xref: /netbsd-src/sys/sys/timetc.h (revision 9524b67c8d1f59f0cd1891af7cee826c04cff04a)
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@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