1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3  * sched_clock.h: support for extending counters to full 64-bit ns counter
4  */
5 #ifndef LINUX_SCHED_CLOCK
6 #define LINUX_SCHED_CLOCK
7 
8 #include <linux/types.h>
9 
10 #ifdef CONFIG_GENERIC_SCHED_CLOCK
11 /**
12  * struct clock_read_data - data required to read from sched_clock()
13  *
14  * @epoch_ns:		sched_clock() value at last update
15  * @epoch_cyc:		Clock cycle value at last update.
16  * @sched_clock_mask:   Bitmask for two's complement subtraction of non 64bit
17  *			clocks.
18  * @read_sched_clock:	Current clock source (or dummy source when suspended).
19  * @mult:		Multiplier for scaled math conversion.
20  * @shift:		Shift value for scaled math conversion.
21  *
22  * Care must be taken when updating this structure; it is read by
23  * some very hot code paths. It occupies <=40 bytes and, when combined
24  * with the seqcount used to synchronize access, comfortably fits into
25  * a 64 byte cache line.
26  */
27 struct clock_read_data {
28 	u64 epoch_ns;
29 	u64 epoch_cyc;
30 	u64 sched_clock_mask;
31 	u64 (*read_sched_clock)(void);
32 	u32 mult;
33 	u32 shift;
34 };
35 
36 extern struct clock_read_data *sched_clock_read_begin(unsigned int *seq);
37 extern int sched_clock_read_retry(unsigned int seq);
38 
39 extern void generic_sched_clock_init(void);
40 
41 extern void sched_clock_register(u64 (*read)(void), int bits,
42 				 unsigned long rate);
43 #else
generic_sched_clock_init(void)44 static inline void generic_sched_clock_init(void) { }
45 
sched_clock_register(u64 (* read)(void),int bits,unsigned long rate)46 static inline void sched_clock_register(u64 (*read)(void), int bits,
47 					unsigned long rate)
48 {
49 }
50 #endif
51 
52 #endif
53