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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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48
include/linux/cordic.h Normal file
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@ -0,0 +1,48 @@
/*
* 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.
*/
#ifndef __CORDIC_H_
#define __CORDIC_H_
#include <linux/types.h>
/**
* struct cordic_iq - i/q coordinate.
*
* @i: real part of coordinate (in phase).
* @q: imaginary part of coordinate (quadrature).
*/
struct cordic_iq {
s32 i;
s32 q;
};
/**
* 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.
*
* The function calculates the i/q coordinate for a given angle using
* cordic algorithm. The coordinate consists of a real (i) and an
* imaginary (q) part. The real part is essentially the cosine of the
* angle and the imaginary part is the sine of the angle. The returned
* values are scaled by 2^16 for precision. The range for theta is
* for -180 degrees to +180 degrees. Passed values outside this range are
* converted before doing the actual calculation.
*/
struct cordic_iq cordic_calc_iq(s32 theta);
#endif /* __CORDIC_H_ */

7
lib/Kconfig
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@ -279,4 +279,11 @@ config AVERAGE
If unsure, say N.
config CORDIC
tristate "Cordic function"
help
The option provides arithmetic function using cordic algorithm
so its calculations are in fixed point. Modules can select this
when they require this function. Module will be called cordic.
endmenu

2
lib/Makefile
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@ -117,6 +117,8 @@ obj-$(CONFIG_AVERAGE) += average.o
obj-$(CONFIG_CPU_RMAP) += cpu_rmap.o
obj-$(CONFIG_CORDIC) += cordic.o
hostprogs-y := gen_crc32table
clean-files := crc32table.h

101
lib/cordic.c Normal file
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@ -0,0 +1,101 @@
/*
* 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");