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
44 static inline void generic_sched_clock_init(void) { }
45
46 static inline void sched_clock_register(u64 (*read)(void), int bits,
47 unsigned long rate)
48 {
49 }
50 #endif
51
52 #endif
53
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