diff options
| -rw-r--r-- | include/linux/cordic.h | 48 | ||||
| -rw-r--r-- | lib/Kconfig | 7 | ||||
| -rw-r--r-- | lib/Makefile | 2 | ||||
| -rw-r--r-- | lib/cordic.c | 101 |
4 files changed, 158 insertions, 0 deletions
diff --git a/include/linux/cordic.h b/include/linux/cordic.h new file mode 100644 index 00000000000..f932093e20c --- /dev/null +++ b/include/linux/cordic.h @@ -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_ */ diff --git a/lib/Kconfig b/lib/Kconfig index ff9e5a34be7..5c702047c57 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -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 diff --git a/lib/Makefile b/lib/Makefile index 704959d2018..9e3c1b0652d 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -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 diff --git a/lib/cordic.c b/lib/cordic.c new file mode 100644 index 00000000000..aa27a88d7e0 --- /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"); |