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e78f70bad2
In both the read callback for struct cyclecounter, and in struct timecounter, struct cyclecounter is declared as a const pointer. Unfortunatly, a number of users of this pointer treat it as a non-const pointer as it is burried in a larger structure that is heavily modified by the callback function when accessed. This lie had been hidden by the fact that container_of() "casts away" a const attribute of a pointer without any compiler warning happening at all. Fix this all up by removing the const attribute in the needed places so that everyone can see that the structure really isn't const, but can, and is, modified by the users of it. Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/all/2025070124-backyard-hurt-783a@gregkh
100 lines
2.5 KiB
C
100 lines
2.5 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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#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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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(const 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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