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
28 static 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 */
cordic_calc_iq(s32 theta)55 struct 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 }
97 EXPORT_SYMBOL(cordic_calc_iq);
98
99 MODULE_DESCRIPTION("CORDIC algorithm");
100 MODULE_AUTHOR("Broadcom Corporation");
101 MODULE_LICENSE("Dual BSD/GPL");
102