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 static const s32 arctan_table[] = {
20 2949120,
21 1740967,
22 919879,
23 466945,
24 234379,
25 117304,
26 58666,
27 29335,
28 14668,
29 7334,
30 3667,
31 1833,
32 917,
33 458,
34 229,
35 115,
36 57,
37 29
38 };
39
40 /*
41 * cordic_calc_iq() - calculates the i/q coordinate for given angle
42 *
43 * theta: angle in degrees for which i/q coordinate is to be calculated
44 * coord: function output parameter holding the i/q coordinate
45 */
cordic_calc_iq(s32 theta)46 struct cordic_iq cordic_calc_iq(s32 theta)
47 {
48 struct cordic_iq coord;
49 s32 angle, valtmp;
50 unsigned iter;
51 int signx = 1;
52 int signtheta;
53
54 coord.i = CORDIC_ANGLE_GEN;
55 coord.q = 0;
56 angle = 0;
57
58 theta = CORDIC_FIXED(theta);
59 signtheta = (theta < 0) ? -1 : 1;
60 theta = ((theta + CORDIC_FIXED(180) * signtheta) % CORDIC_FIXED(360)) -
61 CORDIC_FIXED(180) * signtheta;
62
63 if (CORDIC_FLOAT(theta) > 90) {
64 theta -= CORDIC_FIXED(180);
65 signx = -1;
66 } else if (CORDIC_FLOAT(theta) < -90) {
67 theta += CORDIC_FIXED(180);
68 signx = -1;
69 }
70
71 for (iter = 0; iter < CORDIC_NUM_ITER; iter++) {
72 if (theta > angle) {
73 valtmp = coord.i - (coord.q >> iter);
74 coord.q += (coord.i >> iter);
75 angle += arctan_table[iter];
76 } else {
77 valtmp = coord.i + (coord.q >> iter);
78 coord.q -= (coord.i >> iter);
79 angle -= arctan_table[iter];
80 }
81 coord.i = valtmp;
82 }
83
84 coord.i *= signx;
85 coord.q *= signx;
86 return coord;
87 }
88 EXPORT_SYMBOL(cordic_calc_iq);
89
90 MODULE_DESCRIPTION("CORDIC algorithm");
91 MODULE_AUTHOR("Broadcom Corporation");
92 MODULE_LICENSE("Dual BSD/GPL");
93