include/drm/drm_fixed.h

   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 König
  24  */
  25 #ifndef DRM_FIXED_H
  26 #define DRM_FIXED_H
  27
  28 #include <linux/math64.h>
  29
  30 typedef 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
  45 static inline u32 dfixed_floor(fixed20_12 A)
  46 {
  47         u32 non_frac = dfixed_trunc(A);
  48
  49         return dfixed_const(non_frac);
  50 }
  51
  52 static 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
  62 static 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
  79 static inline s64 drm_int2fixp(int a)
  80 {
  81         return ((s64)a) << DRM_FIXED_POINT;
  82 }
  83
  84 static inline int drm_fixp2int(s64 a)
  85 {
  86         return ((s64)a) >> DRM_FIXED_POINT;
  87 }
  88
  89 static 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
  97 static 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
 108 static 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
 131 static 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
 149 static 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
 188 static 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