1 /* $NetBSD: drm_fixed.h,v 1.4 2021/12/18 23:45:46 riastradh Exp $ */
2
3 /*
4 * Copyright 2009 Red Hat Inc.
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a
7 * copy of this software and associated documentation files (the "Software"),
8 * to deal in the Software without restriction, including without limitation
9 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
10 * and/or sell copies of the Software, and to permit persons to whom the
11 * Software is furnished to do so, subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
19 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
20 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
21 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
22 * OTHER DEALINGS IN THE SOFTWARE.
23 *
24 * Authors: Dave Airlie
25 * Christian König
26 */
27 #ifndef DRM_FIXED_H
28 #define DRM_FIXED_H
29
30 #include <linux/math64.h>
31
32 typedef union dfixed {
33 u32 full;
34 } fixed20_12;
35
36
37 #define dfixed_const(A) (((u32)(A) << 12))/* + ((B + 0.000122)*4096)) */
38 #define dfixed_const_half(A) (u32)(((A) << 12) + 2048)
39 #define dfixed_const_666(A) (u32)(((A) << 12) + 2731)
40 #define dfixed_const_8(A) (u32)(((A) << 12) + 3277)
41 #define dfixed_mul(A, B) ((u64)((u64)(A).full * (B).full + 2048) >> 12)
42 #define dfixed_init(A) { .full = dfixed_const((A)) }
43 #define dfixed_init_half(A) { .full = dfixed_const_half((A)) }
44 #define dfixed_trunc(A) ((A).full >> 12)
45 #define dfixed_frac(A) ((A).full & ((1 << 12) - 1))
46
dfixed_floor(fixed20_12 A)47 static inline u32 dfixed_floor(fixed20_12 A)
48 {
49 u32 non_frac = dfixed_trunc(A);
50
51 return dfixed_const(non_frac);
52 }
53
dfixed_ceil(fixed20_12 A)54 static inline u32 dfixed_ceil(fixed20_12 A)
55 {
56 u32 non_frac = dfixed_trunc(A);
57
58 if (A.full > dfixed_const(non_frac))
59 return dfixed_const(non_frac + 1);
60 else
61 return dfixed_const(non_frac);
62 }
63
dfixed_div(fixed20_12 A,fixed20_12 B)64 static inline u32 dfixed_div(fixed20_12 A, fixed20_12 B)
65 {
66 u64 tmp = ((u64)A.full << 13);
67
68 do_div(tmp, B.full);
69 tmp += 1;
70 tmp /= 2;
71 return lower_32_bits(tmp);
72 }
73
74 #define DRM_FIXED_POINT 32
75 #define DRM_FIXED_ONE (1ULL << DRM_FIXED_POINT)
76 #define DRM_FIXED_DECIMAL_MASK (DRM_FIXED_ONE - 1)
77 #define DRM_FIXED_DIGITS_MASK (~DRM_FIXED_DECIMAL_MASK)
78 #define DRM_FIXED_EPSILON 1LL
79 #define DRM_FIXED_ALMOST_ONE (DRM_FIXED_ONE - DRM_FIXED_EPSILON)
80
drm_int2fixp(int a)81 static inline s64 drm_int2fixp(int a)
82 {
83 return ((s64)a) << DRM_FIXED_POINT;
84 }
85
drm_fixp2int(s64 a)86 static inline int drm_fixp2int(s64 a)
87 {
88 return ((s64)a) >> DRM_FIXED_POINT;
89 }
90
drm_fixp2int_ceil(s64 a)91 static inline int drm_fixp2int_ceil(s64 a)
92 {
93 if (a > 0)
94 return drm_fixp2int(a + DRM_FIXED_ALMOST_ONE);
95 else
96 return drm_fixp2int(a - DRM_FIXED_ALMOST_ONE);
97 }
98
drm_fixp_msbset(s64 a)99 static inline unsigned drm_fixp_msbset(s64 a)
100 {
101 unsigned shift, sign = (a >> 63) & 1;
102
103 for (shift = 62; shift > 0; --shift)
104 if (((a >> shift) & 1) != sign)
105 return shift;
106
107 return 0;
108 }
109
drm_fixp_mul(s64 a,s64 b)110 static inline s64 drm_fixp_mul(s64 a, s64 b)
111 {
112 unsigned shift = drm_fixp_msbset(a) + drm_fixp_msbset(b);
113 s64 result;
114
115 if (shift > 61) {
116 shift = shift - 61;
117 a >>= (shift >> 1) + (shift & 1);
118 b >>= shift >> 1;
119 } else
120 shift = 0;
121
122 result = a * b;
123
124 if (shift > DRM_FIXED_POINT)
125 return result << (shift - DRM_FIXED_POINT);
126
127 if (shift < DRM_FIXED_POINT)
128 return result >> (DRM_FIXED_POINT - shift);
129
130 return result;
131 }
132
drm_fixp_div(s64 a,s64 b)133 static inline s64 drm_fixp_div(s64 a, s64 b)
134 {
135 unsigned shift = 62 - drm_fixp_msbset(a);
136 s64 result;
137
138 a <<= shift;
139
140 if (shift < DRM_FIXED_POINT)
141 b >>= (DRM_FIXED_POINT - shift);
142
143 result = div64_s64(a, b);
144
145 if (shift > DRM_FIXED_POINT)
146 return result >> (shift - DRM_FIXED_POINT);
147
148 return result;
149 }
150
drm_fixp_from_fraction(s64 a,s64 b)151 static inline s64 drm_fixp_from_fraction(s64 a, s64 b)
152 {
153 s64 res;
154 bool a_neg = a < 0;
155 bool b_neg = b < 0;
156 u64 a_abs = a_neg ? -a : a;
157 u64 b_abs = b_neg ? -b : b;
158 u64 rem;
159
160 /* determine integer part */
161 u64 res_abs = div64_u64_rem(a_abs, b_abs, &rem);
162
163 /* determine fractional part */
164 {
165 u32 i = DRM_FIXED_POINT;
166
167 do {
168 rem <<= 1;
169 res_abs <<= 1;
170 if (rem >= b_abs) {
171 res_abs |= 1;
172 rem -= b_abs;
173 }
174 } while (--i != 0);
175 }
176
177 /* round up LSB */
178 {
179 u64 summand = (rem << 1) >= b_abs;
180
181 res_abs += summand;
182 }
183
184 res = (s64) res_abs;
185 if (a_neg ^ b_neg)
186 res = -res;
187 return res;
188 }
189
drm_fixp_exp(s64 x)190 static inline s64 drm_fixp_exp(s64 x)
191 {
192 s64 tolerance = div64_s64(DRM_FIXED_ONE, 1000000);
193 s64 sum = DRM_FIXED_ONE, term, y = x;
194 u64 count = 1;
195
196 if (x < 0)
197 y = -1 * x;
198
199 term = y;
200
201 while (term >= tolerance) {
202 sum = sum + term;
203 count = count + 1;
204 term = drm_fixp_mul(term, div64_s64(y, count));
205 }
206
207 if (x < 0)
208 sum = drm_fixp_div(DRM_FIXED_ONE, sum);
209
210 return sum;
211 }
212
213 #endif
214