Line data    Source code

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