lib/cordic.c

   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  */
  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");