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freebsd
GitHub Repository: freebsd/freebsd-src
 Path: blob/main/sys/dev/bwn/if_bwn_cordic.h
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/*-

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 * Copyright (c) 2016 Adrian Chadd <[email protected]>

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 * All rights reserved.

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 *

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 * Redistribution and use in source and binary forms, with or without

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 * modification, are permitted provided that the following conditions

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 * are met:

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 * 1. Redistributions of source code must retain the above copyright

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 *    notice, this list of conditions and the following disclaimer,

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 *    without modification.

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 * 2. Redistributions in binary form must reproduce at minimum a disclaimer

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 *    similar to the "NO WARRANTY" disclaimer below ("Disclaimer") and any

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 *    redistribution must be conditioned upon including a substantially

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 *    similar Disclaimer requirement for further binary redistribution.

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 *

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 * NO WARRANTY

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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

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 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

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 * LIMITED TO, THE IMPLIED WARRANTIES OF NONINFRINGEMENT, MERCHANTIBILITY

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 * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL

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 * THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY,

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 * OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

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 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

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 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER

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 * IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF

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 * THE POSSIBILITY OF SUCH DAMAGES.

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 */

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#ifndef	__IF_BWN_CORDIC_H__

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#define	__IF_BWN_CORDIC_H__

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/*

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 * These functions are used by the PHY code.

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 */

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/* Complex number using 2 32-bit signed integers */

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struct bwn_c32 {

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	int32_t i;

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	int32_t q;

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};

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#define	CORDIC_CONVERT(value)	(((value) >= 0) ?	\

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	    ((((value) >> 15) + 1) >> 1) :		\

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	    -((((-(value)) >> 15) + 1) >> 1))

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static const uint32_t bwn_arctg[] = {

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    2949120, 1740967, 919879, 466945, 234379, 117304, 58666, 29335, 14668,

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    7334, 3667, 1833, 917, 458, 229, 115, 57, 29,

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};

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/* http://bcm-v4.sipsolutions.net/802.11/PHY/Cordic */

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static inline struct bwn_c32

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bwn_cordic(int theta)

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{

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	uint8_t i;

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	int32_t tmp;

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	int8_t signx = 1;

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	uint32_t angle = 0;

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	struct bwn_c32 ret = { .i = 39797, .q = 0, };

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	while (theta > (180 << 16))

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		theta -= (360 << 16);

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	while (theta < -(180 << 16))

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		theta += (360 << 16);

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	if (theta > (90 << 16)) {

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		theta -= (180 << 16);

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		signx = -1;

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	} else if (theta < -(90 << 16)) {

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		theta += (180 << 16);

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		signx = -1;

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	}

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	for (i = 0; i <= 17; i++) {

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		if (theta > angle) {

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			tmp = ret.i - (ret.q >> i);

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			ret.q += ret.i >> i;

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			ret.i = tmp;

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			angle += bwn_arctg[i];

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		} else {

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			tmp = ret.i + (ret.q >> i);

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			ret.q -= ret.i >> i;

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			ret.i = tmp;

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			angle -= bwn_arctg[i];

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		}

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	}

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	ret.i *= signx;

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	ret.q *= signx;

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	return ret;

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}

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#endif	/* __IF_BWN_CORDIC_H__ */

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