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authorArend van Spriel <arend@broadcom.com>2011-05-31 11:22:16 +0200
committerJohn W. Linville <linville@tuxdriver.com>2011-06-03 15:01:07 -0400
commit10f8113ecb76eea72f96c7cfb72d7fed7c282565 (patch)
tree85dd734aeee52e3f21851f11436f4dabaf130033 /lib/cordic.c
parent7150962d637cf38617924f7f72ea00612283eb89 (diff)
downloadlinux-stericsson-10f8113ecb76eea72f96c7cfb72d7fed7c282565.tar.gz
lib: cordic: add library module providing cordic angle calculation
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>
Diffstat (limited to 'lib/cordic.c')
-rw-r--r--lib/cordic.c101
1 files changed, 101 insertions, 0 deletions
diff --git a/lib/cordic.c b/lib/cordic.c
new file mode 100644
index 000000000000..aa27a88d7e04
--- /dev/null
+++ b/lib/cordic.c
@@ -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");