include/drm/drm_fixed.h

0001 /*
0002  * Copyright 2009 Red Hat Inc.
0003  *
0004  * Permission is hereby granted, free of charge, to any person obtaining a
0005  * copy of this software and associated documentation files (the "Software"),
0006  * to deal in the Software without restriction, including without limitation
0007  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
0008  * and/or sell copies of the Software, and to permit persons to whom the
0009  * Software is furnished to do so, subject to the following conditions:
0010  *
0011  * The above copyright notice and this permission notice shall be included in
0012  * all copies or substantial portions of the Software.
0013  *
0014  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
0015  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
0016  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
0017  * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
0018  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
0019  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
0020  * OTHER DEALINGS IN THE SOFTWARE.
0021  *
0022  * Authors: Dave Airlie
0023  *          Christian König
0024  */
0025 #ifndef DRM_FIXED_H
0026 #define DRM_FIXED_H
0027
0028 #include <linux/math64.h>
0029
0030 typedef union dfixed {
0031     u32 full;
0032 } fixed20_12;
0033
0034
0035 #define dfixed_const(A) (u32)(((A) << 12))/*  + ((B + 0.000122)*4096)) */
0036 #define dfixed_const_half(A) (u32)(((A) << 12) + 2048)
0037 #define dfixed_const_666(A) (u32)(((A) << 12) + 2731)
0038 #define dfixed_const_8(A) (u32)(((A) << 12) + 3277)
0039 #define dfixed_mul(A, B) ((u64)((u64)(A).full * (B).full + 2048) >> 12)
0040 #define dfixed_init(A) { .full = dfixed_const((A)) }
0041 #define dfixed_init_half(A) { .full = dfixed_const_half((A)) }
0042 #define dfixed_trunc(A) ((A).full >> 12)
0043 #define dfixed_frac(A) ((A).full & ((1 << 12) - 1))
0044
0045 static inline u32 dfixed_floor(fixed20_12 A)
0046 {
0047     u32 non_frac = dfixed_trunc(A);
0048
0049     return dfixed_const(non_frac);
0050 }
0051
0052 static inline u32 dfixed_ceil(fixed20_12 A)
0053 {
0054     u32 non_frac = dfixed_trunc(A);
0055
0056     if (A.full > dfixed_const(non_frac))
0057         return dfixed_const(non_frac + 1);
0058     else
0059         return dfixed_const(non_frac);
0060 }
0061
0062 static inline u32 dfixed_div(fixed20_12 A, fixed20_12 B)
0063 {
0064     u64 tmp = ((u64)A.full << 13);
0065
0066     do_div(tmp, B.full);
0067     tmp += 1;
0068     tmp /= 2;
0069     return lower_32_bits(tmp);
0070 }
0071
0072 #define DRM_FIXED_POINT     32
0073 #define DRM_FIXED_ONE       (1ULL << DRM_FIXED_POINT)
0074 #define DRM_FIXED_DECIMAL_MASK  (DRM_FIXED_ONE - 1)
0075 #define DRM_FIXED_DIGITS_MASK   (~DRM_FIXED_DECIMAL_MASK)
0076 #define DRM_FIXED_EPSILON   1LL
0077 #define DRM_FIXED_ALMOST_ONE    (DRM_FIXED_ONE - DRM_FIXED_EPSILON)
0078
0079 static inline s64 drm_int2fixp(int a)
0080 {
0081     return ((s64)a) << DRM_FIXED_POINT;
0082 }
0083
0084 static inline int drm_fixp2int(s64 a)
0085 {
0086     return ((s64)a) >> DRM_FIXED_POINT;
0087 }
0088
0089 static inline int drm_fixp2int_ceil(s64 a)
0090 {
0091     if (a > 0)
0092         return drm_fixp2int(a + DRM_FIXED_ALMOST_ONE);
0093     else
0094         return drm_fixp2int(a - DRM_FIXED_ALMOST_ONE);
0095 }
0096
0097 static inline unsigned drm_fixp_msbset(s64 a)
0098 {
0099     unsigned shift, sign = (a >> 63) & 1;
0100
0101     for (shift = 62; shift > 0; --shift)
0102         if (((a >> shift) & 1) != sign)
0103             return shift;
0104
0105     return 0;
0106 }
0107
0108 static inline s64 drm_fixp_mul(s64 a, s64 b)
0109 {
0110     unsigned shift = drm_fixp_msbset(a) + drm_fixp_msbset(b);
0111     s64 result;
0112
0113     if (shift > 61) {
0114         shift = shift - 61;
0115         a >>= (shift >> 1) + (shift & 1);
0116         b >>= shift >> 1;
0117     } else
0118         shift = 0;
0119
0120     result = a * b;
0121
0122     if (shift > DRM_FIXED_POINT)
0123         return result << (shift - DRM_FIXED_POINT);
0124
0125     if (shift < DRM_FIXED_POINT)
0126         return result >> (DRM_FIXED_POINT - shift);
0127
0128     return result;
0129 }
0130
0131 static inline s64 drm_fixp_div(s64 a, s64 b)
0132 {
0133     unsigned shift = 62 - drm_fixp_msbset(a);
0134     s64 result;
0135
0136     a <<= shift;
0137
0138     if (shift < DRM_FIXED_POINT)
0139         b >>= (DRM_FIXED_POINT - shift);
0140
0141     result = div64_s64(a, b);
0142
0143     if (shift > DRM_FIXED_POINT)
0144         return result >> (shift - DRM_FIXED_POINT);
0145
0146     return result;
0147 }
0148
0149 static inline s64 drm_fixp_from_fraction(s64 a, s64 b)
0150 {
0151     s64 res;
0152     bool a_neg = a < 0;
0153     bool b_neg = b < 0;
0154     u64 a_abs = a_neg ? -a : a;
0155     u64 b_abs = b_neg ? -b : b;
0156     u64 rem;
0157
0158     /* determine integer part */
0159     u64 res_abs  = div64_u64_rem(a_abs, b_abs, &rem);
0160
0161     /* determine fractional part */
0162     {
0163         u32 i = DRM_FIXED_POINT;
0164
0165         do {
0166             rem <<= 1;
0167             res_abs <<= 1;
0168             if (rem >= b_abs) {
0169                 res_abs |= 1;
0170                 rem -= b_abs;
0171             }
0172         } while (--i != 0);
0173     }
0174
0175     /* round up LSB */
0176     {
0177         u64 summand = (rem << 1) >= b_abs;
0178
0179         res_abs += summand;
0180     }
0181
0182     res = (s64) res_abs;
0183     if (a_neg ^ b_neg)
0184         res = -res;
0185     return res;
0186 }
0187
0188 static inline s64 drm_fixp_exp(s64 x)
0189 {
0190     s64 tolerance = div64_s64(DRM_FIXED_ONE, 1000000);
0191     s64 sum = DRM_FIXED_ONE, term, y = x;
0192     u64 count = 1;
0193
0194     if (x < 0)
0195         y = -1 * x;
0196
0197     term = y;
0198
0199     while (term >= tolerance) {
0200         sum = sum + term;
0201         count = count + 1;
0202         term = drm_fixp_mul(term, div64_s64(y, count));
0203     }
0204
0205     if (x < 0)
0206         sum = drm_fixp_div(DRM_FIXED_ONE, sum);
0207
0208     return sum;
0209 }
0210
0211 #endif