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");
102