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lib: cordic: add library module providing cordic angle calculation

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The brcm80211 driver in the staging tree has a cordic function to
determine cosine and sine for a given angle. Feedback received from
John Linville suggested that these kind of functions should be made
available to others as a library function in the kernel tree. The
b43 driver also has a cordic angle calculation implemented.

Cc: linux-kernel@vger.kernel.org
Cc: linux-wireless@vger.kernel.org
Cc: "John W. Linville" <linville@tuxdriver.com>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Dan Carpenter <error27@gmail.com>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Cc: Larry Finger <Larry.Finger@lwfinger.net>
Reviewed-by: Roland Vossen <rvossen@broadcom.com>
Reviewed-by: Henry Ptasinski <henryp@broadcom.com>
Reviewed-by: Franky (Zhenhui) Lin <frankyl@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This commit is contained in:
Arend van Spriel 2011-05-31 11:22:16 +02:00 • committed by John W. Linville
parent 7150962d63
commit 10f8113ecb
4 changed files with 158 additions and 0 deletions
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101
lib/cordic.c Normal file
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/*
* 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 functions");
MODULE_AUTHOR("Broadcom Corporation");
MODULE_LICENSE("Dual BSD/GPL");