1/*
  2 * Copyright (c) 2011 Broadcom Corporation
  3 *
  4 * Permission to use, copy, modify, and/or distribute this software for any
  5 * purpose with or without fee is hereby granted, provided that the above
  6 * copyright notice and this permission notice appear in all copies.
  7 *
  8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 11 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
 13 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 14 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 15 */
 16#include <linux/module.h>
 17#include <linux/cordic.h>
 18
 19#define CORDIC_ANGLE_GEN	39797
 20#define CORDIC_PRECISION_SHIFT	16
 21#define	CORDIC_NUM_ITER		(CORDIC_PRECISION_SHIFT + 2)
 22
 23#define	FIXED(X)	((s32)((X) << CORDIC_PRECISION_SHIFT))
 24#define	FLOAT(X)	(((X) >= 0) \
 25		? ((((X) >> (CORDIC_PRECISION_SHIFT - 1)) + 1) >> 1) \
 26		: -((((-(X)) >> (CORDIC_PRECISION_SHIFT - 1)) + 1) >> 1))
 27
 28static const s32 arctan_table[] = {
 29	2949120,
 30	1740967,
 31	919879,
 32	466945,
 33	234379,
 34	117304,
 35	58666,
 36	29335,
 37	14668,
 38	7334,
 39	3667,
 40	1833,
 41	917,
 42	458,
 43	229,
 44	115,
 45	57,
 46	29
 47};
 48
 49/*
 50 * cordic_calc_iq() - calculates the i/q coordinate for given angle
 51 *
 52 * theta: angle in degrees for which i/q coordinate is to be calculated
 53 * coord: function output parameter holding the i/q coordinate
 54 */
 55struct cordic_iq cordic_calc_iq(s32 theta)
 56{
 57	struct cordic_iq coord;
 58	s32 angle, valtmp;
 59	unsigned iter;
 60	int signx = 1;
 61	int signtheta;
 62
 63	coord.i = CORDIC_ANGLE_GEN;
 64	coord.q = 0;
 65	angle = 0;
 66
 67	theta = FIXED(theta);
 68	signtheta = (theta < 0) ? -1 : 1;
 69	theta = ((theta + FIXED(180) * signtheta) % FIXED(360)) -
 70		FIXED(180) * signtheta;
 71
 72	if (FLOAT(theta) > 90) {
 73		theta -= FIXED(180);
 74		signx = -1;
 75	} else if (FLOAT(theta) < -90) {
 76		theta += FIXED(180);
 77		signx = -1;
 78	}
 79
 80	for (iter = 0; iter < CORDIC_NUM_ITER; iter++) {
 81		if (theta > angle) {
 82			valtmp = coord.i - (coord.q >> iter);
 83			coord.q += (coord.i >> iter);
 84			angle += arctan_table[iter];
 85		} else {
 86			valtmp = coord.i + (coord.q >> iter);
 87			coord.q -= (coord.i >> iter);
 88			angle -= arctan_table[iter];
 89		}
 90		coord.i = valtmp;
 91	}
 92
 93	coord.i *= signx;
 94	coord.q *= signx;
 95	return coord;
 96}
 97EXPORT_SYMBOL(cordic_calc_iq);
 98
 99MODULE_DESCRIPTION("CORDIC algorithm");
100MODULE_AUTHOR("Broadcom Corporation");
101MODULE_LICENSE("Dual BSD/GPL");