linux/include/drm/drm_fixed.h
<<
>>
Prefs
   1/*
   2 * Copyright 2009 Red Hat Inc.
   3 *
   4 * Permission is hereby granted, free of charge, to any person obtaining a
   5 * copy of this software and associated documentation files (the "Software"),
   6 * to deal in the Software without restriction, including without limitation
   7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8 * and/or sell copies of the Software, and to permit persons to whom the
   9 * Software is furnished to do so, subject to the following conditions:
  10 *
  11 * The above copyright notice and this permission notice shall be included in
  12 * all copies or substantial portions of the Software.
  13 *
  14 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  15 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  16 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  17 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
  18 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  19 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  20 * OTHER DEALINGS IN THE SOFTWARE.
  21 *
  22 * Authors: Dave Airlie
  23 *          Christian K├Ânig
  24 */
  25#ifndef DRM_FIXED_H
  26#define DRM_FIXED_H
  27
  28#include <linux/math64.h>
  29
  30typedef union dfixed {
  31        u32 full;
  32} fixed20_12;
  33
  34
  35#define dfixed_const(A) (u32)(((A) << 12))/*  + ((B + 0.000122)*4096)) */
  36#define dfixed_const_half(A) (u32)(((A) << 12) + 2048)
  37#define dfixed_const_666(A) (u32)(((A) << 12) + 2731)
  38#define dfixed_const_8(A) (u32)(((A) << 12) + 3277)
  39#define dfixed_mul(A, B) ((u64)((u64)(A).full * (B).full + 2048) >> 12)
  40#define dfixed_init(A) { .full = dfixed_const((A)) }
  41#define dfixed_init_half(A) { .full = dfixed_const_half((A)) }
  42#define dfixed_trunc(A) ((A).full >> 12)
  43#define dfixed_frac(A) ((A).full & ((1 << 12) - 1))
  44
  45static inline u32 dfixed_floor(fixed20_12 A)
  46{
  47        u32 non_frac = dfixed_trunc(A);
  48
  49        return dfixed_const(non_frac);
  50}
  51
  52static inline u32 dfixed_ceil(fixed20_12 A)
  53{
  54        u32 non_frac = dfixed_trunc(A);
  55
  56        if (A.full > dfixed_const(non_frac))
  57                return dfixed_const(non_frac + 1);
  58        else
  59                return dfixed_const(non_frac);
  60}
  61
  62static inline u32 dfixed_div(fixed20_12 A, fixed20_12 B)
  63{
  64        u64 tmp = ((u64)A.full << 13);
  65
  66        do_div(tmp, B.full);
  67        tmp += 1;
  68        tmp /= 2;
  69        return lower_32_bits(tmp);
  70}
  71
  72#define DRM_FIXED_POINT         32
  73#define DRM_FIXED_ONE           (1ULL << DRM_FIXED_POINT)
  74#define DRM_FIXED_DECIMAL_MASK  (DRM_FIXED_ONE - 1)
  75#define DRM_FIXED_DIGITS_MASK   (~DRM_FIXED_DECIMAL_MASK)
  76#define DRM_FIXED_EPSILON       1LL
  77#define DRM_FIXED_ALMOST_ONE    (DRM_FIXED_ONE - DRM_FIXED_EPSILON)
  78
  79static inline s64 drm_int2fixp(int a)
  80{
  81        return ((s64)a) << DRM_FIXED_POINT;
  82}
  83
  84static inline int drm_fixp2int(s64 a)
  85{
  86        return ((s64)a) >> DRM_FIXED_POINT;
  87}
  88
  89static inline int drm_fixp2int_ceil(s64 a)
  90{
  91        if (a > 0)
  92                return drm_fixp2int(a + DRM_FIXED_ALMOST_ONE);
  93        else
  94                return drm_fixp2int(a - DRM_FIXED_ALMOST_ONE);
  95}
  96
  97static inline unsigned drm_fixp_msbset(s64 a)
  98{
  99        unsigned shift, sign = (a >> 63) & 1;
 100
 101        for (shift = 62; shift > 0; --shift)
 102                if (((a >> shift) & 1) != sign)
 103                        return shift;
 104
 105        return 0;
 106}
 107
 108static inline s64 drm_fixp_mul(s64 a, s64 b)
 109{
 110        unsigned shift = drm_fixp_msbset(a) + drm_fixp_msbset(b);
 111        s64 result;
 112
 113        if (shift > 61) {
 114                shift = shift - 61;
 115                a >>= (shift >> 1) + (shift & 1);
 116                b >>= shift >> 1;
 117        } else
 118                shift = 0;
 119
 120        result = a * b;
 121
 122        if (shift > DRM_FIXED_POINT)
 123                return result << (shift - DRM_FIXED_POINT);
 124
 125        if (shift < DRM_FIXED_POINT)
 126                return result >> (DRM_FIXED_POINT - shift);
 127
 128        return result;
 129}
 130
 131static inline s64 drm_fixp_div(s64 a, s64 b)
 132{
 133        unsigned shift = 62 - drm_fixp_msbset(a);
 134        s64 result;
 135
 136        a <<= shift;
 137
 138        if (shift < DRM_FIXED_POINT)
 139                b >>= (DRM_FIXED_POINT - shift);
 140
 141        result = div64_s64(a, b);
 142
 143        if (shift > DRM_FIXED_POINT)
 144                return result >> (shift - DRM_FIXED_POINT);
 145
 146        return result;
 147}
 148
 149static inline s64 drm_fixp_from_fraction(s64 a, s64 b)
 150{
 151        s64 res;
 152        bool a_neg = a < 0;
 153        bool b_neg = b < 0;
 154        u64 a_abs = a_neg ? -a : a;
 155        u64 b_abs = b_neg ? -b : b;
 156        u64 rem;
 157
 158        /* determine integer part */
 159        u64 res_abs  = div64_u64_rem(a_abs, b_abs, &rem);
 160
 161        /* determine fractional part */
 162        {
 163                u32 i = DRM_FIXED_POINT;
 164
 165                do {
 166                        rem <<= 1;
 167                        res_abs <<= 1;
 168                        if (rem >= b_abs) {
 169                                res_abs |= 1;
 170                                rem -= b_abs;
 171                        }
 172                } while (--i != 0);
 173        }
 174
 175        /* round up LSB */
 176        {
 177                u64 summand = (rem << 1) >= b_abs;
 178
 179                res_abs += summand;
 180        }
 181
 182        res = (s64) res_abs;
 183        if (a_neg ^ b_neg)
 184                res = -res;
 185        return res;
 186}
 187
 188static inline s64 drm_fixp_exp(s64 x)
 189{
 190        s64 tolerance = div64_s64(DRM_FIXED_ONE, 1000000);
 191        s64 sum = DRM_FIXED_ONE, term, y = x;
 192        u64 count = 1;
 193
 194        if (x < 0)
 195                y = -1 * x;
 196
 197        term = y;
 198
 199        while (term >= tolerance) {
 200                sum = sum + term;
 201                count = count + 1;
 202                term = drm_fixp_mul(term, div64_s64(y, count));
 203        }
 204
 205        if (x < 0)
 206                sum = drm_fixp_div(DRM_FIXED_ONE, sum);
 207
 208        return sum;
 209}
 210
 211#endif
 212