| 1 | |
| 2 | |
| 3 | * Based on clocksource code. See commit 74d23cc704d1
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| 4 |
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| 5 | #include <linux/export.h>
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| 6 | #include <linux/timecounter.h>
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| 7 |
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| 8 | void timecounter_init(struct timecounter *tc,
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| 9 | struct cyclecounter *cc,
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| 10 | u64 start_tstamp)
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| 11 | {
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| 12 | tc->cc = cc;
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| 13 | tc->cycle_last = cc->read(cc);
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| 14 | tc->nsec = start_tstamp;
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| 15 | tc->mask = (1ULL << cc->shift) - 1;
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| 16 | tc->frac = 0;
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| 17 | }
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| 18 | EXPORT_SYMBOL_GPL(timecounter_init);
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| 19 |
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| 20 | |
| 21 | * timecounter_read_delta - get nanoseconds since last call of this function
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| 22 | * @tc: Pointer to time counter
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| 23 | *
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| 24 | * When the underlying cycle counter runs over, this will be handled
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| 25 | * correctly as long as it does not run over more than once between
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| 26 | * calls.
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| 27 | *
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| 28 | * The first call to this function for a new time counter initializes
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| 29 | * the time tracking and returns an undefined result.
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| 30 |
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| 31 | static u64 timecounter_read_delta(struct timecounter *tc)
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| 32 | {
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| 33 | u64 cycle_now, cycle_delta;
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| 34 | u64 ns_offset;
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| 35 |
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| 36 |
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| 37 | cycle_now = tc->cc->read(tc->cc);
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| 38 |
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| 39 |
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| 40 | cycle_delta = (cycle_now - tc->cycle_last) & tc->cc->mask;
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| 41 |
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| 42 |
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| 43 | ns_offset = cyclecounter_cyc2ns(tc->cc, cycle_delta,
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| 44 | tc->mask, &tc->frac);
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| 45 |
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| 46 |
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| 47 | tc->cycle_last = cycle_now;
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| 48 |
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| 49 | return ns_offset;
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| 50 | }
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| 51 |
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| 52 | u64 timecounter_read(struct timecounter *tc)
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| 53 | {
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| 54 | u64 nsec;
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| 55 |
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| 56 |
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| 57 | nsec = timecounter_read_delta(tc);
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| 58 | nsec += tc->nsec;
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| 59 | tc->nsec = nsec;
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| 60 |
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| 61 | return nsec;
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| 62 | }
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| 63 | EXPORT_SYMBOL_GPL(timecounter_read);
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| 64 |
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