xref: /netbsd-src/sys/external/bsd/drm2/include/linux/average.h (revision 15c215b6ab309a6063791984233e66c517ecf3a8)
1 /*	$NetBSD: average.h,v 1.2 2021/12/19 10:38:38 riastradh Exp $	*/
2 
3 /*-
4  * Copyright (c) 2020 The NetBSD Foundation, Inc.
5  * All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  *
16  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
26  * POSSIBILITY OF SUCH DAMAGE.
27  */
28 
29 #ifndef	_LINUX_AVERAGE_H_
30 #define	_LINUX_AVERAGE_H_
31 
32 #define	DECLARE_EWMA(NAME, PREC, RATE)					      \
33 struct ewma_##NAME {							      \
34 	unsigned long ewma_state;					      \
35 };									      \
36 									      \
37 static inline void							      \
38 ewma_##NAME##_init(struct ewma_##NAME *ewma)				      \
39 {									      \
40 	ewma->ewma_state = 0;						      \
41 }									      \
42 									      \
43 static inline unsigned long						      \
44 ewma_##NAME##_read(struct ewma_##NAME *ewma)				      \
45 {									      \
46 	return ewma->ewma_state >> (PREC);				      \
47 }									      \
48 									      \
49 static inline void							      \
50 ewma_##NAME##_add(struct ewma_##NAME *ewma, unsigned long sample)	      \
51 {									      \
52 	const unsigned long shift = ilog2(RATE);			      \
53 	const unsigned long state = ewma->ewma_state;			      \
54 									      \
55 	sample <<= (PREC);						      \
56 	if (state == 0) {						      \
57 		ewma->ewma_state = sample;				      \
58 		return;							      \
59 	}								      \
60 	ewma->ewma_state = (((state << shift) - state) + sample) >> shift;    \
61 }
62 
63 #endif	/* _LINUX_AVERAGE_H_ */
64