[bwn] add an implementation of "cordic" and imaginary math.

This is used by the PHY-N code. Obtained from: http://bcm-v4.sipsolutions.net/802.11/PHY/Cordic
2016-05-14 23:33:13 +00:00 · 2016-05-14 23:33:13 +00:00 · 98110a9482
commit 98110a9482
parent e5af8e55f1
1 changed files with 96 additions and 0 deletions
--- a/sys/dev/bwn/if_bwn_cordic.h
+++ b/sys/dev/bwn/if_bwn_cordic.h
@ -0,0 +1,96 @@
+/*-
+ * Copyright (c) 2016 Adrian Chadd <adrian@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer,
+ *    without modification.
+ * 2. Redistributions in binary form must reproduce at minimum a disclaimer
+ *    similar to the "NO WARRANTY" disclaimer below ("Disclaimer") and any
+ *    redistribution must be conditioned upon including a substantially
+ *    similar Disclaimer requirement for further binary redistribution.
+ *
+ * NO WARRANTY
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF NONINFRINGEMENT, MERCHANTIBILITY
+ * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY,
+ * OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
+ * IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ * THE POSSIBILITY OF SUCH DAMAGES.
+ *
+ * $FreeBSD$
+ */
+#ifndef	__IF_BWN_CORDIC_H__
+#define	__IF_BWN_CORDIC_H__
+
+/*
+ * These functions are used by the PHY code.
+ */
+
+/* Complex number using 2 32-bit signed integers */
+struct bwn_c32 {
+	int32_t i;
+	int32_t q;
+};
+
+#define	CORDIC_CONVERT(value)	(((value) >= 0) ?	\
+	    ((((value) >> 15) + 1) >> 1) :		\
+	    -((((-(value)) >> 15) + 1) >> 1))
+
+static const uint32_t bwn_arctg[] = {
+    2949120, 1740967, 919879, 466945, 234379, 117304, 58666, 29335, 14668,
+    7334, 3667, 1833, 917, 458, 229, 115, 57, 29,
+};
+
+/* http://bcm-v4.sipsolutions.net/802.11/PHY/Cordic */
+static inline struct bwn_c32
+bwn_cordic(int theta)
+{
+	uint8_t i;
+	int32_t tmp;
+	int8_t signx = 1;
+	uint32_t angle = 0;
+	struct bwn_c32 ret = { .i = 39797, .q = 0, };
+
+	while (theta > (180 << 16))
+		theta -= (360 << 16);
+	while (theta < -(180 << 16))
+		theta += (360 << 16);
+
+	if (theta > (90 << 16)) {
+		theta -= (180 << 16);
+		signx = -1;
+	} else if (theta < -(90 << 16)) {
+		theta += (180 << 16);
+		signx = -1;
+	}
+
+	for (i = 0; i <= 17; i++) {
+		if (theta > angle) {
+			tmp = ret.i - (ret.q >> i);
+			ret.q += ret.i >> i;
+			ret.i = tmp;
+			angle += bwn_arctg[i];
+		} else {
+			tmp = ret.i + (ret.q >> i);
+			ret.q -= ret.i >> i;
+			ret.i = tmp;
+			angle -= bwn_arctg[i];
+		}
+	}
+
+	ret.i *= signx;
+	ret.q *= signx;
+
+	return ret;
+}
+
+#endif	/* __IF_BWN_CORDIC_H__ */