/*-
 * SPDX-License-Identifier: Beerware
 *
 * ----------------------------------------------------------------------------
 * "THE BEER-WARE LICENSE" (Revision 42):
 * <phk@FreeBSD.ORG> wrote this file.  As long as you retain this notice you
 * can do whatever you want with this stuff. If we meet some day, and you think
 * this stuff is worth it, you can buy me a beer in return.   Poul-Henning Kamp
 * ----------------------------------------------------------------------------
 */

#ifndef _SYS_TIMETC_H_
#define _SYS_TIMETC_H_

#ifndef _KERNEL
#error "no user-serviceable parts inside"
#endif

/*-
 * `struct timecounter' is the interface between the hardware which implements
 * a timecounter and the MI code which uses this to keep track of time.
 *
 * A timecounter is a binary counter which has two properties:
 *    * it runs at a fixed, known frequency.
 *    * it has sufficient bits to not roll over in less than approximately
 *      max(2 msec, 2/HZ seconds).  (The value 2 here is really 1 + delta,
 *      for some indeterminate value of delta.)
 */

struct timecounter;
struct vdso_timehands;
struct vdso_timehands32;
typedef u_int timecounter_get_t(struct timecounter *);
typedef void timecounter_pps_t(struct timecounter *);
typedef uint32_t timecounter_fill_vdso_timehands_t(struct vdso_timehands *,
    struct timecounter *);
typedef uint32_t timecounter_fill_vdso_timehands32_t(struct vdso_timehands32 *,
    struct timecounter *);

struct timecounter {
        timecounter_get_t       *tc_get_timecount;
                /*
                 * This function reads the counter.  It is not required to
                 * mask any unimplemented bits out, as long as they are
                 * constant.
                 */
        timecounter_pps_t       *tc_poll_pps;
                /*
                 * This function is optional.  It will be called whenever the
                 * timecounter is rewound, and is intended to check for PPS
                 * events.  Normal hardware does not need it but timecounters
                 * which latch PPS in hardware do.
                 */
        u_int                   tc_counter_mask;
                /* This mask should mask off any unimplemented bits. */
        uint64_t                tc_frequency;
                /* Frequency of the counter in Hz. */
        const char              *tc_name;
                /* Name of the timecounter. */
        int                     tc_quality;
                /*
                 * Used to determine if this timecounter is better than
                 * another timecounter higher means better.  Negative
                 * means "only use at explicit request".
                 */
        u_int                   tc_flags;
#define TC_FLAGS_C2STOP         1       /* Timer dies in C2+. */
#define TC_FLAGS_SUSPEND_SAFE   2       /*
                                         * Timer functional across
                                         * suspend/resume.
                                         */

        void                    *tc_priv;
                /* Pointer to the timecounter's private parts. */
        struct timecounter      *tc_next;
                /* Pointer to the next timecounter. */
        timecounter_fill_vdso_timehands_t *tc_fill_vdso_timehands;
        timecounter_fill_vdso_timehands32_t *tc_fill_vdso_timehands32;
};

extern struct timecounter *timecounter;
extern int tc_min_ticktock_freq; /*
                                  * Minimal tc_ticktock() call frequency,
                                  * required to handle counter wraps.
                                  */

u_int64_t tc_getfrequency(void);
void    tc_init(struct timecounter *tc);
void    tc_setclock(struct timespec *ts);
void    tc_ticktock(long cnt);
void    cpu_tick_calibration(void);

#ifdef SYSCTL_DECL
SYSCTL_DECL(_kern_timecounter);
#endif

/**
 * clockcalib(clk, clkname):
 * Return the frequency of the provided timer, as calibrated against the
 * current best-available timecounter.
 */
uint64_t clockcalib(uint64_t (*)(void), const char *);

#endif /* !_SYS_TIMETC_H_ */