From 32f753f27032849de685c15c471034cbc945a544 Mon Sep 17 00:00:00 2001 From: "Bjoern A. Zeeb" Date: Mon, 24 May 2021 17:42:25 +0000 Subject: [PATCH] LinuxKPI: add Exponentially Weighted Moving Average implementation Add DECLARE_EWMA() which expands to a per-name EWMA implementation as used by multiple wireless drivers. Sposnored by: The FreeBSD Foundation MFC after: 2 weeks Reviewed by: hselasky, cperciva, dwmalone Differential Revision: https://reviews.freebsd.org/D30415 --- .../linuxkpi/common/include/linux/average.h | 92 +++++++++++++++++++ 1 file changed, 92 insertions(+) create mode 100644 sys/compat/linuxkpi/common/include/linux/average.h diff --git a/sys/compat/linuxkpi/common/include/linux/average.h b/sys/compat/linuxkpi/common/include/linux/average.h new file mode 100644 index 000000000000..4291bf2d85be --- /dev/null +++ b/sys/compat/linuxkpi/common/include/linux/average.h @@ -0,0 +1,92 @@ +/*- + * SPDX-License-Identifier: BSD-2-Clause + * + * Copyright (c) 2020-2021 The FreeBSD Foundation + * + * This software was developed by Björn Zeeb under sponsorship from + * the FreeBSD Foundation. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * + * $FreeBSD$ + */ + +#ifndef __LKPI_LINUX_AVERAGE_H +#define __LKPI_LINUX_AVERAGE_H + +#include +#include +#include +#include + +/* EWMA stands for Exponentially Weighted Moving Average. */ +/* + * Z_t = d X_t + (1 - d) * Z_(t-1); 0 < d <= 1, t >= 1; Roberts (1959). + * t : observation number in time. + * d : weight for current observation. + * Xt : observations over time. + * Zt : EWMA value after observation t. + * + * wmba_*_read seems to return up-to [u]long values; have to deal with 32/64bit. + * According to the ath5k.h change log this seems to be a fix-(_p)recision impl. + * assert 2/4 bits for frac. + * Also all (_d) values seem to be pow2 which simplifies maths (shift by + * d = ilog2(_d) instead of doing division (d = 1/_d)). Keep it this way until + * we hit the CTASSERT. + */ + +#define DECLARE_EWMA(_name, _p, _d) \ + \ + CTASSERT((sizeof(unsigned long) <= 4) ? (_p < 30) : (_p < 60)); \ + CTASSERT(_d > 0 && powerof2(_d)); \ + \ + struct ewma_ ## _name { \ + unsigned long zt; \ + }; \ + \ + static __inline void \ + ewma_ ## _name ## _init(struct ewma_ ## _name *ewma) \ + { \ + /* No target (no historical data). */ \ + ewma->zt = 0; \ + } \ + \ + static __inline void \ + ewma_ ## _name ## _add(struct ewma_ ## _name *ewma, unsigned long x) \ + { \ + unsigned long ztm1 = ewma->zt; /* Z_(t-1). */ \ + int d = ilog2(_d); \ + \ + if (ewma->zt == 0) \ + ewma->zt = x << (_p); \ + else \ + ewma->zt = ((x << (_p)) >> d) + \ + (((ztm1 << d) - ztm1) >> d); \ + } \ + \ + static __inline unsigned long \ + ewma_ ## _name ## _read(struct ewma_ ## _name *ewma) \ + { \ + return (ewma->zt >> (_p)); \ + } \ + +#endif /* __LKPI_LINUX_AVERAGE_H */