lib: cordic: add library module providing cordic angle calculation

[~andy/linux] / lib / cordic.c

diff --git a/lib/cordic.c b/lib/cordic.c
new file mode 100644 (file)
index 0000000..aa27a88
--- /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");