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/kernel.h>
29#include <linux/math64.h>
30
31typedef union dfixed {
32 u32 full;
33} fixed20_12;
34
35
36#define dfixed_const(A) (u32)(((A) << 12))/* + ((B + 0.000122)*4096)) */
37#define dfixed_const_half(A) (u32)(((A) << 12) + 2048)
38#define dfixed_const_666(A) (u32)(((A) << 12) + 2731)
39#define dfixed_const_8(A) (u32)(((A) << 12) + 3277)
40#define dfixed_mul(A, B) ((u64)((u64)(A).full * (B).full + 2048) >> 12)
41#define dfixed_init(A) { .full = dfixed_const((A)) }
42#define dfixed_init_half(A) { .full = dfixed_const_half((A)) }
43#define dfixed_trunc(A) ((A).full >> 12)
44#define dfixed_frac(A) ((A).full & ((1 << 12) - 1))
45
46static inline u32 dfixed_floor(fixed20_12 A)
47{
48 u32 non_frac = dfixed_trunc(A);
49
50 return dfixed_const(non_frac);
51}
52
53static inline u32 dfixed_ceil(fixed20_12 A)
54{
55 u32 non_frac = dfixed_trunc(A);
56
57 if (A.full > dfixed_const(non_frac))
58 return dfixed_const(non_frac + 1);
59 else
60 return dfixed_const(non_frac);
61}
62
63static inline u32 dfixed_div(fixed20_12 A, fixed20_12 B)
64{
65 u64 tmp = ((u64)A.full << 13);
66
67 do_div(tmp, B.full);
68 tmp += 1;
69 tmp /= 2;
70 return lower_32_bits(tmp);
71}
72
73#define DRM_FIXED_POINT 32
74#define DRM_FIXED_ONE (1ULL << DRM_FIXED_POINT)
75#define DRM_FIXED_DECIMAL_MASK (DRM_FIXED_ONE - 1)
76#define DRM_FIXED_DIGITS_MASK (~DRM_FIXED_DECIMAL_MASK)
77#define DRM_FIXED_EPSILON 1LL
78#define DRM_FIXED_ALMOST_ONE (DRM_FIXED_ONE - DRM_FIXED_EPSILON)
79
80static inline s64 drm_int2fixp(int a)
81{
82 return ((s64)a) << DRM_FIXED_POINT;
83}
84
85static inline int drm_fixp2int(s64 a)
86{
87 return ((s64)a) >> DRM_FIXED_POINT;
88}
89
90static inline int drm_fixp2int_round(s64 a)
91{
92 return drm_fixp2int(a: a + DRM_FIXED_ONE / 2);
93}
94
95static inline int drm_fixp2int_ceil(s64 a)
96{
97 if (a >= 0)
98 return drm_fixp2int(a: a + DRM_FIXED_ALMOST_ONE);
99 else
100 return drm_fixp2int(a: a - DRM_FIXED_ALMOST_ONE);
101}
102
103static inline unsigned drm_fixp_msbset(s64 a)
104{
105 unsigned shift, sign = (a >> 63) & 1;
106
107 for (shift = 62; shift > 0; --shift)
108 if (((a >> shift) & 1) != sign)
109 return shift;
110
111 return 0;
112}
113
114static inline s64 drm_fixp_mul(s64 a, s64 b)
115{
116 unsigned shift = drm_fixp_msbset(a) + drm_fixp_msbset(a: b);
117 s64 result;
118
119 if (shift > 61) {
120 shift = shift - 61;
121 a >>= (shift >> 1) + (shift & 1);
122 b >>= shift >> 1;
123 } else
124 shift = 0;
125
126 result = a * b;
127
128 if (shift > DRM_FIXED_POINT)
129 return result << (shift - DRM_FIXED_POINT);
130
131 if (shift < DRM_FIXED_POINT)
132 return result >> (DRM_FIXED_POINT - shift);
133
134 return result;
135}
136
137static inline s64 drm_fixp_div(s64 a, s64 b)
138{
139 unsigned shift = 62 - drm_fixp_msbset(a);
140 s64 result;
141
142 a <<= shift;
143
144 if (shift < DRM_FIXED_POINT)
145 b >>= (DRM_FIXED_POINT - shift);
146
147 result = div64_s64(dividend: a, divisor: b);
148
149 if (shift > DRM_FIXED_POINT)
150 return result >> (shift - DRM_FIXED_POINT);
151
152 return result;
153}
154
155static inline s64 drm_fixp_from_fraction(s64 a, s64 b)
156{
157 s64 res;
158 bool a_neg = a < 0;
159 bool b_neg = b < 0;
160 u64 a_abs = a_neg ? -a : a;
161 u64 b_abs = b_neg ? -b : b;
162 u64 rem;
163
164 /* determine integer part */
165 u64 res_abs = div64_u64_rem(dividend: a_abs, divisor: b_abs, remainder: &rem);
166
167 /* determine fractional part */
168 {
169 u32 i = DRM_FIXED_POINT;
170
171 do {
172 rem <<= 1;
173 res_abs <<= 1;
174 if (rem >= b_abs) {
175 res_abs |= 1;
176 rem -= b_abs;
177 }
178 } while (--i != 0);
179 }
180
181 /* round up LSB */
182 {
183 u64 summand = (rem << 1) >= b_abs;
184
185 res_abs += summand;
186 }
187
188 res = (s64) res_abs;
189 if (a_neg ^ b_neg)
190 res = -res;
191 return res;
192}
193
194static inline s64 drm_fixp_exp(s64 x)
195{
196 s64 tolerance = div64_s64(DRM_FIXED_ONE, divisor: 1000000);
197 s64 sum = DRM_FIXED_ONE, term, y = x;
198 u64 count = 1;
199
200 if (x < 0)
201 y = -1 * x;
202
203 term = y;
204
205 while (term >= tolerance) {
206 sum = sum + term;
207 count = count + 1;
208 term = drm_fixp_mul(a: term, b: div64_s64(dividend: y, divisor: count));
209 }
210
211 if (x < 0)
212 sum = drm_fixp_div(DRM_FIXED_ONE, b: sum);
213
214 return sum;
215}
216
217#endif
218

source code of linux/include/drm/drm_fixed.h