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      1 /* $NetBSD: timetc.h,v 1.9 2020/09/04 00:36:07 thorpej Exp $ */
      2 
      3 /*-
      4  * ----------------------------------------------------------------------------
      5  * "THE BEER-WARE LICENSE" (Revision 42):
      6  * <phk (at) FreeBSD.ORG> wrote this file.  As long as you retain this notice you
      7  * can do whatever you want with this stuff. If we meet some day, and you think
      8  * this stuff is worth it, you can buy me a beer in return.   Poul-Henning Kamp
      9  * ----------------------------------------------------------------------------
     10  *
     11  * $FreeBSD: src/sys/sys/timetc.h,v 1.58 2003/08/16 08:23:52 phk Exp $
     12  */
     13 
     14 #ifndef _SYS_TIMETC_H_
     15 #define	_SYS_TIMETC_H_
     16 
     17 #if !defined(_KERNEL) && !defined(_KMEMUSER)
     18 #error "no user-serviceable parts inside"
     19 #endif
     20 
     21 /*
     22  * max recommended timecounter name length
     23  *
     24  * it is not a functional limit but names longer
     25  * then that will not be controllable via
     26  * sysctl. see kern/kern_tc.c for the sysctl
     27  * implementation.
     28  */
     29 #define MAX_TCNAMELEN	64
     30 
     31 /*-
     32  * `struct timecounter' is the interface between the hardware which implements
     33  * a timecounter and the MI code which uses this to keep track of time.
     34  *
     35  * A timecounter is a binary counter which has two properties:
     36  *    * it runs at a fixed, known frequency.
     37  *    * it has sufficient bits to not roll over in less than approximately
     38  *      max(2 msec, 2/HZ seconds).  (The value 2 here is really 1 + delta,
     39  *      for some indeterminate value of delta.)
     40  */
     41 
     42 struct timecounter;
     43 struct timespec;
     44 typedef u_int timecounter_get_t(struct timecounter *);
     45 typedef void timecounter_pps_t(struct timecounter *);
     46 
     47 struct timecounter {
     48 	timecounter_get_t	*tc_get_timecount;
     49 		/*
     50 		 * This function reads the counter.  It is not required to
     51 		 * mask any unimplemented bits out, as long as they are
     52 		 * constant.
     53 		 */
     54 	timecounter_pps_t	*tc_poll_pps;
     55 		/*
     56 		 * This function is optional.  It will be called whenever the
     57 		 * timecounter is rewound, and is intended to check for PPS
     58 		 * events.  Normal hardware does not need it but timecounters
     59 		 * which latch PPS in hardware (like sys/pci/xrpu.c) do.
     60 		 */
     61 	u_int 			tc_counter_mask;
     62 		/* This mask should mask off any unimplemented bits. */
     63 	uint64_t		tc_frequency;
     64 		/* Frequency of the counter in Hz. */
     65 	const char		*tc_name;
     66 		/* Name of the timecounter. */
     67 	int			tc_quality;
     68 		/*
     69 		 * Used to determine if this timecounter is better than
     70 		 * another timecounter higher means better.  Negative
     71 		 * means "only use at explicit request".
     72 		 */
     73 
     74 	void			*tc_priv;
     75 		/* Pointer to the timecounter's private parts. */
     76 	struct timecounter	*tc_next;
     77 		/* Pointer to the next timecounter. */
     78 };
     79 
     80 #ifdef _KERNEL
     81 extern struct timecounter *timecounter;
     82 
     83 uint64_t tc_getfrequency(void);
     84 void	tc_init(struct timecounter *tc);
     85 int	tc_detach(struct timecounter *);
     86 void	tc_setclock(const struct timespec *ts);
     87 void	tc_ticktock(void);
     88 void	tc_gonebad(struct timecounter *);
     89 
     90 #ifdef SYSCTL_DECL
     91 SYSCTL_DECL(_kern_timecounter);
     92 #endif
     93 #endif /* _KERNEL */
     94 
     95 #endif /* !_SYS_TIMETC_H_ */
     96