| /* SPDX-License-Identifier: GPL-2.0-or-later */ |
| /* |
| * linux/include/linux/timecounter.h |
| * |
| * based on code that migrated away from |
| * linux/include/linux/clocksource.h |
| */ |
| #ifndef _LINUX_TIMECOUNTER_H |
| #define _LINUX_TIMECOUNTER_H |
| |
| #include <linux/types.h> |
| |
| /* simplify initialization of mask field */ |
| #define CYCLECOUNTER_MASK(bits) (u64)((bits) < 64 ? ((1ULL<<(bits))-1) : -1) |
| |
| /** |
| * struct cyclecounter - hardware abstraction for a free running counter |
| * Provides completely state-free accessors to the underlying hardware. |
| * Depending on which hardware it reads, the cycle counter may wrap |
| * around quickly. Locking rules (if necessary) have to be defined |
| * by the implementor and user of specific instances of this API. |
| * |
| * @read: returns the current cycle value |
| * @mask: bitmask for two's complement |
| * subtraction of non 64 bit counters, |
| * see CYCLECOUNTER_MASK() helper macro |
| * @mult: cycle to nanosecond multiplier |
| * @shift: cycle to nanosecond divisor (power of two) |
| */ |
| struct cyclecounter { |
| u64 (*read)(const struct cyclecounter *cc); |
| u64 mask; |
| u32 mult; |
| u32 shift; |
| }; |
| |
| /** |
| * struct timecounter - layer above a %struct cyclecounter which counts nanoseconds |
| * Contains the state needed by timecounter_read() to detect |
| * cycle counter wrap around. Initialize with |
| * timecounter_init(). Also used to convert cycle counts into the |
| * corresponding nanosecond counts with timecounter_cyc2time(). Users |
| * of this code are responsible for initializing the underlying |
| * cycle counter hardware, locking issues and reading the time |
| * more often than the cycle counter wraps around. The nanosecond |
| * counter will only wrap around after ~585 years. |
| * |
| * @cc: the cycle counter used by this instance |
| * @cycle_last: most recent cycle counter value seen by |
| * timecounter_read() |
| * @nsec: continuously increasing count |
| * @mask: bit mask for maintaining the 'frac' field |
| * @frac: accumulated fractional nanoseconds |
| */ |
| struct timecounter { |
| const struct cyclecounter *cc; |
| u64 cycle_last; |
| u64 nsec; |
| u64 mask; |
| u64 frac; |
| }; |
| |
| /** |
| * cyclecounter_cyc2ns - converts cycle counter cycles to nanoseconds |
| * @cc: Pointer to cycle counter. |
| * @cycles: Cycles |
| * @mask: bit mask for maintaining the 'frac' field |
| * @frac: pointer to storage for the fractional nanoseconds. |
| */ |
| static inline u64 cyclecounter_cyc2ns(const struct cyclecounter *cc, |
| u64 cycles, u64 mask, u64 *frac) |
| { |
| u64 ns = (u64) cycles; |
| |
| ns = (ns * cc->mult) + *frac; |
| *frac = ns & mask; |
| return ns >> cc->shift; |
| } |
| |
| /** |
| * timecounter_adjtime - Shifts the time of the clock. |
| * @delta: Desired change in nanoseconds. |
| */ |
| static inline void timecounter_adjtime(struct timecounter *tc, s64 delta) |
| { |
| tc->nsec += delta; |
| } |
| |
| /** |
| * timecounter_init - initialize a time counter |
| * @tc: Pointer to time counter which is to be initialized/reset |
| * @cc: A cycle counter, ready to be used. |
| * @start_tstamp: Arbitrary initial time stamp. |
| * |
| * After this call the current cycle register (roughly) corresponds to |
| * the initial time stamp. Every call to timecounter_read() increments |
| * the time stamp counter by the number of elapsed nanoseconds. |
| */ |
| extern void timecounter_init(struct timecounter *tc, |
| const struct cyclecounter *cc, |
| u64 start_tstamp); |
| |
| /** |
| * timecounter_read - return nanoseconds elapsed since timecounter_init() |
| * plus the initial time stamp |
| * @tc: Pointer to time counter. |
| * |
| * In other words, keeps track of time since the same epoch as |
| * the function which generated the initial time stamp. |
| */ |
| extern u64 timecounter_read(struct timecounter *tc); |
| |
| /** |
| * timecounter_cyc2time - convert a cycle counter to same |
| * time base as values returned by |
| * timecounter_read() |
| * @tc: Pointer to time counter. |
| * @cycle_tstamp: a value returned by tc->cc->read() |
| * |
| * Cycle counts that are converted correctly as long as they |
| * fall into the interval [-1/2 max cycle count, +1/2 max cycle count], |
| * with "max cycle count" == cs->mask+1. |
| * |
| * This allows conversion of cycle counter values which were generated |
| * in the past. |
| */ |
| extern u64 timecounter_cyc2time(struct timecounter *tc, |
| u64 cycle_tstamp); |
| |
| #endif |