1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 #ifndef _FIXP_ARITH_H
3 #define _FIXP_ARITH_H
4
5 #include <linux/math64.h>
6
7 /*
8 * Simplistic fixed-point arithmetics.
9 * Hmm, I'm probably duplicating some code :(
10 *
11 * Copyright (c) 2002 Johann Deneux
12 */
13
14 /*
15 *
16 * Should you need to contact me, the author, you can do so by
17 * e-mail - mail your message to <johann.deneux@gmail.com>
18 */
19
20 #include <linux/types.h>
21
22 static const s32 sin_table[] = {
23 0x00000000, 0x023be165, 0x04779632, 0x06b2f1d2, 0x08edc7b6, 0x0b27eb5c,
24 0x0d61304d, 0x0f996a26, 0x11d06c96, 0x14060b67, 0x163a1a7d, 0x186c6ddd,
25 0x1a9cd9ac, 0x1ccb3236, 0x1ef74bf2, 0x2120fb82, 0x234815ba, 0x256c6f9e,
26 0x278dde6e, 0x29ac379f, 0x2bc750e8, 0x2ddf003f, 0x2ff31bdd, 0x32037a44,
27 0x340ff241, 0x36185aee, 0x381c8bb5, 0x3a1c5c56, 0x3c17a4e7, 0x3e0e3ddb,
28 0x3fffffff, 0x41ecc483, 0x43d464fa, 0x45b6bb5d, 0x4793a20f, 0x496af3e1,
29 0x4b3c8c11, 0x4d084650, 0x4ecdfec6, 0x508d9210, 0x5246dd48, 0x53f9be04,
30 0x55a6125a, 0x574bb8e5, 0x58ea90c2, 0x5a827999, 0x5c135399, 0x5d9cff82,
31 0x5f1f5ea0, 0x609a52d1, 0x620dbe8a, 0x637984d3, 0x64dd894f, 0x6639b039,
32 0x678dde6d, 0x68d9f963, 0x6a1de735, 0x6b598ea1, 0x6c8cd70a, 0x6db7a879,
33 0x6ed9eba0, 0x6ff389de, 0x71046d3c, 0x720c8074, 0x730baeec, 0x7401e4bf,
34 0x74ef0ebb, 0x75d31a5f, 0x76adf5e5, 0x777f903b, 0x7847d908, 0x7906c0af,
35 0x79bc384c, 0x7a6831b8, 0x7b0a9f8c, 0x7ba3751c, 0x7c32a67c, 0x7cb82884,
36 0x7d33f0c8, 0x7da5f5a3, 0x7e0e2e31, 0x7e6c924f, 0x7ec11aa3, 0x7f0bc095,
37 0x7f4c7e52, 0x7f834ecf, 0x7fb02dc4, 0x7fd317b3, 0x7fec09e1, 0x7ffb025e,
38 0x7fffffff
39 };
40
41 /**
42 * __fixp_sin32() returns the sin of an angle in degrees
43 *
44 * @degrees: angle, in degrees, from 0 to 360.
45 *
46 * The returned value ranges from -0x7fffffff to +0x7fffffff.
47 */
__fixp_sin32(int degrees)48 static inline s32 __fixp_sin32(int degrees)
49 {
50 s32 ret;
51 bool negative = false;
52
53 if (degrees > 180) {
54 negative = true;
55 degrees -= 180;
56 }
57 if (degrees > 90)
58 degrees = 180 - degrees;
59
60 ret = sin_table[degrees];
61
62 return negative ? -ret : ret;
63 }
64
65 /**
66 * fixp_sin32() returns the sin of an angle in degrees
67 *
68 * @degrees: angle, in degrees. The angle can be positive or negative
69 *
70 * The returned value ranges from -0x7fffffff to +0x7fffffff.
71 */
fixp_sin32(int degrees)72 static inline s32 fixp_sin32(int degrees)
73 {
74 degrees = (degrees % 360 + 360) % 360;
75
76 return __fixp_sin32(degrees);
77 }
78
79 /* cos(x) = sin(x + 90 degrees) */
80 #define fixp_cos32(v) fixp_sin32((v) + 90)
81
82 /*
83 * 16 bits variants
84 *
85 * The returned value ranges from -0x7fff to 0x7fff
86 */
87
88 #define fixp_sin16(v) (fixp_sin32(v) >> 16)
89 #define fixp_cos16(v) (fixp_cos32(v) >> 16)
90
91 /**
92 * fixp_sin32_rad() - calculates the sin of an angle in radians
93 *
94 * @radians: angle, in radians
95 * @twopi: value to be used for 2*pi
96 *
97 * Provides a variant for the cases where just 360
98 * values is not enough. This function uses linear
99 * interpolation to a wider range of values given by
100 * twopi var.
101 *
102 * Experimental tests gave a maximum difference of
103 * 0.000038 between the value calculated by sin() and
104 * the one produced by this function, when twopi is
105 * equal to 360000. That seems to be enough precision
106 * for practical purposes.
107 *
108 * Please notice that two high numbers for twopi could cause
109 * overflows, so the routine will not allow values of twopi
110 * bigger than 1^18.
111 */
fixp_sin32_rad(u32 radians,u32 twopi)112 static inline s32 fixp_sin32_rad(u32 radians, u32 twopi)
113 {
114 int degrees;
115 s32 v1, v2, dx, dy;
116 s64 tmp;
117
118 /*
119 * Avoid too large values for twopi, as we don't want overflows.
120 */
121 BUG_ON(twopi > 1 << 18);
122
123 degrees = (radians * 360) / twopi;
124 tmp = radians - (degrees * twopi) / 360;
125
126 degrees = (degrees % 360 + 360) % 360;
127 v1 = __fixp_sin32(degrees);
128
129 v2 = fixp_sin32(degrees + 1);
130
131 dx = twopi / 360;
132 dy = v2 - v1;
133
134 tmp *= dy;
135
136 return v1 + div_s64(tmp, dx);
137 }
138
139 /* cos(x) = sin(x + pi/2 radians) */
140
141 #define fixp_cos32_rad(rad, twopi) \
142 fixp_sin32_rad(rad + twopi / 4, twopi)
143
144 /**
145 * fixp_linear_interpolate() - interpolates a value from two known points
146 *
147 * @x0: x value of point 0
148 * @y0: y value of point 0
149 * @x1: x value of point 1
150 * @y1: y value of point 1
151 * @x: the linear interpolant
152 */
fixp_linear_interpolate(int x0,int y0,int x1,int y1,int x)153 static inline int fixp_linear_interpolate(int x0, int y0, int x1, int y1, int x)
154 {
155 if (y0 == y1 || x == x0)
156 return y0;
157 if (x1 == x0 || x == x1)
158 return y1;
159
160 return y0 + ((y1 - y0) * (x - x0) / (x1 - x0));
161 }
162
163 #endif
164