mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-11-15 00:04:15 +08:00
d89ce936b4
The code seems to provide a single function that implements the CORDIC algorithm. Signed-off-by: Michael Witten <mfwitten@gmail.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
102 lines
2.5 KiB
C
102 lines
2.5 KiB
C
/*
|
|
* Copyright (c) 2011 Broadcom Corporation
|
|
*
|
|
* Permission to use, copy, modify, and/or distribute this software for any
|
|
* purpose with or without fee is hereby granted, provided that the above
|
|
* copyright notice and this permission notice appear in all copies.
|
|
*
|
|
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
|
|
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
|
|
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
|
|
* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
|
|
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
|
|
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
|
|
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
|
|
*/
|
|
#include <linux/module.h>
|
|
#include <linux/cordic.h>
|
|
|
|
#define CORDIC_ANGLE_GEN 39797
|
|
#define CORDIC_PRECISION_SHIFT 16
|
|
#define CORDIC_NUM_ITER (CORDIC_PRECISION_SHIFT + 2)
|
|
|
|
#define FIXED(X) ((s32)((X) << CORDIC_PRECISION_SHIFT))
|
|
#define FLOAT(X) (((X) >= 0) \
|
|
? ((((X) >> (CORDIC_PRECISION_SHIFT - 1)) + 1) >> 1) \
|
|
: -((((-(X)) >> (CORDIC_PRECISION_SHIFT - 1)) + 1) >> 1))
|
|
|
|
static const s32 arctan_table[] = {
|
|
2949120,
|
|
1740967,
|
|
919879,
|
|
466945,
|
|
234379,
|
|
117304,
|
|
58666,
|
|
29335,
|
|
14668,
|
|
7334,
|
|
3667,
|
|
1833,
|
|
917,
|
|
458,
|
|
229,
|
|
115,
|
|
57,
|
|
29
|
|
};
|
|
|
|
/*
|
|
* cordic_calc_iq() - calculates the i/q coordinate for given angle
|
|
*
|
|
* theta: angle in degrees for which i/q coordinate is to be calculated
|
|
* coord: function output parameter holding the i/q coordinate
|
|
*/
|
|
struct cordic_iq cordic_calc_iq(s32 theta)
|
|
{
|
|
struct cordic_iq coord;
|
|
s32 angle, valtmp;
|
|
unsigned iter;
|
|
int signx = 1;
|
|
int signtheta;
|
|
|
|
coord.i = CORDIC_ANGLE_GEN;
|
|
coord.q = 0;
|
|
angle = 0;
|
|
|
|
theta = FIXED(theta);
|
|
signtheta = (theta < 0) ? -1 : 1;
|
|
theta = ((theta + FIXED(180) * signtheta) % FIXED(360)) -
|
|
FIXED(180) * signtheta;
|
|
|
|
if (FLOAT(theta) > 90) {
|
|
theta -= FIXED(180);
|
|
signx = -1;
|
|
} else if (FLOAT(theta) < -90) {
|
|
theta += FIXED(180);
|
|
signx = -1;
|
|
}
|
|
|
|
for (iter = 0; iter < CORDIC_NUM_ITER; iter++) {
|
|
if (theta > angle) {
|
|
valtmp = coord.i - (coord.q >> iter);
|
|
coord.q += (coord.i >> iter);
|
|
angle += arctan_table[iter];
|
|
} else {
|
|
valtmp = coord.i + (coord.q >> iter);
|
|
coord.q -= (coord.i >> iter);
|
|
angle -= arctan_table[iter];
|
|
}
|
|
coord.i = valtmp;
|
|
}
|
|
|
|
coord.i *= signx;
|
|
coord.q *= signx;
|
|
return coord;
|
|
}
|
|
EXPORT_SYMBOL(cordic_calc_iq);
|
|
|
|
MODULE_DESCRIPTION("CORDIC algorithm");
|
|
MODULE_AUTHOR("Broadcom Corporation");
|
|
MODULE_LICENSE("Dual BSD/GPL");
|