timetc.h

/*-
 * ----------------------------------------------------------------------------
 * "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
 * ----------------------------------------------------------------------------
 *
 * $FreeBSD: head/sys/sys/timetc.h 304285 2016-08-17 09:52:09Z kib $
 */

#ifndef _SYS_TIMETC_H_
#define _SYS_TIMETC_H_

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

/*-
 * `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;
#ifndef __rtems__
typedef u_int timecounter_get_t(struct timecounter *);
#else /* __rtems__ */
typedef uint32_t timecounter_get_t(struct timecounter *);
#endif /* __rtems__ */
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 (like sys/pci/xrpu.c) do.
         */
    uint32_t        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. */
#ifndef __rtems__
    timecounter_fill_vdso_timehands_t *tc_fill_vdso_timehands;
    timecounter_fill_vdso_timehands32_t *tc_fill_vdso_timehands32;
#endif /* __rtems__ */
};

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(int cnt);
void    cpu_tick_calibration(void);

#ifdef SYSCTL_DECL
SYSCTL_DECL(_kern_timecounter);
#endif

#endif /* !_SYS_TIMETC_H_ */