]>
Commit | Line | Data |
---|---|---|
b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
c5485a7e BR |
2 | #ifndef _LINUX_AVERAGE_H |
3 | #define _LINUX_AVERAGE_H | |
4 | ||
eb1e011a JB |
5 | /* |
6 | * Exponentially weighted moving average (EWMA) | |
7 | * | |
8 | * This implements a fixed-precision EWMA algorithm, with both the | |
9 | * precision and fall-off coefficient determined at compile-time | |
10 | * and built into the generated helper funtions. | |
11 | * | |
12 | * The first argument to the macro is the name that will be used | |
13 | * for the struct and helper functions. | |
14 | * | |
15 | * The second argument, the precision, expresses how many bits are | |
16 | * used for the fractional part of the fixed-precision values. | |
17 | * | |
18 | * The third argument, the weight reciprocal, determines how the | |
19 | * new values will be weighed vs. the old state, new values will | |
20 | * get weight 1/weight_rcp and old values 1-1/weight_rcp. Note | |
21 | * that this parameter must be a power of two for efficiency. | |
22 | */ | |
c5485a7e | 23 | |
eb1e011a | 24 | #define DECLARE_EWMA(name, _precision, _weight_rcp) \ |
2377799c JB |
25 | struct ewma_##name { \ |
26 | unsigned long internal; \ | |
27 | }; \ | |
28 | static inline void ewma_##name##_init(struct ewma_##name *e) \ | |
29 | { \ | |
eb1e011a JB |
30 | BUILD_BUG_ON(!__builtin_constant_p(_precision)); \ |
31 | BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp)); \ | |
32 | /* \ | |
33 | * Even if you want to feed it just 0/1 you should have \ | |
34 | * some bits for the non-fractional part... \ | |
35 | */ \ | |
36 | BUILD_BUG_ON((_precision) > 30); \ | |
37 | BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp); \ | |
2377799c JB |
38 | e->internal = 0; \ |
39 | } \ | |
40 | static inline unsigned long \ | |
41 | ewma_##name##_read(struct ewma_##name *e) \ | |
42 | { \ | |
eb1e011a JB |
43 | BUILD_BUG_ON(!__builtin_constant_p(_precision)); \ |
44 | BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp)); \ | |
45 | BUILD_BUG_ON((_precision) > 30); \ | |
46 | BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp); \ | |
47 | return e->internal >> (_precision); \ | |
2377799c JB |
48 | } \ |
49 | static inline void ewma_##name##_add(struct ewma_##name *e, \ | |
50 | unsigned long val) \ | |
51 | { \ | |
52 | unsigned long internal = ACCESS_ONCE(e->internal); \ | |
eb1e011a JB |
53 | unsigned long weight_rcp = ilog2(_weight_rcp); \ |
54 | unsigned long precision = _precision; \ | |
2377799c | 55 | \ |
eb1e011a JB |
56 | BUILD_BUG_ON(!__builtin_constant_p(_precision)); \ |
57 | BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp)); \ | |
58 | BUILD_BUG_ON((_precision) > 30); \ | |
59 | BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp); \ | |
2377799c JB |
60 | \ |
61 | ACCESS_ONCE(e->internal) = internal ? \ | |
eb1e011a JB |
62 | (((internal << weight_rcp) - internal) + \ |
63 | (val << precision)) >> weight_rcp : \ | |
64 | (val << precision); \ | |
2377799c JB |
65 | } |
66 | ||
c5485a7e | 67 | #endif /* _LINUX_AVERAGE_H */ |