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1 /* SPDX-License-Identifier: GPL-2.0-or-later */
5 #include <linux/math64.h>
8 * Simplistic fixed-point arithmetics.
9 * Hmm, I'm probably duplicating some code :(
11 * Copyright (c) 2002 Johann Deneux
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>
20 #include <linux/types.h>
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,
42 * __fixp_sin32() returns the sin of an angle in degrees
44 * @degrees: angle, in degrees, from 0 to 360.
46 * The returned value ranges from -0x7fffffff to +0x7fffffff.
48 static inline s32
__fixp_sin32(int degrees
)
51 bool negative
= false;
58 degrees
= 180 - degrees
;
60 ret
= sin_table
[degrees
];
62 return negative
? -ret
: ret
;
66 * fixp_sin32() returns the sin of an angle in degrees
68 * @degrees: angle, in degrees. The angle can be positive or negative
70 * The returned value ranges from -0x7fffffff to +0x7fffffff.
72 static inline s32
fixp_sin32(int degrees
)
74 degrees
= (degrees
% 360 + 360) % 360;
76 return __fixp_sin32(degrees
);
79 /* cos(x) = sin(x + 90 degrees) */
80 #define fixp_cos32(v) fixp_sin32((v) + 90)
85 * The returned value ranges from -0x7fff to 0x7fff
88 #define fixp_sin16(v) (fixp_sin32(v) >> 16)
89 #define fixp_cos16(v) (fixp_cos32(v) >> 16)
92 * fixp_sin32_rad() - calculates the sin of an angle in radians
94 * @radians: angle, in radians
95 * @twopi: value to be used for 2*pi
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
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.
108 * Please notice that two high numbers for twopi could cause
109 * overflows, so the routine will not allow values of twopi
112 static inline s32
fixp_sin32_rad(u32 radians
, u32 twopi
)
119 * Avoid too large values for twopi, as we don't want overflows.
121 BUG_ON(twopi
> 1 << 18);
123 degrees
= (radians
* 360) / twopi
;
124 tmp
= radians
- (degrees
* twopi
) / 360;
126 degrees
= (degrees
% 360 + 360) % 360;
127 v1
= __fixp_sin32(degrees
);
129 v2
= fixp_sin32(degrees
+ 1);
136 return v1
+ div_s64(tmp
, dx
);
139 /* cos(x) = sin(x + pi/2 radians) */
141 #define fixp_cos32_rad(rad, twopi) \
142 fixp_sin32_rad(rad + twopi / 4, twopi)