3.0 KiB
C
110 lines
3.0 KiB
C
// SPDX-License-Identifier: GPL-2.0+
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/*
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* Based on clocksource code. See commit 74d23cc704d1
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#include <linux/export.h>
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#include <linux/timecounter.h>
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void timecounter_init(struct timecounter *tc,
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const struct cyclecounter *cc,
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u64 start_tstamp)
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{
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tc->cc = cc;
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tc->cycle_last = cc->read(cc);
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tc->nsec = start_tstamp;
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tc->mask = (1ULL << cc->shift) - 1;
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tc->frac = 0;
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}
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EXPORT_SYMBOL_GPL(timecounter_init);
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/**
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* timecounter_read_delta - get nanoseconds since last call of this function
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* @tc: Pointer to time counter
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*
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* When the underlying cycle counter runs over, this will be handled
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* correctly as long as it does not run over more than once between
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* calls.
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*
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* The first call to this function for a new time counter initializes
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* the time tracking and returns an undefined result.
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*/
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static u64 timecounter_read_delta(struct timecounter *tc)
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{
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u64 cycle_now, cycle_delta;
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u64 ns_offset;
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/* read cycle counter: */
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cycle_now = tc->cc->read(tc->cc);
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/* calculate the delta since the last timecounter_read_delta(): */
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cycle_delta = (cycle_now - tc->cycle_last) & tc->cc->mask;
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/* convert to nanoseconds: */
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ns_offset = cyclecounter_cyc2ns(tc->cc, cycle_delta,
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tc->mask, &tc->frac);
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/* update time stamp of timecounter_read_delta() call: */
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tc->cycle_last = cycle_now;
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return ns_offset;
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}
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u64 timecounter_read(struct timecounter *tc)
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{
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u64 nsec;
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/* increment time by nanoseconds since last call */
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nsec = timecounter_read_delta(tc);
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nsec += tc->nsec;
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tc->nsec = nsec;
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return nsec;
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}
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EXPORT_SYMBOL_GPL(timecounter_read);
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/*
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* This is like cyclecounter_cyc2ns(), but it is used for computing a
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* time previous to the time stored in the cycle counter.
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*/
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static u64 cc_cyc2ns_backwards(const struct cyclecounter *cc,
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u64 cycles, u64 mask, u64 frac)
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{
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u64 ns = (u64) cycles;
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ns = ((ns * cc->mult) - frac) >> cc->shift;
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return ns;
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}
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u64 timecounter_cyc2time(struct timecounter *tc,
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u64 cycle_tstamp)
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{
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u64 delta = (cycle_tstamp - tc->cycle_last) & tc->cc->mask;
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u64 nsec = tc->nsec, frac = tc->frac;
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/*
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* Instead of always treating cycle_tstamp as more recent
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* than tc->cycle_last, detect when it is too far in the
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* future and treat it as old time stamp instead.
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*/
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if (delta > tc->cc->mask / 2) {
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delta = (tc->cycle_last - cycle_tstamp) & tc->cc->mask;
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nsec -= cc_cyc2ns_backwards(tc->cc, delta, tc->mask, frac);
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} else {
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nsec += cyclecounter_cyc2ns(tc->cc, delta, tc->mask, &frac);
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}
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return nsec;
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}
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EXPORT_SYMBOL_GPL(timecounter_cyc2time);
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